1.
Particle
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A particle is a minute fragment or quantity of matter. In the physical sciences, a particle is a small localized object to which can be ascribed several physical or chemical properties such as volume or mass. Particles can also be used to create models of even larger objects depending on their density. The term particle is rather general in meaning, and is refined as needed by various scientific fields, something that is composed of particles may be referred to as being particulate. However, the particulate is most frequently used to refer to pollutants in the Earths atmosphere. The concept of particles is particularly useful when modelling nature, as the treatment of many phenomena can be complex. It can be used to make simplifying assumptions concerning the processes involved, francis Sears and Mark Zemansky, in University Physics, give the example of calculating the landing location and speed of a baseball thrown in the air. The treatment of large numbers of particles is the realm of statistical physics, the term particle is usually applied differently to three classes of sizes. The term macroscopic particle, usually refers to particles much larger than atoms and these are usually abstracted as point-like particles, or even invisible. This is even though they have volumes, shapes, structures, examples of macroscopic particles would include powder, dust, sand, pieces of debris during a car accident, or even objects as big as the stars of a galaxy. Another type, microscopic particles usually refers to particles of sizes ranging from atoms to molecules, such as carbon dioxide, nanoparticles and these particles are studied in chemistry, as well as atomic and molecular physics. The smallest of particles are the particles, which refer to particles smaller than atoms. These particles are studied in particle physics, because of their extremely small size, the study of microscopic and subatomic particles fall in the realm of quantum mechanics. Particles can also be classified according to composition, composite particles refer to particles that have composition – that is particles which are made of other particles. For example, an atom is made of six protons, eight neutrons. By contrast, elementary particles refer to particles that are not made of other particles, according to our current understanding of the world, only a very small number of these exist, such as the leptons, quarks or gluons. However it is possible some of these might turn up to be composite particles after all. While composite particles can very often be considered point-like, elementary particles are truly punctual, both elementary and composite particles, are known to undergo particle decay
2.
Particle statistics
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Particle statistics is a particular description of multiple particles in statistical mechanics. Its core concept is an ensemble that emphasizes properties of a large system as a whole at the expense of knowledge about parameters of separate particles. When an ensemble consists of particles with similar properties, their number is called the particle number, in classical mechanics, all particles in the system are considered distinguishable. This means that particles in a system can be tracked. As a consequence, changing the position of any two particles in the leads to a completely different configuration of the entire system. Furthermore, there is no restriction on placing more than one particle in any given state accessible to the system and these characteristics of classical positions are called Maxwell–Boltzmann statistics. The fundamental feature of quantum mechanics that distinguishes it from classical mechanics is that particles of a type are indistinguishable from one another. This means that in an assembly consisting of particles, interchanging any two particles does not lead to a new configuration of the system. In the case of a system consisting of particles of different kinds, all quantum particles, such as leptons and baryons, in the universe have three translational motion degrees of freedom and one discrete degree of freedom, known as spin. Thats why quantum statistics is useful when one considers, say, helium liquid or ammonia gas, the spin–statistics theorem binds two particular kinds of combinatorial symmetry with two particular kinds of spin symmetry, namely bosons and fermions. In Bose–Einstein statistics interchanging any two particles of the leaves the resultant system in a symmetric state. That is, the function of the system before interchanging equals the wave function of the system after interchanging. It is important to emphasize that the function of the system has not changed itself. This has very important consequences on the state of the system and it is found that the particles that obey Bose–Einstein statistics are the ones which have integer spins, which are therefore called bosons. Examples of bosons include photons and helium-4, one type of system obeying B–E statistics is the Bose–Einstein condensate where all particles of the assembly exist in the same state. In Fermi–Dirac statistics interchanging any two particles of the leaves the resultant system in an antisymmetric state. That is, the function of the system before interchanging is the wave function of the system after interchanging. Again, the function of the system itself does not change
3.
Fundamental interaction
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In physics, the fundamental interactions, also known as fundamental forces, are the interactions that do not appear to be reducible to more basic interactions. There are four conventionally accepted fundamental interactions—gravitational, electromagnetic, strong, each one is described mathematically as a field. The gravitational force is modelled as a classical field. The other three, part of the Standard Model of particle physics, are described as discrete quantum fields, and their interactions are carried by a quantum. The strong and weak interactions have short ranges, producing forces at minuscule, subatomic distances, the strong interaction, which is carried by the gluon particle, is responsible for the binding of quarks together to form hadrons, such as protons and neutrons. As a residual effect, it creates the force that binds the latter particles to form atomic nuclei. The weak interaction, which is carried by the W and Z particles, also acts on the nucleus, the other two, electromagnetism and gravity, produce significant forces at macroscopic scales where the effects can be seen directly in everyday life. The electromagnetic force, carried by the photon, creates electric and magnetic fields, Electromagnetic forces tend to cancel each other out when large collections of objects are considered, so over the largest distances, gravity tends to be the dominant force. Other theorists seek to unite the electroweak and strong fields within a Grand Unified Theory, some theories, notably string theory, seek both QG and GUT within one framework, unifying all four fundamental interactions along with mass generation within a theory of everything. A few researchers have interpreted various anomalous observations in physics as evidence for a fifth force, inferring that all objects bearing mass approach at a constant rate, but collide by impact proportional to their masses, Newton inferred that matter exhibits an attractive force. Thus Newtons theory violated the first principle of mechanical philosophy, as stated by Descartes, conversely, during the 1820s, when explaining magnetism, Michael Faraday inferred a field filling space and transmitting that force. Faraday conjectured that ultimately, all unified into one. In the early 1870s, James Clerk Maxwell unified electricity and magnetism as effects of a field whose third consequence was light. The Standard Model of particle physics was developed throughout the half of the 20th century. In the Standard Model, the electromagnetic, strong, and weak interactions associate with elementary particles, for predictive success with QMs probabilistic outcomes, particle physics conventionally models QM events across a field set to special relativity, altogether relativistic quantum field theory. Force particles, called gauge bosons—force carriers or messenger particles of underlying fields—interact with matter particles, everyday matter is atoms, composed of three fermion types, up-quarks and down-quarks constituting, as well as electrons orbiting, the atoms nucleus. The electromagnetic interaction was modelled with the interaction, whose force carriers are W and Z bosons, traversing the minuscule distance. Electroweak interaction would operate at high temperatures as soon after the presumed Big Bang
4.
Strong interaction
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At the range of 10−15 m, the strong force is approximately 137 times as strong as electromagnetism, a million times as strong as the weak interaction and 1038 times as strong as gravitation. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as proton and neutron, in addition, the strong force binds neutrons and protons to create atomic nuclei. Most of the mass of a proton or neutron is the result of the strong force field energy. The strong interaction is observable at two ranges, on a scale, it is the force that binds protons and neutrons together to form the nucleus of an atom. On the smaller scale, it is the force that holds together to form protons, neutrons. In the latter context, it is known as the color force. The strong force inherently has such a strength that hadrons bound by the strong force can produce new massive particles. Thus, if hadrons are struck by particles, they give rise to new hadrons instead of emitting freely moving radiation. This property of the force is called color confinement, and it prevents the free emission of the strong force, instead, in practice. In the context of binding protons and neutrons together to form atomic nuclei, in this case, it is the residuum of the strong interaction between the quarks that make up the protons and neutrons. As such, the strong interaction obeys a quite different distance-dependent behavior between nucleons, from when it is acting to bind quarks within nucleons. The binding energy that is released on the breakup of a nucleus is related to the residual strong force and is harnessed as fission energy in nuclear power. The strong interaction is mediated by the exchange of particles called gluons that act between quarks, antiquarks, and other gluons. Gluons are thought to interact with quarks and other gluons by way of a type of charge called color charge. Color charge is analogous to electromagnetic charge, but it comes in three rather than one, which results in a different type of force, with different rules of behavior. These rules are detailed in the theory of quantum chromodynamics, which is the theory of quark-gluon interactions, after the Big Bang and during the electroweak epoch of the universe, the electroweak force separated from the strong force. A Grand Unified Theory is hypothesized to exist to describe this, but no theory has yet been successfully formulated. Before the 1970s, physicists were uncertain as to how the nucleus was bound together
5.
Weak interaction
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In particle physics, the weak interaction is one of the four known fundamental interactions of nature, alongside the strong interaction, electromagnetism, and gravitation. The weak interaction is responsible for radioactive decay, which plays an role in nuclear fission. The theory of the interaction is sometimes called quantum flavourdynamics, in analogy with the terms QCD dealing with the strong interaction. However the term QFD is rarely used because the force is best understood in terms of electro-weak theory. The Standard Model of particle physics, which does not address gravity, provides a framework for understanding how the electromagnetic, weak. An interaction occurs when two particles, typically but not necessarily half-integer spin fermions, exchange integer-spin, force-carrying bosons, the fermions involved in such exchanges can be either elementary or composite, although at the deepest levels, all weak interactions ultimately are between elementary particles. In the case of the interaction, fermions can exchange three distinct types of force carriers known as the W+, W−, and Z bosons. The mass of each of these bosons is far greater than the mass of a proton or neutron, the force is in fact termed weak because its field strength over a given distance is typically several orders of magnitude less than that of the strong nuclear force or electromagnetic force. During the quark epoch of the universe, the electroweak force separated into the electromagnetic. Important examples of the weak interaction include beta decay, and the fusion of hydrogen into deuterium that powers the Suns thermonuclear process, most fermions will decay by a weak interaction over time. Such decay makes radiocarbon dating possible, as carbon-14 decays through the interaction to nitrogen-14. It can also create radioluminescence, commonly used in tritium illumination, quarks, which make up composite particles like neutrons and protons, come in six flavours – up, down, strange, charm, top and bottom – which give those composite particles their properties. The weak interaction is unique in that it allows for quarks to swap their flavour for another, the swapping of those properties is mediated by the force carrier bosons. Also, the interaction is the only fundamental interaction that breaks parity-symmetry, and similarly. In 1933, Enrico Fermi proposed the first theory of the weak interaction and he suggested that beta decay could be explained by a four-fermion interaction, involving a contact force with no range. However, it is described as a non-contact force field having a finite range. The existence of the W and Z bosons was not directly confirmed until 1983, the weak interaction is unique in a number of respects, It is the only interaction capable of changing the flavour of quarks. It is the interaction that violates P or parity-symmetry
6.
