1.
Sensor
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A sensor is always used with other electronics, whether as simple as a light or as complex as a computer. Moreover, analog sensors such as potentiometers and force-sensing resistors are still widely used, applications include manufacturing and machinery, airplanes and aerospace, cars, medicine, robotics and many other aspects of our day-to-day life. A sensors sensitivity indicates how much the output changes when the input quantity being measured changes. For instance, if the mercury in a thermometer moves 1 cm when the changes by 1 °C. Some sensors can also affect what they measure, for instance, Sensors are usually designed to have a small effect on what is measured, making the sensor smaller often improves this and may introduce other advantages. Technological progress allows more and more sensors to be manufactured on a scale as microsensors using MEMS technology. In most cases, a microsensor reaches a higher speed. Most sensors have a transfer function. The sensitivity is defined as the ratio between the output signal and measured property. For example, if a sensor measures temperature and has a voltage output, the sensitivity is the slope of the transfer function. Converting the sensors electrical output to the measured units requires dividing the output by the slope. In addition, an offset is added or subtracted. For example -40 must be added to the output if 0 V output corresponds to -40 C input, for an analog sensor signal to be processed, or used in digital equipment, it needs to be converted to a digital signal, using an analog-to-digital converter. The full scale range defines the maximum and minimum values of the measured property, the sensitivity may in practice differ from the value specified. This is called a sensitivity error and this is an error in the slope of a linear transfer function. If the output differs from the correct value by a constant. This is an error in the y-intercept of a transfer function. Nonlinearity is deviation of a transfer function from a straight line transfer function
2.
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
3.
Experiment
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An experiment is a procedure carried out to support, refute, or validate a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated, experiments vary greatly in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There also exists natural experimental studies, a child may carry out basic experiments to understand gravity, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of activities are very important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, experiments can vary from personal and informal natural comparisons, to highly controlled. Uses of experiments vary considerably between the natural and human sciences, experiments typically include controls, which are designed to minimize the effects of variables other than the single independent variable. This increases the reliability of the results, often through a comparison between control measurements and the other measurements, scientific controls are a part of the scientific method. Ideally, all variables in an experiment are controlled and none are uncontrolled, in such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, and that results are due to the effect of the tested variable. In the scientific method, an experiment is a procedure that arbitrates between competing models or hypotheses. Researchers also use experimentation to test existing theories or new hypotheses to support or disprove them, an experiment usually tests a hypothesis, which is an expectation about how a particular process or phenomenon works. However, an experiment may also aim to answer a question, without a specific expectation about what the experiment reveals. If an experiment is conducted, the results usually either support or disprove the hypothesis. According to some philosophies of science, an experiment can never prove a hypothesis, on the other hand, an experiment that provides a counterexample can disprove a theory or hypothesis. An experiment must also control the possible confounding factors—any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret the results, confounding is commonly eliminated through scientific controls and/or, in randomized experiments, through random assignment. In engineering and the sciences, experiments are a primary component of the scientific method. They are used to test theories and hypotheses about how physical processes work under particular conditions, typically, experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication. In medicine and the sciences, the prevalence of experimental research varies widely across disciplines. In contrast to norms in the sciences, the focus is typically on the average treatment effect or another test statistic produced by the experiment
4.
Budker Institute of Nuclear Physics
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The Budker Institute of Nuclear Physics is one of the major centres of advanced study of nuclear physics in Russia. It is located in the Siberian town Akademgorodok, on Academician Lavrentiev Avenue, the institute was founded by Gersh Itskovich Budker in 1959. Following his death in 1977, the institute was renamed in honour of Academician Budker, despite its name, the centre was not involved either with military atomic science or nuclear reactors— instead, its concentration was on high-energy physics and particle physics. The BINP now employs over 3000 people, and hosts several research groups and facilities. 4-2
5.
