The L3 experiment was one of the four large detectors on the Large Electron-Positron Collider. The detector was designed to look for the physics of the Standard Model and it started up in 1989 and stopped taking data in November 2000 to make room for construction of the Large Hadron Collider. Now, the ALICE detector sits in the cavern that L3 used to occupy, the L3-detector was a multi-layered cylindrical set of different devices, each of them measuring physical quantities relevant to the reconstruction of the collision under study. Starting from the centre, close to the pipe where electrons and positrons circulate and collide, there were first the Silicon strip Microvertex Detector and these two sub-detectors traced the paths of charged particles produced in the collision. One gathered information about the momentum of the particles by measuring their deflection in the field present in the detector. The three main outer layers were the electro-magnetic calorimeter, the calorimeter and the muon detector.
Calorimeters are dense and stop most particles, measuring their energy, the outermost layer contained the magnet that generated, inside the detector, a magnetic field about 10000 times the average field on the surface of the Earth. This field deflected the particles which crossed it and the curvature of this deflection was a way of reconstructing the energy of the particles. Another important part of the detector were the two luminosity monitors, placed along the beam on both sides of the interaction point and they measured the luminosity of the beam, which is a way of quantifying the rate of interactions produced. Official website Scientific publications of the L3 Collaboration on INSPIRE-HEP
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, made of three quarks, and mesons, made of one quark and one antiquark 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 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 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 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 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, 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
NA61/SHINE is a particle physics experiment at the Super Proton Synchrotron at the European Organization for Nuclear Research. The experiment studies the hadronic final states produced in interactions of various beam particles with a variety of fixed nuclear targets at the SPS energies, about 135 physicists from 14 countries and 35 institutions work in NA61/SHINE, led by Marek Gazdzicki. NA61/SHINE is the second largest fixed target experiment at CERN, in hadron–nucleus interactions needed for neutrino and cosmic-ray experiments. The NA61/SHINE experiment uses a large acceptance hadron spectrometer located on the H2 beam line in the North Area of CERN and it consist of components used by the heavy ion NA49 experiment as well as those designed and constructed for NA61/SHINE. The main tracking devices are four large volume time projection chambers, two of them are located in the magnetic field of two super-conducting dipole magnets with maximum bending powers of 9 Tesla meters. Two others are positioned downstream of the magnets symmetrically with respect to the beam line, the setup is supplemented by time of flight detector walls, which extend particle identification to low momenta.
Furthermore, the Projectile Spectator Detector is positioned downstream of the time of flight detectors to measure energy of projectile fragments, list of Super Proton Synchrotron experiments NA61/SHINE Collaboration web-site NA61/SHINE proposal NA49 Collaboration web-site
The NA58 experiment, or COMPASS is a 60-metre-long fixed-target experiment at the M2 beam line of the SPS at CERN. The experimental hall is located at the CERN North Area, close to the French village of Prévessin-Moëns, the experiment is a two-staged spectrometer with numerous tracking detectors, particle identification and calorimetry. The physics results are extracted by recording and analysing the final states of the scattering processes, the versatile set-up, the use of different targets and particle beams allow the investigation of various processes. The main physics goals are the investigation of the spin structure. The collaboration consists of 220 physicists from 13 different countries, involving 28 universities, the COMPASS experiment was proposed in 1996 and approved by the CERN research committee. Between 1999 and 2001, the experiment was set up and finally in 2001, until the start of the LHC experiments, COMPASS was the largest data-taking experiment at CERN. It is a pioneer in adopting new detector and readout technologies, such as MicroMegas, GEM detectors, the data taking is divided into the COMPASS I and II phases.