Electromagnetic interaction
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Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually exhibits electromagnetic fields such as fields, magnetic fields. The other three fundamental interactions are the interaction, the weak interaction, and gravitation. The word electromagnetism is a form of two Greek terms, ἤλεκτρον, ēlektron, amber, and μαγνῆτις λίθος magnētis lithos, which means magnesian stone. The electromagnetic force plays a role in determining the internal properties of most objects encountered in daily life. Ordinary matter takes its form as a result of forces between individual atoms and molecules in matter, and is a manifestation of the electromagnetic force. Electrons are bound by the force to atomic nuclei, and their orbital shapes. The electromagnetic force governs the processes involved in chemistry, which arise from interactions between the electrons of neighboring atoms, there are numerous mathematical descriptions of the electromagnetic field. In classical electrodynamics, electric fields are described as electric potential, although electromagnetism is considered one of the four fundamental forces, at high energy the weak force and electromagnetic force are unified as a single electroweak force. In the history of the universe, during the epoch the unified force broke into the two separate forces as the universe cooled. Originally, electricity and magnetism were considered to be two separate forces, Magnetic poles attract or repel one another in a manner similar to positive and negative charges and always exist as pairs, every north pole is yoked to a south pole. An electric current inside a wire creates a corresponding magnetic field outside the wire. Its direction depends on the direction of the current in the wire. A current is induced in a loop of wire when it is moved toward or away from a field, or a magnet is moved towards or away from it. While preparing for a lecture on 21 April 1820, Hans Christian Ørsted made a surprising observation. As he was setting up his materials, he noticed a compass needle deflected away from north when the electric current from the battery he was using was switched on. At the time of discovery, Ørsted did not suggest any explanation of the phenomenon. However, three later he began more intensive investigations
7.
Gravity
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Gravity, or gravitation, is a natural phenomenon by which all things with mass are brought toward one another, including planets, stars and galaxies. Since energy and mass are equivalent, all forms of energy, including light, on Earth, gravity gives weight to physical objects and causes the ocean tides. Gravity has a range, although its effects become increasingly weaker on farther objects. The most extreme example of this curvature of spacetime is a hole, from which nothing can escape once past its event horizon. More gravity results in time dilation, where time lapses more slowly at a lower gravitational potential. Gravity is the weakest of the four fundamental interactions of nature, the gravitational attraction is approximately 1038 times weaker than the strong force,1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, gravity has an influence on the behavior of subatomic particles. On the other hand, gravity is the dominant interaction at the macroscopic scale, for this reason, in part, pursuit of a theory of everything, the merging of the general theory of relativity and quantum mechanics into quantum gravity, has become an area of research. While the modern European thinkers are credited with development of gravitational theory, some of the earliest descriptions came from early mathematician-astronomers, such as Aryabhata, who had identified the force of gravity to explain why objects do not fall out when the Earth rotates. Later, the works of Brahmagupta referred to the presence of force, described it as an attractive force. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and this was a major departure from Aristotles belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass may fall slower in an atmosphere, galileos work set the stage for the formulation of Newtons theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. Newtons theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the position of the planet. A discrepancy in Mercurys orbit pointed out flaws in Newtons theory, the issue was resolved in 1915 by Albert Einsteins new theory of general relativity, which accounted for the small discrepancy in Mercurys orbit. The simplest way to test the equivalence principle is to drop two objects of different masses or compositions in a vacuum and see whether they hit the ground at the same time. Such experiments demonstrate that all objects fall at the rate when other forces are negligible
8.
Hideki Yukawa
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Hideki Yukawa ForMemRS FRSE, was a Japanese theoretical physicist and the first Japanese Nobel laureate. He was born as Hideki Ogawa in Tokyo and grew up in Kyoto with two brothers, two older sisters, and two younger brothers. He read the Confucian Doctrine of the Mean, and later Lao-Tzu and Chuang-Tzu and his father, for a time, considered sending him to technical college rather than university since he was not as outstanding a student as his older brothers. Ogawa decided against becoming a mathematician when in school, his teacher marked his exam answer as incorrect when Ogawa proved a theorem. He decided against a career in physics in college when he demonstrated clumsiness in glassblowing. In 1929, after receiving his degree from Kyoto Imperial University, after graduation, he was interested in theoretical physics, particularly in the theory of elementary particles. In 1932, he married Sumi Yukawa, the couple had two sons, Harumi and Takaaki. In 1933 he became an assistant professor at, at 26 years old, in 1935 he published his theory of mesons, which explained the interaction between protons and neutrons, and was a major influence on research into elementary particles. In 1940 he became a professor in Kyoto University, in 1940 he won the Imperial Prize of the Japan Academy, in 1943 the Decoration of Cultural Merit from the Japanese government. Yukawa also worked on the theory of K-capture, in which a low energy electron is absorbed by the nucleus, Yukawa became the first chairman of Yukawa Institute for Theoretical Physics in 1953. He was an editor of Progress of Theoretical Physics, and published the books Introduction to Quantum Mechanics, in 1955, he joined ten other leading scientists and intellectuals in signing the Russell–Einstein Manifesto, calling for nuclear disarmament. Yukawa retired from Kyoto University in 1970 as a Professor Emeritus, owing to increasing infirmity, in his final years he appeared in public in a wheelchair. He died at his home in Sakyo-ku, Kyoto, on 8 September 1981 from pneumonia and heart failure and his tomb is in Higashiyama-ku, Kyoto. Solo violinist Diana Yukawa is a relative of Hideki Yukawa
9.
Giuseppe Occhialini
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Giuseppe Paolo Stanislao Beppo Occhialini ForMemRS was an Italian physicist, who contributed to the discovery of the pion or pi-meson decay in 1947, with César Lattes and Cecil Frank Powell. At the time of discovery, they were all working at the H. H. Wills Laboratory of the University of Bristol, the X-ray satellite SAX was named BeppoSAX in his honour after its launch in 1996. His father was the physicist Raffaele Augusto Occhialini, pioneer in the fields of spectroscopy, Giuseppe Paolo Stanislao Occhialini graduated at Florence in 1929. In 1932, he collaborated in the discovery of the positron in cosmic rays at the Cavendish Laboratory of Cambridge, under the leadership of Patrick Blackett, using cloud chambers. From 1937 to the 1944 he worked, on invitation of Gleb Wataghin, at the institute of physics of the University of São Paulo and he returned to Italy, in 1944, taught first in Genoa and then in Milan. In 1947 he contributed to the discovery of the pion or pi-meson decay in collaboration with César Lattes, the discovery was made at the Wills Laboratory of Bristol using the technology of the tracks on specialized photographic emulsions. Later on with the coming of particle accelerators, Occhialini explored that new field of research and he also made outstanding contributions to space physics, importantly contributing to the foundation of the European Space Agency. The Department of Physics of University of Milan Bicocca, active since 1997, is named after him, the satellite SAX, the first Italian satellite for the study of gamma rays, was renamed BeppoSAX from his nickname Beppo. An asteroid,20081 Occhialini was named for him, in 1949 he received the National Prize of the President of the Republic. In 1979 he was awarded the Wolf Prize for physics, antonio Vitale, Ordinary Professor of Physics at the University of Bologna, created the Foundation Giuseppe Occhialini with its seat at Fossombrone, birth town of Giuseppe Occhialini. In 2007 the Italian Physical Society together with the Institute of Physics instituted the Occhialini Prize to honour his memory, on 22 June 2009 a Milans square was named after him, that same square where the Institute of Physics was at the time he first became professor there. Beppo Occhialini was a mountain climber. During WW II, staying in Brazil, then a country hostile to Italy, he became an alpine guide in the Parque Nacional do Itatiaia. The Scientific Legacy of Beppo Occhialini, Bologna, Società Italiana di Fisica, Springer,2006. Istituto Nazionale di Astrofisica – Italy
10.
Cecil Powell
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Following this he attended Sidney Sussex College, Cambridge, graduating in 1925 in the natural sciences. After completing his bachelors degree he worked at the Cavendish Laboratory, Cambridge, wilson and Lord Rutherford, conducting research into condensation phenomena, and gaining his Ph. D. in Physics in 1927. In 1928 he took up a post as Research Assistant to A. M, tyndall in the H. H. Wills Physical Laboratory at the University of Bristol, later being appointed lecturer, and in 1948 appointed Melville Wills Professor of Physics. In 1932 Powell married Isobel Artner, and the couple had two daughters, in 1936 he took part in an expedition to the West Indies as part of a study of volcanic activity, and where he appears on a stamp issued in Grenada. Muirhead and young Brazilian physicist César Lattes and this work led in 1946 to the discovery of the pion, which proved to be the hypothetical particle proposed in 1935 by Yukawa Hideki in his theory of nuclear physics. In 1949 Powell became a Fellow of the Royal Society and received the societys Hughes Medal the same year, in 1950 he was awarded the Nobel Prize for Physics for his development of the photographic method of studying nuclear processes and his discoveries regarding mesons made with this method. From 1952 Powell was appointed director of several expeditions to Sardinia, as Rotblat put it, Cecil Powell has been the backbone of the Pugwash Movement. He gave it coherence, endurance and vitality, Powell chaired the meetings of the Pugwash Continuing Committee, often standing in for Bertrand Russell, and attended meetings until 1968. Powell died on 9 August 1969, whilst out walking in the foothills of the Alps near the Valsassina region of Italy, a bench with commemorative plaque was erected near the site of his death. The Cecil F. Powell Memorial Medal was named in his honour by the European Physical Society, marietta Blau Page on Powell on the Nobel site, including biography, speeches, and lecture Portrait photograph of Powell at the American Institute of Physics
11.
Invariant mass
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More precisely, it is a characteristic of the systems total energy and momentum that is the same in all frames of reference related by Lorentz transformations. If a center of momentum frame exists for the system, then the invariant mass of a system is equal to its mass in that rest frame. In other reference frames, where the momentum is nonzero, the total mass of the system is greater than the invariant mass. Due to mass-energy equivalence, the rest energy of the system is simply the invariant mass times the speed of light squared, similarly, the total energy of the system is its total mass times the speed of light squared. Systems whose four-momentum is a null vector have zero invariant mass, a physical object or particle moving faster than the speed of light would have space-like four-momenta, and these do not appear to exist. Any time-like four-momentum possesses a frame where the momentum is zero. In this case, invariant mass is positive and is referred to as the rest mass, if objects within a system are in relative motion, then the invariant mass of the whole system will differ from the sum of the objects rest masses. This is also equal to the energy of the system divided by c2. See mass–energy equivalence for a discussion of definitions of mass, for example, a scale would measure the kinetic energy of the molecules in a bottle of gas to be part of invariant mass of the bottle, and thus also its rest mass. The same is true for massless particles in such system, which add invariant mass and also rest mass to systems, for an isolated massive system, the center of mass of the system moves in a straight line with a steady sub-luminal velocity. Thus, an observer can always be placed to move along with it. In this frame, which is the center of momentum frame, the momentum is zero. In this frame, which exists under these assumptions, the invariant mass of the system is equal to the system energy divided by c2. This total energy in the center of momentum frame, is the energy which the system may be observed to have. Note that for reasons above, such a rest frame does not exist for single photons, when two or more photons move in different directions, however, a center of mass frame exists. Thus, the mass of a system of several photons moving in different directions is positive, for example, rest mass and invariant mass are zero for individual photons even though they may add mass to the invariant mass of systems. For this reason, invariant mass is in not an additive quantity. Consider the simple case of system, where object A is moving towards another object B which is initially at rest
12.