Novosibirsk
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Novosibirsk is the third-most populous city in Russia after Moscow and St. Petersburg. It is the most populous city in Asian Russia, with a population of 1,473,754 as of the 2010 Census and it is the administrative center of Novosibirsk Oblast as well as of the Siberian Federal District. It is split into ten districts and occupies an area of 502.1 square kilometers and it superseded nearby Krivoshchekovskaya village, which was founded in 1696. The bridge was completed in the spring of 1897, making the new settlement the regional transport hub, the importance of the city further increased with the completion of the Turkestan-Siberia Railway in the early 20th century. The new railway connected Novonikolayevsk to Central Asia and the Caspian Sea, at the time of the bridges opening, Novonikolayevsk had a population of 7,800 people. Its first bank opened in 1906, and a total of five banks were operating by 1915, in 1907, Novonikolayevsk, now with a population exceeding 47,000, was granted town status with full rights for self-government. During the pre-revolutionary period, the population of Novonikolayevsk reached 80,000, the city had steady and rapid economic growth, becoming one of the largest commercial and industrial centers of Siberia. It developed a significant agricultural processing industry, as well as a station, iron foundry, commodity market, several banks. In 1913, Novonikolayevsk became one of the first places in Russia to institute compulsory primary education, the Russian Civil War took a toll on the city. There were wartime epidemics, especially of typhus and cholera, that thousands of lives. In the course of the war the Ob River Bridge was destroyed, for the first time in the citys history, the population of Novonikolayevsk began to decline. The Soviet Workers and Soldiers Deputies of Novonikolayevsk took control of the city in December 1917, in May 1918, the Czechoslovak Legions rose in opposition to the revolutionary government and, together with the White Guards, captured Novonikolayevsk. The Red Army took the city in 1919, retaining it throughout the rest of the Civil War, Novonikolayevsk began reconstruction in 1921 at the start of Lenins New Economic Policy period. It was a part of Tomsk Governorate and served as its center from December 23,1919 to March 14,1920. Between June 13,1921 and May 25,1925, it served as the center of Novonikolayevsk Governorate. The city was given its present name on September 12,1926, since then, it has served as the administrative center of Novosibirsk Oblast. The Monument to the Heroes of the Revolution was erected in the center of the city and has one of the chief historic sites. Neglect in the 1990s while other areas were redeveloped helped preserve it in the post-Soviet era, during Joseph Stalins industrialization effort, Novosibirsk secured its place as one of the largest industrial centers of Siberia
6.
Russia
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Russia, also officially the Russian Federation, is a country in Eurasia. The European western part of the country is more populated and urbanised than the eastern. Russias capital Moscow is one of the largest cities in the world, other urban centers include Saint Petersburg, Novosibirsk, Yekaterinburg, Nizhny Novgorod. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a range of environments. It shares maritime borders with Japan by the Sea of Okhotsk, the East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, in 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus ultimately disintegrated into a number of states, most of the Rus lands were overrun by the Mongol invasion. The Soviet Union played a role in the Allied victory in World War II. The Soviet era saw some of the most significant technological achievements of the 20th century, including the worlds first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the second largest economy, largest standing military in the world. It is governed as a federal semi-presidential republic, the Russian economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2015. Russias extensive mineral and energy resources are the largest such reserves in the world, making it one of the producers of oil. The country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction, Russia is a great power as well as a regional power and has been characterised as a potential superpower. The name Russia is derived from Rus, a state populated mostly by the East Slavs. However, this name became more prominent in the later history, and the country typically was called by its inhabitants Русская Земля. In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus by modern historiography, an old Latin version of the name Rus was Ruthenia, mostly applied to the western and southern regions of Rus that were adjacent to Catholic Europe. The current name of the country, Россия, comes from the Byzantine Greek designation of the Kievan Rus, the standard way to refer to citizens of Russia is Russians in English and rossiyane in Russian. There are two Russian words which are translated into English as Russians
7.