The M2 beam line is able to produce various particle beams, the primary proton beam is steered on a beryllium production target producing secondary hadrons, mainly consisting of protons and kaons. In all cases, the beam is steered with dipole magnets and focused with quadrupole magnets to reached the desired position, the timing and the position of the incident particles are determined with cold silicon strip detectors and scintillating fibre detectors. These informations are crucial to determine the point inside the target material. According to the goal, a suitable target is needed. For polarised physics, the spins of the material need to be oriented in one direction. The target cell contains either ammonium or deuterium, which are polarised by the means of microwave radiation, to keep up the polarisation grade, a 3He/4He dilution refrigerator is used to cool down the target material to 50 mK. The target material can be polarised longitudinal or transverse to the beam axis, for unpolarised physics, mostly liquid hydrogen is used, allowing to study the proton properties.
For other physics, where high atomic numbers are needed, lead, the main advantage of a fixed target experiment is the large acceptance. Due to the Lorentz boost, most of the final states and this leads to the distinctive set-up of a fixed-target experiment, most detectors are placed behind the target. For some processes it is necessary to detect the recoil nucleon from the target, here, a recoil proton detector consisting of two barrels of scintillator material is used. The protons are identified by the time of flight and the energy loss, the COMPASS experiment consists of two spectrometer stages with various tracking detector types, each set-up around a spectrometer magnet to determine the momentum of the particles
Super Proton Synchrotron
The Super Proton Synchrotron is a particle accelerator of the synchrotron type at CERN. It is housed in a tunnel,6.9 kilometres in circumference, straddling the border of France and Switzerland near Geneva. The SPS was designed by a led by John Adams. Originally specified as a 300 GeV accelerator, the SPS was actually built to be capable of 400 GeV, however, by that time, this energy had been exceeded by Fermilab, which reached an energy of 500 GeV on 14 May of that year. The SPS has been used to accelerate protons and antiprotons and positrons, and heavy ions. From 1981 to 1984, the SPS operated as a hadron collider, when its beams provided the data for the UA1 and UA2 experiments and these discoveries and a new technique for cooling particles led to a Nobel Prize for Carlo Rubbia and Simon van der Meer in 1984. The LHC itself accelerates them to several teraelectronvolts, the SPS is being used by the CNGS experiment to produce a neutrino stream to be detected at the Gran Sasso laboratory in Italy,730 km from CERN.
The SPS has served as a test bench for new concepts in accelerator physics, in 1999 it served as an observatory for the electron cloud phenomenon. In 2003, SPS was the first machine where the Hamiltonian resonance driving terms were directly measured, and in 2004, experiments to cancel the detrimental effects of beam encounters were carried out. Major scientific discoveries made by experiments that operated at the SPS include the following,1983, The discovery of W and Z bosons in the UA1 and UA2 experiments. The 1984 Nobel Prize in physics was awarded to Carlo Rubbia,1999, The discovery of direct CP violation by the NA48 experiment. The Large Hadron Collider will require an upgrade to increase its luminosity by the 2020s. This would require upgrades to the entire chain, including the SPS. The SPS will need to be able to handle a higher intensity beam. One improvement considered in the past was increasing the energy to 1 TeV. However, the energy will be kept at 450 GeV while other systems are upgraded.
The acceleration system will be modified to handle the higher voltages needed to accelerate a higher intensity beam, the beam dumping system will be upgraded so it can accept a higher intensity beam without sustaining significant damage
Fermi National Accelerator Laboratory, located just outside Batavia, near Chicago, is a United States Department of Energy national laboratory specializing in high-energy particle physics. Since 2007, Fermilab has been operated by the Fermi Research Alliance, a joint venture of the University of Chicago, Fermilab is a part of the Illinois Technology and Research Corridor. Fermilabs Tevatron was a particle accelerator, at 3.9 miles in circumference, it was the worlds fourth-largest particle accelerator. In 1995, the discovery of the top quark was announced by researchers who used the Tevatrons CDF, in addition to high-energy collider physics, Fermilab hosts fixed-target and neutrino experiments, such as MicroBooNE, NOνA and SeaQuest. Completed neutrino experiments include MINOS, MINOS+, MiniBooNE and SciBooNE, the MiniBooNE detector was a 40-foot diameter sphere containing 800 tons of mineral oil lined with 1,520 phototube detectors. An estimated 1 million neutrino events were recorded each year, SciBooNE sat in the same neutrino beam as MiniBooNE but had fine-grained tracking capabilities.