Electronvolt
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In physics, the electronvolt is a unit of energy equal to approximately 1. 6×10−19 joules. By definition, it is the amount of energy gained by the charge of an electron moving across an electric potential difference of one volt. Thus it is 1 volt multiplied by the elementary charge, therefore, one electronvolt is equal to 6981160217662079999♠1. 6021766208×10−19 J. The electronvolt is not a SI unit, and its definition is empirical, like the elementary charge on which it is based, it is not an independent quantity but is equal to 1 J/C √2hα / μ0c0. It is a unit of energy within physics, widely used in solid state, atomic, nuclear. It is commonly used with the metric prefixes milli-, kilo-, in some older documents, and in the name Bevatron, the symbol BeV is used, which stands for billion electronvolts, it is equivalent to the GeV. By mass–energy equivalence, the electronvolt is also a unit of mass and it is common in particle physics, where units of mass and energy are often interchanged, to express mass in units of eV/c2, where c is the speed of light in vacuum. It is common to express mass in terms of eV as a unit of mass. The mass equivalent of 1 eV/c2 is 1 eV / c 2 = ⋅1 V2 =1.783 ×10 −36 kg. For example, an electron and a positron, each with a mass of 0.511 MeV/c2, the proton has a mass of 0.938 GeV/c2. In general, the masses of all hadrons are of the order of 1 GeV/c2, the unified atomic mass unit,1 gram divided by Avogadros number, is almost the mass of a hydrogen atom, which is mostly the mass of the proton. To convert to megaelectronvolts, use the formula,1 u =931.4941 MeV/c2 =0.9314941 GeV/c2, in high-energy physics, the electronvolt is often used as a unit of momentum. A potential difference of 1 volt causes an electron to gain an amount of energy and this gives rise to usage of eV as units of momentum, for the energy supplied results in acceleration of the particle. The dimensions of units are LMT−1. The dimensions of units are L2MT−2. Then, dividing the units of energy by a constant that has units of velocity. In the field of particle physics, the fundamental velocity unit is the speed of light in vacuum c. Thus, dividing energy in eV by the speed of light, the fundamental velocity constant c is often dropped from the units of momentum by way of defining units of length such that the value of c is unity
13.
Electric charge
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Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of charges, positive and negative. Like charges repel and unlike attract, an absence of net charge is referred to as neutral. An object is charged if it has an excess of electrons. The SI derived unit of charge is the coulomb. In electrical engineering, it is common to use the ampere-hour. The symbol Q often denotes charge, early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that dont require consideration of quantum effects. The electric charge is a conserved property of some subatomic particles. Electrically charged matter is influenced by, and produces, electromagnetic fields, the interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces. 602×10−19 coulombs. The proton has a charge of +e, and the electron has a charge of −e, the study of charged particles, and how their interactions are mediated by photons, is called quantum electrodynamics. Charge is the property of forms of matter that exhibit electrostatic attraction or repulsion in the presence of other matter. Electric charge is a property of many subatomic particles. The charges of free-standing particles are integer multiples of the charge e. Michael Faraday, in his electrolysis experiments, was the first to note the discrete nature of electric charge, robert Millikans oil drop experiment demonstrated this fact directly, and measured the elementary charge. By convention, the charge of an electron is −1, while that of a proton is +1, charged particles whose charges have the same sign repel one another, and particles whose charges have different signs attract. The charge of an antiparticle equals that of the corresponding particle, quarks have fractional charges of either −1/3 or +2/3, but free-standing quarks have never been observed. The electric charge of an object is the sum of the electric charges of the particles that make it up. An ion is an atom that has lost one or more electrons, giving it a net charge, or that has gained one or more electrons
14.
Spin (physics)
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In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles, and atomic nuclei. Spin is one of two types of angular momentum in mechanics, the other being orbital angular momentum. In some ways, spin is like a vector quantity, it has a definite magnitude, all elementary particles of a given kind have the same magnitude of spin angular momentum, which is indicated by assigning the particle a spin quantum number. The SI unit of spin is the or, just as with classical angular momentum, very often, the spin quantum number is simply called spin leaving its meaning as the unitless spin quantum number to be inferred from context. When combined with the theorem, the spin of electrons results in the Pauli exclusion principle. Wolfgang Pauli was the first to propose the concept of spin, in 1925, Ralph Kronig, George Uhlenbeck and Samuel Goudsmit at Leiden University suggested an physical interpretation of particles spinning around their own axis. The mathematical theory was worked out in depth by Pauli in 1927, when Paul Dirac derived his relativistic quantum mechanics in 1928, electron spin was an essential part of it. As the name suggests, spin was originally conceived as the rotation of a particle around some axis and this picture is correct so far as spin obeys the same mathematical laws as quantized angular momenta do. On the other hand, spin has some properties that distinguish it from orbital angular momenta. Although the direction of its spin can be changed, a particle cannot be made to spin faster or slower. The spin of a particle is associated with a magnetic dipole moment with a g-factor differing from 1. This could only occur if the internal charge of the particle were distributed differently from its mass. The conventional definition of the quantum number, s, is s = n/2. Hence the allowed values of s are 0, 1/2,1, 3/2,2, the value of s for an elementary particle depends only on the type of particle, and cannot be altered in any known way. The spin angular momentum, S, of any system is quantized. The allowed values of S are S = ℏ s = h 4 π n, in contrast, orbital angular momentum can only take on integer values of s, i. e. even-numbered values of n. Those particles with half-integer spins, such as 1/2, 3/2, 5/2, are known as fermions, while particles with integer spins. The two families of particles obey different rules and broadly have different roles in the world around us, a key distinction between the two families is that fermions obey the Pauli exclusion principle, that is, there cannot be two identical fermions simultaneously having the same quantum numbers
15.
Parity (physics)
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In quantum mechanics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is often described by the simultaneous flip in the sign of all three spatial coordinates, P, ↦. It can also be thought of as a test for chirality of a physical phenomenon, a parity transformation on something achiral, on the other hand, can be viewed as an identity transformation. All fundamental interactions of particles, with the exception of the weak interaction, are symmetric under parity. The weak interaction is chiral and thus provides a means for probing chirality in physics, in interactions that are symmetric under parity, such as electromagnetism in atomic and molecular physics, parity serves as a powerful controlling principle underlying quantum transitions. A matrix representation of P has determinant equal to −1, and hence is distinct from a rotation, in a two-dimensional plane, a simultaneous flip of all coordinates in sign is not a parity transformation, it is the same as a 180°-rotation. Under rotations, classical geometrical objects can be classified into scalars, vectors, in classical physics, physical configurations need to transform under representations of every symmetry group. Quantum theory predicts that states in a Hilbert space do not need to transform under representations of the group of rotations, the projective representations of any group are isomorphic to the ordinary representations of a central extension of the group. For example, projective representations of the 3-dimensional rotation group, which is the orthogonal group SO, are ordinary representations of the special unitary group SU. Projective representations of the group that are not representations are called spinors. If one adds to this a classification by parity, these can be extended, for example, vectors and axial vectors which both transform as vectors under rotation. One can define reflections such as V x, ↦, which also have negative determinant, then, combining them with rotations one can recover the particular parity transformation defined earlier. The first parity transformation given does not work in an number of dimensions, though. In odd number of only the latter example of a parity transformation can be used. Parity forms the abelian group Z2 due to the relation P2 =1, all Abelian groups have only one-dimensional irreducible representations. For Z2, there are two representations, one is even under parity, the other is odd. These are useful in quantum mechanics, newtons equation of motion F = ma equates two vectors, and hence is invariant under parity. The law of gravity also involves only vectors and is also, therefore, however, angular momentum L is an axial vector, L = r × p, P = × = L
16.
Particle physics
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Particle physics is the branch of physics that studies the nature of the particles that constitute matter and radiation. By our current understanding, these particles are excitations of the quantum fields that also govern their interactions. The currently dominant theory explaining these fundamental particles and fields, along with their dynamics, is called the Standard Model, in more technical terms, they are described by quantum state vectors in a Hilbert space, which is also treated in quantum field theory. All particles and their interactions observed to date can be described almost entirely by a field theory called the Standard Model. The Standard Model, as formulated, has 61 elementary particles. Those elementary particles can combine to form composite particles, accounting for the hundreds of species of particles that have been discovered since the 1960s. The Standard Model has been found to agree with almost all the tests conducted to date. However, most particle physicists believe that it is a description of nature. In recent years, measurements of mass have provided the first experimental deviations from the Standard Model. The idea that all matter is composed of elementary particles dates from at least the 6th century BC, in the 19th century, John Dalton, through his work on stoichiometry, concluded that each element of nature was composed of a single, unique type of particle. Throughout the 1950s and 1960s, a variety of particles were found in collisions of particles from increasingly high-energy beams. It was referred to informally as the particle zoo, the current state of the classification of all elementary particles is explained by the Standard Model. It describes the strong, weak, and electromagnetic fundamental interactions, the species of gauge bosons are the gluons, W−, W+ and Z bosons, and the photons. The Standard Model also contains 24 fundamental particles, which are the constituents of all matter, finally, the Standard Model also predicted the existence of a type of boson known as the Higgs boson. Early in the morning on 4 July 2012, physicists with the Large Hadron Collider at CERN announced they had found a new particle that behaves similarly to what is expected from the Higgs boson, the worlds major particle physics laboratories are, Brookhaven National Laboratory. Its main facility is the Relativistic Heavy Ion Collider, which collides heavy ions such as gold ions and it is the worlds first heavy ion collider, and the worlds only polarized proton collider. Its main projects are now the electron-positron colliders VEPP-2000, operated since 2006 and its main project is now the Large Hadron Collider, which had its first beam circulation on 10 September 2008, and is now the worlds most energetic collider of protons. It also became the most energetic collider of heavy ions after it began colliding lead ions and its main facility is the Hadron Elektron Ring Anlage, which collides electrons and positrons with protons
17.