Storage ring
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A storage ring is a type of circular particle accelerator in which a continuous or pulsed particle beam may be kept circulating typically for many hours. Storage of a particle depends upon the mass, momentum. Storage rings most commonly store electrons, positrons, or protons, storage rings are most often used to store electrons that radiate synchrotron radiation. Over 50 facilities based on storage rings exist and are used for a variety of studies in chemistry. Storage rings can also be used to produce polarized high-energy electron beams through the Sokolov-Ternov effect, the resulting subatomic interactions are then studied in a surrounding particle detector. Examples of such facilities are LHC, LEP, PEP-II, KEKB, RHIC, Tevatron, a storage ring is a type of synchrotron. Gerard K. ONeill proposed the use of rings as building blocks for a collider in 1956. A key benefit of storage rings in this context is that the ring can accumulate a high beam flux from an injection accelerator that achieves a much lower flux. A force must be applied to particles in such a way that they are constrained to move approximately in a circular path. However, electrostatic accelerators have been built to very low energy particles, and quadrupole fields may be used to store neutrons. Dipole magnets alone only provide what is called weak focusing, interleaving dipole magnets with an appropriate arrangement of quadrupole and sextupole magnets can give a suitable strong focusing system that can give a much smaller beam size. The FODO and Chasman-Green lattice structures are examples of strong focusing systems. Dipole and quadrupole magnets deflect different particle energies by differing amounts, sextupole magnets are used to correct for this phenomenon, but this in turn gives rise to nonlinear motion that is one of the main problems facing designers of storage rings. As the bunches will travel many millions of kilometers, any gas in the beam pipe will result in many, many collisions. This will have the effect of increasing the size of the bunch, therefore, a better vacuum yields better beam dynamics. This gradual loss of particles is called beam lifetime, and means that storage rings must be injected with a new complement of particles. Injection of particles into a ring may be accomplished in a number of ways. This method is sometimes called single-turn injection, multi-turn injection allows accumulation of many incoming trains of particles, for example if a large stored current is required
8.
Energy
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In physics, energy is the property that must be transferred to an object in order to perform work on – or to heat – the object, and can be converted in form, but not created or destroyed. The SI unit of energy is the joule, which is the transferred to an object by the mechanical work of moving it a distance of 1 metre against a force of 1 newton. Mass and energy are closely related, for example, with a sensitive enough scale, one could measure an increase in mass after heating an object. Living organisms require available energy to stay alive, such as the humans get from food. Civilisation gets the energy it needs from energy resources such as fuels, nuclear fuel. The processes of Earths climate and ecosystem are driven by the radiant energy Earth receives from the sun, the total energy of a system can be subdivided and classified in various ways. It may also be convenient to distinguish gravitational energy, thermal energy, several types of energy, electric energy. Many of these overlap, for instance, thermal energy usually consists partly of kinetic. Some types of energy are a mix of both potential and kinetic energy. An example is energy which is the sum of kinetic. Whenever physical scientists discover that a phenomenon appears to violate the law of energy conservation. Heat and work are special cases in that they are not properties of systems, in general we cannot measure how much heat or work are present in an object, but rather only how much energy is transferred among objects in certain ways during the occurrence of a given process. Heat and work are measured as positive or negative depending on which side of the transfer we view them from, the distinctions between different kinds of energy is not always clear-cut. In contrast to the definition, energeia was a qualitative philosophical concept, broad enough to include ideas such as happiness. The modern analog of this property, kinetic energy, differs from vis viva only by a factor of two, in 1807, Thomas Young was possibly the first to use the term energy instead of vis viva, in its modern sense. Gustave-Gaspard Coriolis described kinetic energy in 1829 in its modern sense, the law of conservation of energy was also first postulated in the early 19th century, and applies to any isolated system. It was argued for years whether heat was a physical substance, dubbed the caloric, or merely a physical quantity. In 1845 James Prescott Joule discovered the link between mechanical work and the generation of heat and these developments led to the theory of conservation of energy, formalized largely by William Thomson as the field of thermodynamics
9.