In the public realm, Fermilab hosts many events, not only public science lectures and symposia. The site is open dawn to dusk to visitors who present valid photo identification. Asteroid 11998 Fermilab is named in honor of the laboratory, Illinois, was a community next to Batavia voted out of existence by its village board in 1966 to provide a site for Fermilab. The laboratory was founded in 1967 as the National Accelerator Laboratory, the laboratorys first director was Robert Rathbun Wilson, under whom the laboratory opened ahead of time and under budget. Many of the sculptures on the site are of his creation and he is the namesake of the sites high-rise laboratory building, whose unique shape has become the symbol for Fermilab and which is the center of activity on the campus. After Wilson stepped down in 1978 to protest the lack of funding for the lab and it was under his guidance that the original accelerator was replaced with the Tevatron, an accelerator capable of colliding protons and antiprotons at a combined energy of 1.96 TeV.
Lederman stepped down in 1989 and remains Director Emeritus, the science education center at the site was named in his honor. The directors include, John Peoples,1989 to 1999 Michael S, as of 2014, the first stage in the acceleration process takes place in two ion sources which turn hydrogen gas into H− ions. A magnetron generates a plasma to form the ions near the metal surface, at the exit of RFQ, the beam is matched by medium energy beam transport into the entrance of the linear accelerator. The next stage of acceleration is linear particle accelerator and this stage consists of two segments. The first segment has 5 vacuum vessel for drift tubes, operating at 201 MHz, the second stage has 7 side-coupled cavities, operating at 805 MHz. At the end of linac, the particles are accelerated to 400 MeV, immediately before entering the next accelerator, the H− ions pass through a carbon foil, becoming H+ ions
ALEPH was a particle detector at the Large Electron-Positron collider. It was designed to explore the physics predicted by the Standard Model, the ALEPH detector was built to measure events created by electron positron collisions in LEP. It operated from 1989 to 1995 in the range of the Z particle. Typical events have many particles distributed in jets over the detector volume. The event rate ranged from around 1 Hz at the peak of the Z to at least a hundred smaller at the highest energies. The ALEPH detector was designed to accumulate, for each event. This was achieved by a cylindrical arrangement around the pipe with the electron-positron interaction point in the middle. A magnetic field of 1.5 Tesla was created by a superconducting coil 6.4 m long and 5.3 m in diameter, the iron return yoke was a dodecagonal cylinder with two end-plates that left holes for a focusing magnet of the LEP machine. The iron was 1.2 m thick and was subdivided into layers that left space for the insertion of layers of streamer tubes, in this way the iron yoke was a fully instrumented hadron calorimeter, which was read out in 4608 projective towers.
Outside the iron, there were two layers of streamer tube chambers to record the position and angle of muons that had penetrated the iron. Inside the coil was the electron-photon calorimeter, designed for the highest possible resolution and electron identification. It consisted of alternating layers of lead and proportional tubes read out in 73,728 projective towers, the central detector for charged particles was the time projection chamber,4.4 m long and 3.6 m in diameter. It provided a three dimensional measurement of each track segment, in addition, it provided up to 330 ionisation measurements for a track, this was useful for particle identification. The TPC surrounded the inner chamber, an axial-wire drift chamber with inner and outer diameters of 13 cm and 29 cm. It provided 8 track coordinates and a signal for charged particles that came from the interaction point. Closest to the pipe, was a silicon strip vertex detector. For each track, this measured two pairs of coordinates,6.3 cm and 11 cm away from the beam axis over a length of 40 cm along the beam line, the beam pipe, made out of beryllium, had a diameter of 16 cm.