Greek alphabet
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It is the ancestor of the Latin and Cyrillic scripts. In its classical and modern forms, the alphabet has 24 letters, Modern and Ancient Greek use different diacritics. In standard Modern Greek spelling, orthography has been simplified to the monotonic system, examples In both Ancient and Modern Greek, the letters of the Greek alphabet have fairly stable and consistent symbol-to-sound mappings, making pronunciation of words largely predictable. Ancient Greek spelling was generally near-phonemic, among consonant letters, all letters that denoted voiced plosive consonants and aspirated plosives in Ancient Greek stand for corresponding fricative sounds in Modern Greek. This leads to groups of vowel letters denoting identical sounds today. Modern Greek orthography remains true to the spellings in most of these cases. The following vowel letters and digraphs are involved in the mergers, Modern Greek speakers typically use the same, modern, in other countries, students of Ancient Greek may use a variety of conventional approximations of the historical sound system in pronouncing Ancient Greek. Several letter combinations have special conventional sound values different from those of their single components, among them are several digraphs of vowel letters that formerly represented diphthongs but are now monophthongized. In addition to the three mentioned above, there is also ⟨ου⟩, pronounced /u/, the Ancient Greek diphthongs ⟨αυ⟩, ⟨ευ⟩ and ⟨ηυ⟩ are pronounced, and respectively in voicing environments in Modern Greek. The Modern Greek consonant combinations ⟨μπ⟩ and ⟨ντ⟩ stand for and respectively, ⟨τζ⟩ stands for, in addition, both in Ancient and Modern Greek, the letter ⟨γ⟩, before another velar consonant, stands for the velar nasal, thus ⟨γγ⟩ and ⟨γκ⟩ are pronounced like English ⟨ng⟩. There are also the combinations ⟨γχ⟩ and ⟨γξ⟩ and these signs were originally designed to mark different forms of the phonological pitch accent in Ancient Greek. The letter rho, although not a vowel, also carries a rough breathing in word-initial position, if a rho was geminated within a word, the first ρ always had the smooth breathing and the second the rough breathing leading to the transiliteration rrh. The vowel letters ⟨α, η, ω⟩ carry an additional diacritic in certain words, the iota subscript. This iota represents the former offglide of what were originally long diphthongs, ⟨ᾱι, ηι, ωι⟩, another diacritic used in Greek is the diaeresis, indicating a hiatus. In 1982, a new, simplified orthography, known as monotonic, was adopted for use in Modern Greek by the Greek state. Although it is not a diacritic, the comma has a function as a silent letter in a handful of Greek words, principally distinguishing ό. There are many different methods of rendering Greek text or Greek names in the Latin script, the form in which classical Greek names are conventionally rendered in English goes back to the way Greek loanwords were incorporated into Latin in antiquity. In this system, ⟨κ⟩ is replaced with ⟨c⟩, the diphthongs ⟨αι⟩ and ⟨οι⟩ are rendered as ⟨ae⟩ and ⟨oe⟩ respectively, and ⟨ει⟩ and ⟨ου⟩ are simplified to ⟨i⟩ and ⟨u⟩ respectively
18.
Pi (letter)
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Pi is the sixteenth letter of the Greek alphabet, representing. In the system of Greek numerals it has a value of 80 and it was derived from the Phoenician letter Pe. Letters that arose from pi include Cyrillic Pe, Coptic pi, the upper-case letter Π is used as a symbol for, The product operator in mathematics, indicated with capital pi notation ∏. In textual criticism, Codex Petropolitanus, a 9th-century, uncial codex of the Gospels, now located in St. Petersburg, in legal shorthand, it represents a plaintiff. The letter π is the first letter of the Greek words περιφέρεια periphery and περίμετρος perimeter, dimensionless parameters constructed using the Buckingham π theorem of dimensional analysis. The hadron called the pi meson or pion, a type of chemical bond in which the P-orbitals overlap, called a pi bond. The natural projection on the tangent bundle on a manifold, the unary operation of projection in relational algebra. In reinforcement learning π denotes policy, an early form of pi was, appearing almost like a gamma with a hook. In the book Lalphabet grec, T. H. de Mortain speculates that letter П is a gate, allegedly, the Greeks wanted to represent the shape of the entrance to civilization, such as the gate of the lions in Mycenae. This hypothesis is not shared by any authority in the field and has no other attestation. It is used as a symbol for, Angular frequency of a wave, longitude of pericenter, in celestial mechanics. Mean Fitness of a population in Biology, Greek / Coptic Pi Mathematical Pi These characters are used only as mathematical symbols. Stylized Greek text should be encoded using the normal Greek letters, with markup, П, п - Pe Р, р - Er P, p - Pe Greek letters used in mathematics, science, and engineering#Ππ Pilcrow - an unrelated but similar looking glyph
19.
Subatomic particle
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In the physical sciences, subatomic particles are particles much smaller than atoms. There are two types of particles, elementary particles, which according to current theories are not made of other particles. Particle physics and nuclear physics study these particles and how they interact, in particle physics, the concept of a particle is one of several concepts inherited from classical physics. But it also reflects the understanding that at the quantum scale matter. The idea of a particle underwent serious rethinking when experiments showed that light could behave like a stream of particles as well as exhibit wave-like properties and this led to the new concept of wave–particle duality to reflect that quantum-scale particles behave like both particles and waves. Another new concept, the uncertainty principle, states that some of their properties taken together, such as their simultaneous position and momentum, in more recent times, wave–particle duality has been shown to apply not only to photons but to increasingly massive particles as well. Interactions of particles in the framework of field theory are understood as creation and annihilation of quanta of corresponding fundamental interactions. This blends particle physics with field theory, any subatomic particle, like any particle in the 3-dimensional space that obeys laws of quantum mechanics, can be either a boson or a fermion. Various extensions of the Standard Model predict the existence of a graviton particle. Composite subatomic particles are bound states of two or more elementary particles, for example, a proton is made of two up quarks and one down quark, while the atomic nucleus of helium-4 is composed of two protons and two neutrons. The neutron is made of two quarks and one up quark. Composite particles include all hadrons, these include baryons and mesons, in special relativity, the energy of a particle at rest equals its mass times the speed of light squared, E = mc2. That is, mass can be expressed in terms of energy, if a particle has a frame of reference where it lies at rest, then it has a positive rest mass and is referred to as massive. Baryons tend to have greater mass than mesons, which in turn tend to be heavier than leptons and it is also certain that any particle with an electric charge is massive. These include the photon and gluon, although the latter cannot be isolated, through the work of Albert Einstein, Satyendra Nath Bose, Louis de Broglie, and many others, current scientific theory holds that all particles also have a wave nature. This has been verified not only for elementary particles but also for compound particles like atoms, interactions between particles have been scrutinized for many centuries, and a few simple laws underpin how particles behave in collisions and interactions. These are the basics of Newtonian mechanics, a series of statements and equations in Philosophiae Naturalis Principia Mathematica. The negatively charged electron has an equal to 1⁄1837 or 1836 of that of a hydrogen atom
20.
Quark
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A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation, they can be found only within hadrons, such as baryons and mesons. For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves, Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. There are six types of quarks, known as flavors, up, down, strange, charm, top, up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay, the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions. For every quark flavor there is a type of antiparticle, known as an antiquark. The quark model was proposed by physicists Murray Gell-Mann and George Zweig in 1964. Accelerator experiments have provided evidence for all six flavors, the top quark was the last to be discovered at Fermilab in 1995. The Standard Model is the theoretical framework describing all the known elementary particles. This model contains six flavors of quarks, named up, down, strange, charm, bottom, antiparticles of quarks are called antiquarks, and are denoted by a bar over the symbol for the corresponding quark, such as u for an up antiquark. As with antimatter in general, antiquarks have the mass, mean lifetime, and spin as their respective quarks. Quarks are spin- 1⁄2 particles, implying that they are fermions according to the spin-statistics theorem and they are subject to the Pauli exclusion principle, which states that no two identical fermions can simultaneously occupy the same quantum state. This is in contrast to bosons, any number of which can be in the same state, unlike leptons, quarks possess color charge, which causes them to engage in the strong interaction. The resulting attraction between different quarks causes the formation of composite particles known as hadrons, there are two families of hadrons, baryons, with three valence quarks, and mesons, with a valence quark and an antiquark. The most common baryons are the proton and the neutron, the blocks of the atomic nucleus. A great number of hadrons are known, most of them differentiated by their quark content, the existence of exotic hadrons with more valence quarks, such as tetraquarks and pentaquarks, has been conjectured but not proven. However, on 13 July 2015, the LHCb collaboration at CERN reported results consistent with pentaquark states, elementary fermions are grouped into three generations, each comprising two leptons and two quarks
21.
Antiquark
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A quark is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation, they can be found only within hadrons, such as baryons and mesons. For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves, Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. There are six types of quarks, known as flavors, up, down, strange, charm, top, up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay, the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions. For every quark flavor there is a type of antiparticle, known as an antiquark. The quark model was proposed by physicists Murray Gell-Mann and George Zweig in 1964. Accelerator experiments have provided evidence for all six flavors, the top quark was the last to be discovered at Fermilab in 1995. The Standard Model is the theoretical framework describing all the known elementary particles. This model contains six flavors of quarks, named up, down, strange, charm, bottom, antiparticles of quarks are called antiquarks, and are denoted by a bar over the symbol for the corresponding quark, such as u for an up antiquark. As with antimatter in general, antiquarks have the mass, mean lifetime, and spin as their respective quarks. Quarks are spin- 1⁄2 particles, implying that they are fermions according to the spin-statistics theorem and they are subject to the Pauli exclusion principle, which states that no two identical fermions can simultaneously occupy the same quantum state. This is in contrast to bosons, any number of which can be in the same state, unlike leptons, quarks possess color charge, which causes them to engage in the strong interaction. The resulting attraction between different quarks causes the formation of composite particles known as hadrons, there are two families of hadrons, baryons, with three valence quarks, and mesons, with a valence quark and an antiquark. The most common baryons are the proton and the neutron, the blocks of the atomic nucleus. A great number of hadrons are known, most of them differentiated by their quark content, the existence of exotic hadrons with more valence quarks, such as tetraquarks and pentaquarks, has been conjectured but not proven. However, on 13 July 2015, the LHCb collaboration at CERN reported results consistent with pentaquark states, elementary fermions are grouped into three generations, each comprising two leptons and two quarks
22.