Annihilation
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The total energy and momentum of the initial pair are conserved in the process, and, more generally are distributed among a set of other particles in the final state. Antiparticles have exactly opposite additive quantum numbers from particles, so the sums of all numbers of such an original pair are zero. Hence, any set of particles may be produced whose total numbers are also zero as long as conservation of energy. During a low-energy annihilation, photon production is favored, since these particles have no mass, however, high-energy particle colliders produce annihilations where a wide variety of exotic heavy particles are created. The word annihilation may also be used informally for the interaction of two particles that are not mutual antiparticles, some quantum numbers may then not sum to zero in the initial state, but must be conserved, with the same totals in the final state. An example is the annihilation of an electron antineutrino with an electron to produce a W−. If the annihilating particles are composite, such as mesons or baryons, if the initial two particles are elementary, then they may combine to produce only a single elementary boson, such as a photon, gluon, Z, or a Higgs boson. If the total energy in the frame is equal to the rest mass of a real boson. Otherwise, the process is understood as the creation of a boson that is virtual. This is called an s-channel process, an example is the annihilation of an electron with a positron to produce a virtual photon, which converts into a muon and anti-muon. If the energy is enough, a Z could replace the photon. Both the annihilating electron and positron particles have a rest energy of about 0.511 million electron volts, if their kinetic energies are relatively negligible, this total rest energy appears as the photon energy of the gamma rays produced. Each of the gamma rays then has an energy of about 0.511 MeV, momentum and energy are both conserved, with 1.022 MeV of gamma rays moving in opposite directions. If one or both charged particles carry a larger amount of energy, various other particles can be produced. The inverse process, pair production by a real photon, is also possible in the electromagnetic field of a third particle. When a proton encounters its antiparticle, the reaction is not as simple as electron-positron annihilation, unlike an electron, a proton is a composite particle consisting of three valence quarks and an indeterminate number of sea quarks bound by gluons. This type of reaction will occur between any baryon and any antibaryon consisting of three antiquarks, one of which corresponds to a quark in the baryon, antiprotons can and do annihilate with neutrons, and likewise antineutrons can annihilate with protons, as discussed below. Reactions in which proton-antiproton annihilation produces as many as nine mesons have been observed, the generated mesons leave the site of the annihilation at moderate fractions of the speed of light, and decay with whatever lifetime is appropriate for their type of meson
10.
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
11.
Anomalous magnetic dipole moment
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The Dirac magnetic moment, corresponding to tree-level Feynman diagrams, can be calculated from the Dirac equation. It is usually expressed in terms of the g-factor, the Dirac equation predicts g =2, for particles such as the electron, this classical result differs from the observed value by a small fraction of a percent. The calculation is relatively straightforward and the result is, a e = α2 π ≈0.0011614 where α is the fine structure constant. This result was first found by Julian Schwinger in 1948 and is engraved on his tombstone. As of 2016, the coefficients of the QED formula for the magnetic moment of the electron are known analytically up to α3 and have been calculated up to order α5. The current experimental value and uncertainty is, a e =0.00115965218073 According to this value and this required measuring g to an accuracy of around 1 part in 1 trillion. The anomalous magnetic moment of the muon is calculated in a way to the electron. The third term represents hadron loops, and cannot be calculated accurately from theory alone and it is estimated from experimental measurements of the ratio of hadronic to muonic cross sections in electron–antielectron collisions. As of November 2006, the measurement disagrees with the Standard Model by 3.4 standard deviations and this is one of the long-standing discrepancies between the Standard Model and experiment. The E821 experiment at Brookhaven National Laboratory studied the precession of muon and antimuon in a constant external magnetic field as they circulated in a storage ring. The E821 Experiment reported the average value a μ =0.00116592091, where the first error is statistical. A new experiment at Fermilab called Muon g−2 using the E821 magnet will improve the accuracy of this value, data taking will begin in 2017. A measurement with a precision 4 times better is expected after years of running and this is true for the proton, which is made up of charged quarks, and the neutron, which has a magnetic moment even though it is electrically neutral. Anomalous electric dipole moment G-factor Proton magnetic moment Neutron magnetic moment Electron magnetic moment Sergei Vonsovsky, overview of the g−2 experiment Kusch, P. Foley, H. M. The Magnetic Moment of the Electron
12.