Meson
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In particle physics, mesons are hadronic subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of quark sub-particles, they have a size, with a diameter of roughly one fermi. All mesons are unstable, with the longest-lived lasting for only a few hundredths of a microsecond, charged mesons decay to form electrons and neutrinos. Uncharged mesons may decay to photons, both of these decays imply that color is no longer a property of the byproducts. Outside of the nucleus, mesons appear in only as short-lived products of very high-energy collisions between particles made of quarks, such as cosmic rays and ordinary matter. Mesons are also frequently produced artificially in particle accelerators in the collisions of protons, anti-protons. Mesons are the associated quantum-field particles that transmit the force between hadrons that pull those together into a nucleus. Higher energy mesons were created momentarily in the Big Bang, but are not thought to play a role in nature today. However, such heavy mesons are regularly created in particle accelerator experiments, mesons are part of the hadron particle family, and are defined simply as particles composed of two quarks. The other members of the family are the baryons, subatomic particles composed of three quarks. Some experiments show evidence of exotic mesons, which do not have the conventional valence quark content of one quark, because quarks have a spin of 1⁄2, the difference in quark-number between mesons and baryons results in conventional two-quark mesons being bosons, whereas baryons are fermions. Each type of meson has a corresponding antiparticle in which quarks are replaced by their corresponding antiquarks and vice versa. For example, a pion is made of one up quark and one down antiquark, and its corresponding antiparticle. Because mesons are composed of quarks, they participate in both the weak and strong interactions, mesons with net electric charge also participate in the electromagnetic interaction. Mesons are classified according to their content, total angular momentum, parity and various other properties. Although no meson is stable, those of mass are nonetheless more stable than the more massive. Mesons are also less massive than baryons, meaning that they are more easily produced in experiments. For example, the quark was first seen in the J/Psi meson in 1974
23.
Hadron
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In particle physics, a hadron /ˈhædrɒn/ is a composite particle made of quarks held together by the strong force in a similar way as molecules are held together by the electromagnetic force. Hadrons are categorized into two families, baryons, made of three quarks, and mesons, made of one quark and one antiquark, protons and neutrons are examples of baryons, pions are an example of a meson. Hadrons containing more than three valence quarks have been discovered in recent years, a tetraquark state, named the Z−, was discovered in 2007 by the Belle Collaboration and confirmed as a resonance in 2014 by the LHCb collaboration. Two pentaquark states, named P+ c and P+ c, were discovered in 2015 by the LHCb collaboration, there are several more exotic hadron candidates, and other colour-singlet quark combinations may also exist. Of the hadrons, protons are stable, and neutrons bound within atomic nuclei are stable, other hadrons are unstable under ordinary conditions, free neutrons decay with a half-life of about 611 seconds. Experimentally, hadron physics is studied by colliding protons or nuclei of elements such as lead. The term hadron was introduced by Lev B, okun in a plenary talk at the 1962 International Conference on High Energy Physics. In this talk he said, Notwithstanding the fact that this report deals with weak interactions and these particles pose not only numerous scientific problems, but also a terminological problem. The point is that strongly interacting particles is a very clumsy term which does not yield itself to the formation of an adjective, for this reason, to take but one instance, decays into strongly interacting particles are called non-leptonic. This definition is not exact because non-leptonic may also signify photonic, in this report I shall call strongly interacting particles hadrons, and the corresponding decays hadronic. I hope that this terminology will prove to be convenient, okun,1962 According to the quark model, the properties of hadrons are primarily determined by their so-called valence quarks. For example, a proton is composed of two up quarks and one down quark, adding these together yields the proton charge of +1. Although quarks also carry color charge, hadrons must have total color charge because of a phenomenon called color confinement. That is, hadrons must be colorless or white and these are the simplest of the two ways, three quarks of different colors, or a quark of one color and an antiquark carrying the corresponding anticolor. Hadrons with the first arrangement are called baryons, and those with the arrangement are mesons. Hadrons, however, are not composed of just three or two quarks, because of the strength of the strong force, more accurately, strong force gluons have enough energy to have resonances composed of massive quarks. Thus, virtual quarks and antiquarks, in a 1,1 ratio, the two or three quarks that compose a hadron are the excess of quarks vs. antiquarks, and so too in the case of anti-hadrons. Massless virtual gluons compose the majority of particles inside hadrons
24.
Mean lifetime
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A quantity is subject to exponential decay if it decreases at a rate proportional to its current value. Symbolically, this process can be expressed by the differential equation. The solution to this equation is, N = N0 e − λ t, where N is the quantity at time t, and N0 = N is the initial quantity, i. e. the quantity at time t =0. If the decaying quantity, N, is the number of elements in a certain set. This is called the lifetime, τ, and it can be shown that it relates to the decay rate, λ, in the following way. For example, if the population of the assembly, N, is 1000. A very similar equation will be seen below, which arises when the base of the exponential is chosen to be 2, in that case the scaling time is the half-life. A more intuitive characteristic of exponential decay for many people is the time required for the quantity to fall to one half of its initial value. This time is called the half-life, and often denoted by the symbol t1/2, the half-life can be written in terms of the decay constant, or the mean lifetime, as, t 1 /2 = ln λ = τ ln . When this expression is inserted for τ in the equation above, and ln 2 is absorbed into the base. Thus, the amount of left is 2−1 = 1/2 raised to the number of half-lives that have passed. Thus, after 3 half-lives there will be 1/23 = 1/8 of the material left. Therefore, the mean lifetime τ is equal to the half-life divided by the log of 2, or. E. g. polonium-210 has a half-life of 138 days, the equation that describes exponential decay is d N d t = − λ N or, by rearranging, d N N = − λ d t. This is the form of the equation that is most commonly used to describe exponential decay, any one of decay constant, mean lifetime, or half-life is sufficient to characterise the decay. The notation λ for the constant is a remnant of the usual notation for an eigenvalue. In this case, λ is the eigenvalue of the negative of the operator with N as the corresponding eigenfunction. The units of the constant are s−1
25.
Muon
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The muon is an elementary particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton, as is the case with other leptons, the muon is not believed to have any sub-structure—that is, it is not thought to be composed of any simpler particles. The muon is a subatomic particle with a mean lifetime of 2.2 µs. Muon decay almost always produces at least three particles, which must include an electron of the charge as the muon and two neutrinos of different types. Like all elementary particles, the muon has a corresponding antiparticle of opposite charge but equal mass and spin, muons are denoted by μ− and antimuons by μ+. Muons were previously called mu mesons, but are not classified as mesons by modern particle physicists, muons have a mass of 105.7 MeV/c2, which is about 207 times that of the electron. Due to their mass, muons are not as sharply accelerated when they encounter electromagnetic fields. As an example, so-called secondary muons, generated by cosmic rays hitting the atmosphere, can penetrate to the Earths surface, because muons have a very large mass and energy compared with the decay energy of radioactivity, they are never produced by radioactive decay. These interactions usually produce pi mesons initially, which most often decay to muons, muons were discovered by Carl D. Anderson and Seth Neddermeyer at Caltech in 1936, while studying cosmic radiation. Anderson noticed particles that curved differently from electrons and other known particles when passed through a magnetic field and they were negatively charged but curved less sharply than electrons, but more sharply than protons, for particles of the same velocity. Thus Anderson initially called the new particle a mesotron, adopting the prefix meso- from the Greek word for mid-, the existence of the muon was confirmed in 1937 by J. C. The transition of a particle from neutron state to proton state is not always accompanied by the emission of light particles. The transition is taken up by another heavy particle. Because of its mass, the mu meson was initially thought to be Yukawas particle, with two particles now known with the intermediate mass, the more general term meson was adopted to refer to any such particle within the correct mass range between electrons and nucleons. The difference, in part, was that mu mesons did not interact with the nuclear force, newer mesons also showed evidence of behaving like the pi meson in nuclear interactions, but not like the mu meson. Also, the mu mesons decay products included both a neutrino and an antineutrino, rather than just one or the other, as was observed in the decay of other charged mesons. In the quark model, a meson was no longer defined by mass, mu mesons, however, had shown themselves to be fundamental particles like electrons, with no quark structure. Thus, mu mesons were not mesons at all, in the new sense and use of the term used with the quark model of particle structure
26.
Gamma ray
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Gamma ray, denoted by the lower-case Greek letter gamma, is penetrating electromagnetic radiation of a kind arising from the radioactive decay of atomic nuclei. It consists of photons in the highest observed range of photon energy, paul Villard, a French chemist and physicist, discovered gamma radiation in 1900 while studying radiation emitted by radium. In 1903, Ernest Rutherford named this radiation gamma rays, Rutherford had previously discovered two other types of radioactive decay, which he named alpha and beta rays. Gamma rays are able to ionize atoms, and are thus biologically hazardous. The decay of a nucleus from a high energy state to a lower energy state. Natural sources of gamma rays on Earth are observed in the decay of radionuclides. There are rare terrestrial natural sources, such as lightning strikes and terrestrial gamma-ray flashes, However, a large fraction of such astronomical gamma rays are screened by Earths atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz, and therefore have energies above 100 keV and wavelengths less than 10 picometers, However, this is not a strict definition, but rather only a rule-of-thumb description for natural processes. Electromagnetic radiation from radioactive decay of nuclei is referred to as gamma rays no matter its energy. This radiation commonly has energy of a few hundred keV, in astronomy, gamma rays are defined by their energy, and no production process needs to be specified. The energies of gamma rays from astronomical sources range to over 10 TeV, a notable example is the extremely powerful bursts of high-energy radiation referred to as long duration gamma-ray bursts, of energies higher than can be produced by radioactive decay. These bursts of gamma rays are thought to be due to the collapse of stars called hypernovae, the first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, a nucleus emits a gamma ray almost immediately upon formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, However, Villard did not consider naming them as a different fundamental type. Rutherford also noted that gamma rays were not deflected by a field, another property making them unlike alpha. Gamma rays were first thought to be particles with mass, like alpha, Rutherford initially believed that they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated that they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays, but with shorter wavelengths and higher frequency. This was eventually recognized as giving them more energy per photon
27.
Omega meson
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This list is of all known and predicted scalar, pseudoscalar and vector mesons. See list of particles for a detailed list of particles found in particle physics. Mesons are unstable subatomic particles composed of one quark and one antiquark and they are part of the hadron particle family – particles made of quarks. The other members of the family are the baryons – subatomic particles composed of three quarks. The main difference between mesons and baryons is that mesons have integer spin while baryons are fermions, because mesons are bosons, the Pauli exclusion principle does not apply to them. Because of this, they can act as force mediating particles on short distances, since mesons are composed of quarks, they participate in both the weak and strong interactions. Mesons with net electric charge also participate in the electromagnetic interaction and they are classified according to their quark content, total angular momentum, parity, and various other properties such as C-parity and G-parity. While no meson is stable, those of mass are nonetheless more stable than the most massive mesons. They are also less massive than baryons, meaning that they are more easily produced in experiments. For example, the quark was first seen in the J/Psi meson in 1974. Each meson has a corresponding antiparticle where quarks are replaced by their corresponding antiquarks, for example, a positive pion is made of one up quark and one down antiquark, and its corresponding antiparticle, the negative pion, is made of one up antiquark and one down quark. The symbols encountered in these lists are, I, J, P, C, G, u, d, s, c, b, Q, B, S, C, the following lists detail all known and predicted pseudoscalar and vector mesons. The properties and quark content of the particles are tabulated below, for the corresponding antiparticles, simply change quarks into antiquarks and flip the sign of Q, B, S, C, and B′. Particles with † next to their names have been predicted by the standard model, values in red have not been firmly established by experiments, but are predicted by the quark model and are consistent with the measurements. ^ Makeup inexact due to non-zero quark masses, ^ PDG reports the resonance width. Here the conversion τ = ħ⁄Γ is given instead, no definite lifetime ^ The mass of the K0 L and K0 S are given as that of the K0. However, it is known that a difference between the masses of the K0 L and K0 S on the order of 2. 2×10−11 MeV/c2 exists, Makeup is missing small CP–violating term. ^ PDG reports the resonance width, here the conversion τ = ħ⁄Γ is given instead
28.
Nuclear force
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The nuclear force is a force that acts between the protons and neutrons of atoms. Neutrons and protons, both nucleons, are affected by the force almost identically. The nuclear force binds nucleons into atomic nuclei, the nuclear force is powerfully attractive between nucleons at distances of about 1 femtometer, but it rapidly decreases to insignificance at distances beyond about 2.5 fm. At distances less than 0.7 fm, the force becomes repulsive. This repulsive component is responsible for the size of nuclei. By comparison, the size of an atom, measured in angstroms, is five orders of magnitude larger. The nuclear force is not simple, however, since it depends on the spins, has a tensor component. The nuclear force is not one of the forces of nature. The nuclear force plays an role in storing energy that is used in nuclear power. Work is required to bring charged protons together against their electric repulsion and this energy is stored when the protons and neutrons are bound together by the nuclear force to form a nucleus. The mass of a nucleus is less than the sum total of the masses of the protons and neutrons. The difference in masses is known as the defect, which can be expressed as an energy equivalent. Energy is released when a heavy nucleus breaks apart into two or more lighter nuclei and this energy is the electromagnetic potential energy that is released when the nuclear force no longer holds the charged nuclear fragments together. A quantitative description of the nuclear force relies on equations that are partly empirical and these equations model the internucleon potential energies, or potentials. The constants for the equations are phenomenological, that is, determined by fitting the equations to experimental data, the internucleon potentials attempt to describe the properties of nucleon–nucleon interaction. Once determined, any potential can be used in, e. g. the Schrödinger equation to determine the quantum mechanical properties of the nucleon system. The discovery of the neutron in 1932 revealed that atomic nuclei were made of protons and neutrons, by 1935 the nuclear force was conceived to be transmitted by particles called mesons. This theoretical development included a description of the Yukawa potential, an example of a nuclear potential
29.
Nucleon
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In chemistry and physics, nucleons are the proton and the neutron, which are the constituents of the atomic nucleus, and are themselves composed of down and up quarks. The number of nucleons defines an isotopes mass number, the atom is made up of a nucleus surrounded by electrons. Until the 1960s, nucleons were thought to be elementary particles, now they are known to be composite particles, made of three quarks bound together by the so-called strong interaction. The interaction between two or more nucleons is called internucleon interactions or nuclear force, which is ultimately caused by the strong interaction. Nucleons sit at the boundary where particle physics and nuclear physics overlap, Particle physics, particularly quantum chromodynamics, provides the fundamental equations that explain the properties of quarks and of the strong interaction. These equations explain quantitatively how quarks can bind together into protons and neutrons, however, when multiple nucleons are assembled into an atomic nucleus, these fundamental equations become too difficult to solve directly. Instead, nuclides are studied within nuclear physics, which studies nucleons and their interactions by approximations and models and these models can successfully explain nuclide properties, for example, whether or not a certain nuclide undergoes radioactive decay. The proton and neutron are both baryons and both fermions, one carries a positive net charge and the other carries a zero net charge, the protons mass is only 0. 1% less than the neutrons. Thus, they can be viewed as two states of the nucleon, and together form an isospin doublet. In isospin space, neutrons can be transformed into protons via SU symmetries and these nucleons are acted upon equally by the strong interaction, which is invariant under rotation in isospin space. According to the Noether theorem, isospin is conserved with respect to the strong interaction, protons and neutrons are most important and best known for constituting atomic nuclei, but they can also be found on their own, not part of a larger nucleus. A proton on its own is the nucleus of the hydrogen-1 atom, a neutron on its own is unstable, but they can be found in nuclear reactions and are used in scientific analysis. Both the proton and neutron are made of three quarks, the proton is made of two up quarks and one down quark, while the neutron is one up quark and two down quarks. The quarks are held together by the force, or equivalently, by gluons. An up quark has electric charge + 2⁄3 e, and a down quark has charge − 1⁄3 e, so the electric charge of the proton and neutron are +e and 0. The word neutron comes from the fact that it is electrically neutral, the mass of the proton and neutron is quite similar, The proton is 1. 6726×10−27 kg or 938.27 MeV/c2, while the neutron is 1. 6749×10−27 kg or 939.57 MeV/c2. The neutron is roughly 0. 1% heavier, the similarity in mass can be explained roughly by the slight difference in mass of up quark and down quark composing the nucleons. However, detailed explanation remains a problem in particle physics
30.
Radioactive decay
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A material containing such unstable nuclei is considered radioactive. Certain highly excited short-lived nuclear states can decay through neutron emission, or more rarely, however, for a collection of atoms, the collections expected decay rate is characterized in terms of their measured decay constants or half-lives. This is the basis of radiometric dating, the half-lives of radioactive atoms have no known upper limit, spanning a time range of over 55 orders of magnitude, from nearly instantaneous to far longer than the age of the universe. A radioactive nucleus with spin can have no defined orientation. If there are multiple particles produced during a single decay, as in decay, their relative angular distribution. Such a parent process could be a previous decay, or a nuclear reaction, the decaying nucleus is called the parent radionuclide, and the process produces at least one daughter nuclide. Except for gamma decay or internal conversion from an excited state. When the number of changes, an atom of a different chemical element is created. The first decay processes to be discovered were alpha decay, beta decay, alpha decay occurs when the nucleus ejects an alpha particle. This is the most common process of emitting nucleons, but highly excited nuclei can eject single nucleons, or in the case of cluster decay, specific light nuclei of other elements. Beta decay occurs when the nucleus emits an electron or positron, the nucleus may capture an orbiting electron, causing a proton to convert into a neutron in a process called electron capture. All of these result in a well-defined nuclear transmutation. By contrast, there are radioactive decay processes that do not result in a nuclear transmutation, another type of radioactive decay results in products that vary, appearing as two or more fragments of the original nucleus with a range of possible masses. For a summary table showing the number of stable and radioactive nuclides in each category, there are 29 naturally occurring chemical elements on Earth that are radioactive. They are those that contain 34 radionuclides that date before the time of formation of the solar system, well-known examples are uranium and thorium, but also included are naturally occurring long-lived radioisotopes, such as potassium-40. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel and these materials glow in the dark after exposure to light, and he suspected that the glow produced in cathode ray tubes by X-rays might be associated with phosphorescence. He wrapped a photographic plate in black paper and placed various phosphorescent salts on it, all results were negative until he used uranium salts. The uranium salts caused a blackening of the plate in spite of the plate being wrapped in black paper and these radiations were given the name Becquerel Rays
31.
Cosmic ray
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Cosmic rays are high-energy radiation, mainly originating outside the Solar System. Upon impact with the Earths atmosphere, cosmic rays can produce showers of particles that sometimes reach the surface. Composed primarily of protons and atomic nuclei, they are of mysterious origin. Data from the Fermi space telescope have been interpreted as evidence that a significant fraction of cosmic rays originate from the supernovae explosions of stars. Active galactic nuclei probably also produce cosmic rays, the term ray is a historical accident, as cosmic rays were at first, and wrongly, thought to be mostly electromagnetic radiation. In current usage, the cosmic ray almost exclusively refers to massive particles. Massive particles – those that have rest mass – can gain additional, kinetic, mass-energy when they are moving, through this process, some particles acquire tremendously high mass-energies. These are significantly higher than the energy of even the highest-energy photons detected to date. The energy of the massless photon depends solely on frequency, not speed, at the higher end of the energy spectrum, relativistic kinetic energy is the main source of the mass-energy of cosmic rays. Hence, the highest-energy detected fermionic cosmic ray was around 3×106 times more energetic than the highest-energy detected cosmic photons, of primary cosmic rays, which originate outside of Earths atmosphere, about 99% are the nuclei of well-known atoms, and about 1% are solitary electrons. Of the nuclei, about 90% are simple protons, i. e. hydrogen nuclei, 9% are alpha particles, identical to helium nuclei, a very small fraction are stable particles of antimatter, such as positrons or antiprotons. The precise nature of this fraction is an area of active research. An active search from Earth orbit for anti-alpha particles has failed to detect them, one can show that such enormous energies might be achieved by means of the Centrifugal mechanism of acceleration in Active galactic nuclei. At 50 J, the highest-energy ultra-high-energy cosmic rays have energies comparable to the energy of a 90-kilometre-per-hour baseball. As a result of discoveries, there has been interest in investigating cosmic rays of even greater energies. Most cosmic rays, however, do not have such extreme energies, however, his paper published in Physikalische Zeitschrift was not widely accepted. In 1911 Domenico Pacini observed simultaneous variations of the rate of ionization over a lake, over the sea, Pacini concluded from the decrease of radioactivity underwater that a certain part of the ionization must be due to sources other than the radioactivity of the Earth. In 1912, Victor Hess carried three enhanced-accuracy Wulf electrometers to an altitude of 5300 meters in a balloon flight
32.
Supernova remnant
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A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by a shock wave, and consists of ejected material expanding from the explosion. In either case, the supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light. These ejecta are highly supersonic, assuming a typical temperature of the medium of 10,000 K. Therefore, a shock wave forms ahead of the ejecta. One of the best observed young supernova remnants was formed by SN 1987A, the youngest known remnant in our galaxy is G1. 9+0.3, discovered in the galactic center. An SNR passes through the stages as it expands, Free expansion of the ejecta. This can last tens to a few hundred years depending on the density of the surrounding gas, sweeping up of a shell of shocked circumstellar and interstellar gas. This begins the Sedov-Taylor phase, which can be modeled by a self-similar analytic solution. Strong X-ray emission traces the strong waves and hot shocked gas. Cooling of the shell, to form a thin, dense shell surrounding the hot interior and this is the pressure-driven snowplow phase. The shell can be seen in optical emission from recombining ionized hydrogen. The dense shell continues to expand from its own momentum and this stage is best seen in the radio emission from neutral hydrogen atoms. Merging with the interstellar medium. There are three types of supernova remnant, Shell-like, such as Cassiopeia A Composite, in which a shell contains a central pulsar wind nebula, mixed-morphology remnants, in which central thermal X-ray emission is seen, enclosed by a radio shell. The thermal X-rays are primarily from swept-up interstellar material, rather than supernova ejecta, examples of this class include the SNRs W28 and W44. Supernova remnants are considered the source of galactic cosmic rays. The connection between cosmic rays and supernovas was first suggested by Walter Baade and Fritz Zwicky in 1934 and this hypothesis is supported by a specific mechanism called shock wave acceleration based on Enrico Fermis ideas, which is still under development
33.