Quantum electrodynamics
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In particle physics, quantum electrodynamics is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved, in technical terms, QED can be described as a perturbation theory of the electromagnetic quantum vacuum. Dirac described the quantization of the field as an ensemble of harmonic oscillators with the introduction of the concept of creation and annihilation operators of particles. At higher orders in the series emerged, making such computations meaningless. With no solution for this problem known at the time, it appeared that a fundamental incompatibility existed between special relativity and quantum mechanics, difficulties with the theory increased through the end of 1940. Improvements in microwave technology made it possible to more precise measurements of the shift of the levels of a hydrogen atom, now known as the Lamb shift. These experiments exposed discrepancies which the theory was unable to explain, a first indication of a possible way out was given by Hans Bethe in 1947, after attending the Shelter Island Conference. While he was traveling by train from the conference to Schenectady he made the first non-relativistic computation of the shift of the lines of the atom as measured by Lamb. Despite the limitations of the computation, agreement was excellent, the idea was simply to attach infinities to corrections of mass and charge that were actually fixed to a finite value by experiments. In this way, the infinities get absorbed in those constants, sin-Itiro Tomonaga, Julian Schwinger and Richard Feynman were jointly awarded with a Nobel prize in physics in 1965 for their work in this area. Even though renormalization works very well in practice, Feynman was never comfortable with its mathematical validity, even referring to renormalization as a shell game. QED has served as the model and template for all subsequent quantum field theories. One such subsequent theory is quantum chromodynamics, which began in the early 1960s and attained its present form in the 1975 work by H. David Politzer, Sidney Coleman, David Gross and Frank Wilczek. Near the end of his life, Richard P. Feynman gave a series of lectures on QED intended for the lay public. These lectures were transcribed and published as Feynman, QED, The strange theory of light and matter, the key components of Feynmans presentation of QED are three basic actions. A photon goes from one place and time to another place, an electron goes from one place and time to another place and time. An electron emits or absorbs a photon at a certain place and these can all be seen in the adjacent diagram. It is important not to over-interpret these diagrams, nothing is implied about how a particle gets from one point to another
13.
Sodium iodide
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Sodium iodide is the salt of sodium and iodide. It is a white, crystalline solid that is used mainly as a nutritional supplement and it is produced industrially by acidic iodides and sodium hydroxide. Sodium iodide, as well as potassium iodide, is used to treat. Iodized table salt contains one part sodium or potassium iodide to 100,000 parts of sodium chloride, sodium iodide is used for conversion of an alkyl chlorides into an alkyl iodides. NaI is the most widely used scintillation material, the crystals are usually coupled with a photomultiplier tube, in a hermetically sealed assembly, as sodium iodide is hygroscopic. Fine-tuning of some parameters can be achieved by varying the conditions of the crystal growth, crystals with a higher level of doping are used in X-ray detectors with high spectrometric quality. Sodium iodide can be used both as single crystals and as polycrystals for this purpose, the wavelength of maximum emission is 415 nm. Sodium iodide exhibits high solubility in organic solvents, unlike sodium chloride or even bromide
14.
Particle decay
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Particle decay is the spontaneous process of one unstable subatomic particle transforming into multiple other particles. The particles created in this process must each be less massive than the original, a particle is unstable if there is at least one allowed final state that it can decay into. Unstable particles will often have multiple ways of decaying, each with its own associated probability, decays are mediated by one or several fundamental forces. The particles in the state may themselves be unstable and subject to further decay. All data is from the Particle Data Group, note that this section uses natural units, where c = ℏ =1. The lifetime of a particle is given by the inverse of its rate, Γ. One may integrate over the space to obtain the total decay rate for the specified final state. If a particle has multiple decay branches or modes with different final states, the branching ratio for each mode is given by its decay rate divided by the full decay rate. Note that this section uses natural units, where c = ℏ =1, say a parent particle of mass M decays into two particles, labeled 1 and 2. In the rest frame of the parent particle, | p →1 | = | p →2 | =1 /22 M, also, in spherical coordinates, d 3 p → = | p → |2 d | p → | d ϕ d. The mass of a particle is formally a complex number, with the real part being its mass in the usual sense. When the imaginary part is large compared to the real part, for a particle of mass M + i Γ, the particle can travel for time 1/M, but decays after time of order of 1 / Γ. If Γ > M then the particle usually decays before it completes its travel, relativistic Breit-Wigner distribution Particle physics List of particles Weak interaction J. D. Jackson. The Particle Adventure Particle Data Group, Lawrence Berkeley National Laboratory
15.
Luminosity
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In astronomy, luminosity is the total amount of energy emitted by a star, galaxy, or other astronomical object per unit time. It is related to the brightness, which is the luminosity of an object in a spectral region. In SI units luminosity is measured in joules per second or watts, values for luminosity are often given in the terms of the luminosity of the Sun, which has a total power output of 7026384600000000000♠3. 846×1026 W. The symbol for solar luminosity is L⊙. Luminosity can also be given in terms of magnitude, the absolute bolometric magnitude of an object is a logarithmic measure of its total energy emission. In astronomy, luminosity is the amount of energy a body radiates per unit of time. It is most frequently measured in two forms, visual and bolometric, although luminosities at other wavelengths are increasingly being used as instruments become available to measure them, a bolometer is the instrument used to measure radiant energy over a wide band by absorption and measurement of heating. When not qualified, the term luminosity means bolometric luminosity, which is measured either in the SI units, watts, a star also radiates neutrinos, which carry off some energy, contributing to the stars total luminosity. In practice bolometric magnitudes are measured by taking measurements at certain wavelengths, a stars luminosity can be determined from two stellar characteristics, size and effective temperature. The former is represented in terms of solar radii, R⊙, while the latter is represented in kelvins. To determine a stars radius, two metrics are needed, the stars angular diameter and its distance from Earth, often calculated using parallax. However, for most stars the angular diameter or parallax, or both, are far below our ability to measure with any certainty, an alternate way to measure stellar luminosity is to measure the stars apparent brightness and distance. Because luminosity is proportional to temperature to the power, the large variation in stellar temperatures produces an even vaster variation in stellar luminosity. Because the luminosity depends on a power of the stellar mass. The most luminous stars are young stars, no more than a few million years for the most extreme. In the Hertzsprung–Russell diagram, the x-axis represents temperature or spectral type while the y-axis represents luminosity or magnitude. The vast majority of stars are found along the sequence with blue Class 0 stars found at the top left of the chart while red Class M stars fall to the bottom right. Certain stars like Deneb and Betelgeuse are found above and to the right of the main sequence, blue and white supergiants are high luminosity stars somewhat cooler than the most luminous main sequence stars. A star like Deneb, for example, has a luminosity around 200,000 L⊙, a type of A2
16.
ArXiv
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In many fields of mathematics and physics, almost all scientific papers are self-archived on the arXiv repository. Begun on August 14,1991, arXiv. org passed the half-million article milestone on October 3,2008, by 2014 the submission rate had grown to more than 8,000 per month. The arXiv was made possible by the low-bandwidth TeX file format, around 1990, Joanne Cohn began emailing physics preprints to colleagues as TeX files, but the number of papers being sent soon filled mailboxes to capacity. Additional modes of access were added, FTP in 1991, Gopher in 1992. The term e-print was quickly adopted to describe the articles and its original domain name was xxx. lanl. gov. Due to LANLs lack of interest in the rapidly expanding technology, in 1999 Ginsparg changed institutions to Cornell University and it is now hosted principally by Cornell, with 8 mirrors around the world. Its existence was one of the factors that led to the current movement in scientific publishing known as open access. Mathematicians and scientists regularly upload their papers to arXiv. org for worldwide access, Ginsparg was awarded a MacArthur Fellowship in 2002 for his establishment of arXiv. The annual budget for arXiv is approximately $826,000 for 2013 to 2017, funded jointly by Cornell University Library, annual donations were envisaged to vary in size between $2,300 to $4,000, based on each institution’s usage. As of 14 January 2014,174 institutions have pledged support for the period 2013–2017 on this basis, in September 2011, Cornell University Library took overall administrative and financial responsibility for arXivs operation and development. Ginsparg was quoted in the Chronicle of Higher Education as saying it was supposed to be a three-hour tour, however, Ginsparg remains on the arXiv Scientific Advisory Board and on the arXiv Physics Advisory Committee. The lists of moderators for many sections of the arXiv are publicly available, additionally, an endorsement system was introduced in 2004 as part of an effort to ensure content that is relevant and of interest to current research in the specified disciplines. Under the system, for categories that use it, an author must be endorsed by an established arXiv author before being allowed to submit papers to those categories. Endorsers are not asked to review the