Strong force
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At the range of 10−15 m, the strong force is approximately 137 times as strong as electromagnetism, a million times as strong as the weak interaction and 1038 times as strong as gravitation. The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as proton and neutron, in addition, the strong force binds neutrons and protons to create atomic nuclei. Most of the mass of a proton or neutron is the result of the strong force field energy. The strong interaction is observable at two ranges, on a scale, it is the force that binds protons and neutrons together to form the nucleus of an atom. On the smaller scale, it is the force that holds together to form protons, neutrons. In the latter context, it is known as the color force. The strong force inherently has such a strength that hadrons bound by the strong force can produce new massive particles. Thus, if hadrons are struck by particles, they give rise to new hadrons instead of emitting freely moving radiation. This property of the force is called color confinement, and it prevents the free emission of the strong force, instead, in practice. In the context of binding protons and neutrons together to form atomic nuclei, in this case, it is the residuum of the strong interaction between the quarks that make up the protons and neutrons. As such, the strong interaction obeys a quite different distance-dependent behavior between nucleons, from when it is acting to bind quarks within nucleons. The binding energy that is released on the breakup of a nucleus is related to the residual strong force and is harnessed as fission energy in nuclear power. The strong interaction is mediated by the exchange of particles called gluons that act between quarks, antiquarks, and other gluons. Gluons are thought to interact with quarks and other gluons by way of a type of charge called color charge. Color charge is analogous to electromagnetic charge, but it comes in three rather than one, which results in a different type of force, with different rules of behavior. These rules are detailed in the theory of quantum chromodynamics, which is the theory of quark-gluon interactions, after the Big Bang and during the electroweak epoch of the universe, the electroweak force separated from the strong force. A Grand Unified Theory is hypothesized to exist to describe this, but no theory has yet been successfully formulated. Before the 1970s, physicists were uncertain as to how the nucleus was bound together
34.
Gluon
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In lay terms, they glue quarks together, forming protons and neutrons. In technical terms, gluons are vector gauge bosons that mediate interactions of quarks in quantum chromodynamics. Gluons themselves carry the charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction, gluons therefore participate in the strong interaction in addition to mediating it, making QCD significantly harder to analyze than QED. The gluon is a boson, like the photon, it has a spin of 1. In quantum field theory, unbroken gauge invariance requires that gauge bosons have zero mass, the gluon has negative intrinsic parity. Unlike the single photon of QED or the three W and Z bosons of the interaction, there are eight independent types of gluon in QCD. This may be difficult to understand intuitively, quarks carry three types of color charge, antiquarks carry three types of anticolor. Gluons may be thought of as carrying both color and anticolor, but to understand how they are combined, it is necessary to consider the mathematics of color charge in more detail. A relevant illustration in the case at hand would be a gluon with a state described by. This is read as red–antiblue plus blue–antired, the color singlet state is, /3. In words, if one could measure the color of the state, there would be equal probabilities of it being red-antired, blue-antiblue, there are eight remaining independent color states, which correspond to the eight types or eight colors of gluons. Because states can be mixed together as discussed above, there are ways of presenting these states. One commonly used list is, These are equivalent to the Gell-Mann matrices, there are many other possible choices, but all are mathematically equivalent, at least equally complex, and give the same physical results. Technically, QCD is a theory with SU gauge symmetry. Quarks are introduced as spinors in Nf flavors, each in the representation of the color gauge group. The gluons are vectors in the adjoint representation of color SU, for a general gauge group, the number of force-carriers is always equal to the dimension of the adjoint representation. For the simple case of SU, the dimension of this representation is N2 −1, in terms of group theory, the assertion that there are no color singlet gluons is simply the statement that quantum chromodynamics has an SU rather than a U symmetry
35.
Strong nuclear force
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The nuclear force is a force that acts between the protons and neutrons of atoms. Neutrons and protons, both nucleons, are affected by the force almost identically. The nuclear force binds nucleons into atomic nuclei, the nuclear force is powerfully attractive between nucleons at distances of about 1 femtometer, but it rapidly decreases to insignificance at distances beyond about 2.5 fm. At distances less than 0.7 fm, the force becomes repulsive. This repulsive component is responsible for the size of nuclei. By comparison, the size of an atom, measured in angstroms, is five orders of magnitude larger. The nuclear force is not simple, however, since it depends on the spins, has a tensor component. The nuclear force is not one of the forces of nature. The nuclear force plays an role in storing energy that is used in nuclear power. Work is required to bring charged protons together against their electric repulsion and this energy is stored when the protons and neutrons are bound together by the nuclear force to form a nucleus. The mass of a nucleus is less than the sum total of the masses of the protons and neutrons. The difference in masses is known as the defect, which can be expressed as an energy equivalent. Energy is released when a heavy nucleus breaks apart into two or more lighter nuclei and this energy is the electromagnetic potential energy that is released when the nuclear force no longer holds the charged nuclear fragments together. A quantitative description of the nuclear force relies on equations that are partly empirical and these equations model the internucleon potential energies, or potentials. The constants for the equations are phenomenological, that is, determined by fitting the equations to experimental data, the internucleon potentials attempt to describe the properties of nucleon–nucleon interaction. Once determined, any potential can be used in, e. g. the Schrödinger equation to determine the quantum mechanical properties of the nucleon system. The discovery of the neutron in 1932 revealed that atomic nuclei were made of protons and neutrons, by 1935 the nuclear force was conceived to be transmitted by particles called mesons. This theoretical development included a description of the Yukawa potential, an example of a nuclear potential
36.
Atomic nucleus
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After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg. Almost all of the mass of an atom is located in the nucleus, protons and neutrons are bound together to form a nucleus by the nuclear force. The diameter of the nucleus is in the range of 6985175000000000000♠1.75 fm for hydrogen to about 6986150000000000000♠15 fm for the heaviest atoms and these dimensions are much smaller than the diameter of the atom itself, by a factor of about 23,000 to about 145,000. The branch of physics concerned with the study and understanding of the nucleus, including its composition. The nucleus was discovered in 1911, as a result of Ernest Rutherfords efforts to test Thomsons plum pudding model of the atom, the electron had already been discovered earlier by J. J. Knowing that atoms are electrically neutral, Thomson postulated that there must be a charge as well. In his plum pudding model, Thomson suggested that an atom consisted of negative electrons randomly scattered within a sphere of positive charge, to his surprise, many of the particles were deflected at very large angles. This justified the idea of an atom with a dense center of positive charge. The term nucleus is from the Latin word nucleus, a diminutive of nux, in 1844, Michael Faraday used the term to refer to the central point of an atom. The modern atomic meaning was proposed by Ernest Rutherford in 1912, the adoption of the term nucleus to atomic theory, however, was not immediate. In 1916, for example, Gilbert N, the nuclear strong force extends far enough from each baryon so as to bind the neutrons and protons together against the repulsive electrical force between the positively charged protons. The nuclear strong force has a short range, and essentially drops to zero just beyond the edge of the nucleus. The collective action of the charged nucleus is to hold the electrically negative charged electrons in their orbits about the nucleus. The collection of negatively charged electrons orbiting the nucleus display an affinity for certain configurations, which chemical element an atom represents is determined by the number of protons in the nucleus, the neutral atom will have an equal number of electrons orbiting that nucleus. Individual chemical elements can create more stable electron configurations by combining to share their electrons and it is that sharing of electrons to create stable electronic orbits about the nucleus that appears to us as the chemistry of our macro world. Protons define the entire charge of a nucleus, and hence its chemical identity, neutrons are electrically neutral, but contribute to the mass of a nucleus to nearly the same extent as the protons. Neutrons explain the phenomenon of isotopes – varieties of the chemical element which differ only in their atomic mass. They are sometimes viewed as two different quantum states of the particle, the nucleon
37.
Lepton
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A lepton is an elementary, half-integer spin particle that does not undergo strong interactions. Two main classes of leptons exist, charged leptons, and neutral leptons, the best known of all leptons is the electron. There are six types of leptons, known as flavours, forming three generations, electrons have the least mass of all the charged leptons. The heavier muons and taus will rapidly change into electrons and neutrinos through a process of particle decay, thus electrons are stable and the most common charged lepton in the universe, whereas muons and taus can only be produced in high energy collisions. Leptons have various properties, including electric charge, spin. Unlike quarks however, leptons are not subject to the strong interaction, for every lepton flavor there is a corresponding type of antiparticle, known as an antilepton, that differs from the lepton only in that some of its properties have equal magnitude but opposite sign. However, according to theories, neutrinos may be their own antiparticle. The first charged lepton, the electron, was theorized in the century by several scientists and was discovered in 1897 by J. J. Thomson. The next lepton to be observed was the muon, discovered by Carl D. Anderson in 1936, after investigation, it was realized that the muon did not have the expected properties of a meson, but rather behaved like an electron, only with higher mass. It took until 1947 for the concept of leptons as a family of particle to be proposed, the first neutrino, the electron neutrino, was proposed by Wolfgang Pauli in 1930 to explain certain characteristics of beta decay. It was first observed in the Cowan–Reines neutrino experiment conducted by Clyde Cowan, the muon neutrino was discovered in 1962 by Leon M. The tau neutrino remained elusive until July 2000, when the DONUT collaboration from Fermilab announced its discovery, Leptons are an important part of the Standard Model. Electrons are one of the components of atoms, alongside protons and neutrons, exotic atoms with muons and taus instead of electrons can also be synthesized, as well as lepton–antilepton particles such as positronium. The name lepton comes from the Greek λεπτός leptós, fine, small, thin, Lepton was first used by physicist Léon Rosenfeld in 1948, Following a suggestion of Prof. C. Møller, I adopt—as a pendant to nucleon—the denomination lepton to denote a particle of small mass, the etymology incorrectly implies that all the leptons are of small mass. However, the mass of the tau is nearly twice that of the proton, the first lepton identified was the electron, discovered by J. J. Thomson and his team of British physicists in 1897, then in 1930 Wolfgang Pauli postulated the electron neutrino to preserve conservation of energy, conservation of momentum, and conservation of angular momentum in beta decay. Pauli theorized that a particle was carrying away the difference between the energy, momentum, and angular momentum of the initial and observed final particles
38.
University of Bristol
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The University of Bristol is a red brick research university located in Bristol, United Kingdom. It received its charter in 1909, and its predecessor institution, University College. Bristol is organised into six academic faculties composed of multiple schools, the university had a total income of £565.8 million in 2015/16, of which £146.2 million was from research grants and contracts. It is the largest independent employer in Bristol, the University of Bristol is ranked 11th in the UK for its research, according to the Research Excellence Framework 2014 by GPA. The University of Bristol is ranked 37th by the QS World University Rankings 2015-16, and is ranked amongst the top of UK universities by QS, THE, a highly selective institution, it has an average of 6.4 to 13.1 applicants for each undergraduate place. Current academics include 21 fellows of the Academy of Medical Sciences,13 fellows of the British Academy,13 fellows of the Royal Academy of Engineering and 44 fellows of the Royal Society. In addition, the university holds an Erasmus Charter, sending more than 500 students per year to partner institutions in Europe, the earliest antecedent of the university was the engineering department of the Merchant Venturers Technical College which became the engineering faculty of Bristol University. The university was preceded by Bristol Medical School and University College, Bristol, founded in 1876. The university was able to apply for a royal charter due to the support of the Wills and Fry families. The Wills Family made a vast fortune from the tobacco industry, the royal charter was gained in May 1909, with 288 undergraduates and 400 other students entering the university in October 1909. Henry Overton Wills III became its first chancellor, the University College was the first such institution in the country to admit women on the same basis as men. However, women were forbidden to take examinations in medicine until 1906, Bristol does not have a campus but is spread over a considerable geographic area. Most of its activities, however, are concentrated in the area of the city centre and it is a member of the Russell Group of research-led UK universities, the Coimbra Group of leading European universities and the Worldwide Universities Network. After the founding of the University College in 1876, Government support began in 1889, in December 1909, the King granted such a charter and erected the University of Bristol. Henry Wills became its first chancellor and Conwy Lloyd Morgan the first vice-chancellor, Wills died in 1911 and in tribute his sons George and Harry built the Wills Memorial Building, starting in 1913 and finally finishing in 1925. Today, it parts of the academic provision for earth sciences and law. The Wills Memorial Building is a Grade II* listed building, in 1920, George Wills bought the Victoria Rooms and endowed them to the university as a Students Union. The building now houses the Department of Music and is a Grade II* listed building, at the point of foundation, the university was required to provide for the local community
39.
Particle accelerator
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A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to nearly light speed and to contain them in well-defined beams. Large accelerators are used in physics as colliders, or as synchrotron light sources for the study of condensed matter physics. There are currently more than 30,000 accelerators in operation around the world, there are two basic classes of accelerators, electrostatic and electrodynamic accelerators. Electrostatic accelerators use electric fields to accelerate particles. The most common types are the Cockcroft–Walton generator and the Van de Graaff generator, a small-scale example of this class is the cathode ray tube in an ordinary old television set. The achievable kinetic energy for particles in these devices is determined by the accelerating voltage, electrodynamic or electromagnetic accelerators, on the other hand, use changing electromagnetic fields to accelerate particles. Since in these types the particles can pass through the accelerating field multiple times. This class, which was first developed in the 1920s, is the basis for most modern large-scale accelerators, because colliders can give evidence of the structure of the subatomic world, accelerators were commonly referred to as atom smashers in the 20th century. Despite the fact that most accelerators actually propel subatomic particles, the term persists in popular usage when referring to particle accelerators in general. Beams of high-energy particles are useful for both fundamental and applied research in the sciences, and also in many technical and industrial fields unrelated to fundamental research and it has been estimated that there are approximately 30,000 accelerators worldwide. The bar graph shows the breakdown of the number of industrial accelerators according to their applications, for the most basic inquiries into the dynamics and structure of matter, space, and time, physicists seek the simplest kinds of interactions at the highest possible energies. These typically entail particle energies of many GeV, and the interactions of the simplest kinds of particles, leptons and quarks for the matter, the largest and highest energy particle accelerator used for elementary particle physics is the Large Hadron Collider at CERN, operating since 2009. These investigations often involve collisions of heavy nuclei – of atoms like iron or gold – at energies of several GeV per nucleon, the largest such particle accelerator is the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. An example of type of machine is LANSCE at Los Alamos. A large number of light sources exist worldwide. The ESRF in Grenoble, France has been used to extract detailed 3-dimensional images of trapped in amber. Thus there is a demand for electron accelerators of moderate energy. Everyday examples of particle accelerators are cathode ray tubes found in television sets and these low-energy accelerators use a single pair of electrodes with a DC voltage of a few thousand volts between them
40.
Pic du Midi de Bigorre
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The Pic du Midi de Bigorre or simply the Pic du Midi is a mountain in the French Pyrenees famous for its Pic du Midi Observatory. The Pic du Midi Observatory is an observatory located at 2877 meters on top of the Pic du Midi de Bigorre mountain in the French Pyrenees. The 8 metre dome was completed in 1908, under the direction of Benjamin Baillaud. It housed a powerful mechanical equatorial reflector which was used in 1909 to formally discredit the Martian canal theory, in 1946 Mr. Gentilli funded a dome and a 0. 60-meter telescope, and in 1958, a spectrograph was installed. A1. 06-meter telescope was installed in 1963, funded by NASA and was used to take detailed photographs of the surface of the Moon in preparation for the Apollo missions, the results showed atmospheres in chemical equilibrium. It is the largest telescope in France, the observatory also has a coronagraph, which is used to study the solar corona. A0. 60-meter telescope is located at the top of Pic du Midi. Since 1982 this T60 is dedicated to astronomy and managed by a group of amateurs. There are currently at the top, The 0. 55-meter telescope, The 0. 60-meter telescope, the observatory is located at 42°56′N 0°8′E, placing it very close to the Greenwich meridian. The observatory was featured in the video game Rainbow Six, Vegas 2 under a different name, the observatory in-game is said to be located on the fictional Pic des Pyrenees. Saturns moon Helene, was discovered by French astronomers Pierre Laques and Jean Lecacheux in 1980 from ground-based observations at this observatory and it is also a trojan moon of Dione
41.
Pyrenees
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The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain. For the most part, the main crest forms a divide between France and Spain, with the microstate of Andorra sandwiched in between. The Crown of Aragon and the Kingdom of Navarre have historically extended on both sides of the range, with smaller northern portions now in France and larger southern parts now in Spain. The demonym for the noun Pyrenees in English is Pyrenean, in Greek mythology, Pyrene is a princess who gave her name to the Pyrenees. The Greek historian Herodotus says Pyrene is the name of a town in Celtic Europe, Hercules, characteristically drunk and lustful, violates the sacred code of hospitality and rapes his hosts daughter. Pyrene gives birth to a serpent and runs away to the woods, alone, she pours out her story to the trees, attracting the attention of wild beasts who tear her to pieces. After his victory over Geryon, Hercules passes through the kingdom of Bebryx again, and all the rock-cliffs and wild-beast haunts echo back Pyrene. … The mountains hold on to the name through the ages. Pliny the Elder connects the story of Hercules and Pyrene to Lusitania, the Spanish Pyrenees are part of the following provinces, from east to west, Girona, Barcelona, Lleida, Huesca, Navarra and Gipuzkoa. The French Pyrenees are part of the following départements, from east to west, Pyrénées-Orientales, Aude, Ariège, Haute-Garonne, Hautes-Pyrénées, the independent principality of Andorra is sandwiched in the eastern portion of the mountain range between the Spanish Pyrenees and French Pyrenees. Physiographically, the Pyrenees may be divided into three sections, the Atlantic, the Central, and the Eastern Pyrenees, together, they form a distinct physiographic province of the larger Alpine System division. In the Western Pyrenees, from the Basque mountains near the Bay of Biscay of the Atlantic Ocean, at the eastern end on the southern side lies a distinct area known as the Sub-Pyrenees. On the French side the slopes of the range descend abruptly. The Pyrenees are older than the Alps, their sediments were first deposited in coastal basins during the Paleozoic and Mesozoic eras, the intense pressure and uplifting of the Earths crust first affected the eastern part and moved progressively to the entire chain, culminating in the Eocene Epoch. The eastern part of the Pyrenees consists largely of granite and gneissose rocks, the massive and unworn character of the chain comes from its abundance of granite, which is particularly resistant to erosion, as well as weak glacial development. Low passes are lacking, and the roads and the railroads between France and Spain run only in the lowlands at the western and eastern ends of the Pyrenees. A notable visual feature of mountain range is La Brèche de Roland, a gap in the ridge line. Coal deposits capable of being profitably worked are situated chiefly on the Spanish slopes, the open pit of Trimoun close to the commune of Luzenac is one of the greatest sources of talc in Europe
42.
Chacaltaya
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Chacaltaya is a mountain in the Cordillera Real, one of the mountain ranges of the Cordillera Oriental, itself a range of the Bolivian Andes. Chacaltayas glacier — which was as old as 18,000 years — had an area of 0.22 km2 in 1940, half of the meltdown, as measured by volume, took place before 1980. The final meltdown after 1980, due to missing precipitation and the phase of El Niño. The glacier was formerly one of the highest in South America, located about 30 kilometers from La Paz, the glacier on Chacaltaya served as Bolivias only ski resort. It was the worlds highest lift-served ski area and the northernmost in South America as well as the second most equatorial after Maoke. The road to the base of the 200-meter drop is reached by a narrow road, traditionally, due to the extreme cold weather, the lift operated exclusively on weekends from November to March. Since 2009, skiing is restricted to a 600-foot stretch that sometimes receives sufficient snowfall for a run during the winter, the mountain is also popular with amateur mountaineers, as the aforementioned road stops only 200 metres from the summit. Scientists at the Mount Chacaltaya Laboratory started measuring the Chacaltaya glacier in the 1990s, predicted at that time to survive until 2015, the Chacaltaya glacier has melted at a much faster rate than expected. The 18, 000-year-old glacier has been reduced in recent years to just a few patches of ice. Many Bolivians on the Altiplano and in two of Bolivias main cities — La Paz and El Alto — partially depend on the melting of Andean glaciers for their water supply during the dry season. The World Bank has warned that many glaciers in the portion of the Andes are expected to disappear within 20 years. This will threaten the water supplies of nearly 80 million people as well as the generation of hydropower. Bolivia, Ecuador and Peru depend on hydropower for about half their electricity, located at 5,240 meters, the Mount Chacaltaya Laboratory began as a weather station in 1942. It is an important site for gamma ray research since it gained notoriety in the 1940s due to the first observations of pions, the Chacaltaya Observatory belongs to the Universidad Mayor de San Andrés and it is operated in collaboration with other universities worldwide. It currently hosts the Cosmic Rays research group and since 2011 the Chacaltaya GAW station, the Chacaltaya GAW station is one of the few monitoring sites of essential climate variables in the Southern Hemisphere. It contributes to the Global Atmosphere Watch program
. doi:10.1126/science.1231160.