paper for errors, new authors from recognized academic institutions generally receive automatic endorsement, which in practice means that they do not need to deal with the endorsement system at all. However, the endorsement system has attracted criticism for allegedly restricting scientific inquiry, perelman appears content to forgo the traditional peer-reviewed journal process, stating, If anybody is interested in my way of solving the problem, its all there – let them go and read about it. The arXiv generally re-classifies these works, e. g. in General mathematics, papers can be submitted in any of several formats, including LaTeX, and PDF printed from a word processor other than TeX or LaTeX. The submission is rejected by the software if generating the final PDF file fails, if any image file is too large. ArXiv now allows one to store and modify an incomplete submission, the time stamp on the article is set when the submission is finalized
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Particle detector
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Detectors can measure the particle energy and other attributes such as momentum, spin, charge, in addition to merely registering the presence of the particle. Detectors designed for modern accelerators are huge, both in size and in cost, the term counter is often used instead of detector when the detector counts the particles but does not resolve its energy or ionization. Particle detectors can also usually track ionizing radiation, if their main purpose is radiation measurement, they are called radiation detectors, but as photons are also particles, the term particle detector is still correct. A New Classification System for Radiation Detectors, journal of the Optical Society of America. Erratum, The Ultimate Sensitivity of Radiation Detectors, journal of the Optical Society of America. Factors of Merit for Radiation Detectors, journal of the Optical Society of America. AIP Conference Proceedings, Instrumentation in Elementary Particle Physics, VIII, istanbul, Dordrecht, D. Reidel Publishing Co. pp. 3–34
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Experimental physics
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Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments. Methods vary from discipline to discipline, from experiments and observations, such as the Cavendish experiment, to more complicated ones. It is often put in contrast with theoretical physics, which is concerned with predicting and explaining the physical behaviour of nature than the acquisition of knowledge about it. Although experimental and theoretical physics are concerned with different aspects of nature, theoretical physics can also offer insight on what data is needed in order to gain a better understanding of the universe, and on what experiments to devise in order to obtain it. In the early 17th century, Galileo made extensive use of experimentation to validate physical theories, Galileo formulated and successfully tested several results in dynamics, in particular the law of inertia, which later became the first law in Newtons laws of motion. In Galileos Two New Sciences, a dialogue between the characters Simplicio and Salviati discuss the motion of a ship and how that ships cargo is indifferent to its motion. Huygens used the motion of a boat along a Dutch canal to illustrate a form of the conservation of momentum. Experimental physics is considered to have reached a point with the publication of the Philosophiae Naturalis Principia Mathematica in 1687 by Sir Isaac Newton. Both theories agreed well with experiment, the Principia also included several theories in fluid dynamics. From the late 17th century onward, thermodynamics was developed by physicist and chemist Boyle, Young, in 1733, Bernoulli used statistical arguments with classical mechanics to derive thermodynamic results, initiating the field of statistical mechanics. In 1798, Thompson demonstrated the conversion of work into heat. Ludwig Boltzmann, in the century, is responsible for the modern form of statistical mechanics. Besides classical mechanics and thermodynamics, another field of experimental inquiry within physics was the nature of electricity. Observations in the 17th and eighteenth century by such as Robert Boyle, Stephen Gray. These observations also established our basic understanding of electrical charge and current, by 1808 John Dalton had discovered that atoms of different elements have different weights and proposed the modern theory of the atom. It was Hans Christian Ørsted who first proposed the connection between electricity and magnetism after observing the deflection of a needle by a nearby electric current. By the early 1830s Michael Faraday had demonstrated that magnetic fields, in 1864 James Clerk Maxwell presented to the Royal Society a set of equations that described this relationship between electricity and magnetism. Maxwells equations also predicted correctly that light is an electromagnetic wave, starting with astronomy, the principles of natural philosophy crystallized into fundamental laws of physics which were enunciated and improved in the succeeding centuries
19.
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
. doi:10.1063/1.1482433.