The vacuum inside was about 10−15 atm, official website Scientific publications of the ALEPH Collaboration on INSPIRE-HEP
The LHCf is a special-purpose Large Hadron Collider experiment for astroparticle physics, and one of seven detectors in the LHC accelerator at CERN. The other six are, ATLAS, ALICE, CMS, MoEDAL, TOTEM, LHCf is designed to study the particles generated in the forward region of collisions, those almost directly in line with the colliding proton beams. It therefore consists of two detectors,140 m on either side of the interaction point, the LHCf is intended to measure the energy and numbers of neutral pions produced by the collider. This will hopefully help explain the origin of cosmic rays. The results will complement other high-energy cosmic ray measurements from the Pierre Auger Observatory in Argentina, LHCf section on US/LHC Website LHCf, a tiny new experiment joins the LHC, CERN Courier, Nov 1,2006, retrieved on 2009-03-25. The LHCf experiment at LHC Technical Design Report of LHCf O Adriani et al, the LHCf detector at the CERN Large Hadron Collider. LHCf detector performance during the 2009-2010 LHC run, international Journal of Modern Physics A.28, 1330036-1
DELPHI was one of the four main detectors of the Large Electron–Positron Collider at CERN, one of the largest particle accelerators ever made. Like the other three detectors, it recorded and analyzed the result of the collision between LEPs colliding particle beams, DELPHI had the shape of a cylinder over 10 metres in length and diameter, and a weight of 3500 tons. In operation and positrons from the accelerator went through a pipe going through the center of the cylinder, DELPHI was constructed between 1983 and 1988, and LEP started operation in 1989. After LEP was decommissioned in November 2000, DELPHI began to be dismantled, official website Scientific publications of the DELPHI Collaboration on INSPIRE-HEP
Large Hadron Collider
The Large Hadron Collider is the worlds largest and most powerful particle collider, most complex experimental facility ever built, and the largest single machine in the world. It lies in a tunnel 27 kilometres in circumference, as deep as 175 metres beneath the France–Switzerland border near Geneva, on 13 February 2013 the LHCs first run officially ended, and it was shut down for planned upgrades. Test collisions restarted in the collider on 5 April 2015. Its second research run commenced on schedule, on 3 June 2015, the collider has four crossing points, around which are positioned seven detectors, each designed for certain kinds of research. The LHC primarily collides proton beams, but it can use beams of lead nuclei, proton–lead collisions were performed for short periods in 2013 and 2016, and lead–lead collisions took place in 2010,2011,2013, and 2015. The LHCs computing grid is a record holder. The term hadron refers to composite particles composed of quarks held together by the strong force, a collider is a type of a particle accelerator with two directed beams of particles.
In particle physics, colliders are used as a tool, they accelerate particles to very high kinetic energies. Analysis of the byproducts of these collisions gives scientists good evidence of the structure of the subatomic world, many of these byproducts are produced only by high-energy collisions, and they decay after very short periods of time. Thus many of them are hard or nearly impossible to study in other ways, many theorists expect new physics beyond the Standard Model to emerge at the TeV energy level, as the Standard Model appears to be unsatisfactory. Issues possibly to be explored by LHC collisions include, Are the masses of particles actually generated by the Higgs mechanism via electroweak symmetry breaking. The experiments found a particle appears to be the Higgs boson. Is supersymmetry, an extension of the Standard Model and Poincaré symmetry, realized in nature, are there extra dimensions, as predicted by various models based on string theory, and can we detect them. What is the nature of the matter that appears to account for 27% of the mass-energy of the universe.
Why is the fundamental force so many orders of magnitude weaker than the other three fundamental forces. Are there additional sources of quark mixing, beyond those already present within the Standard Model. Why are there apparent violations of the symmetry between matter and antimatter, what are the nature and properties of quark–gluon plasma, thought to have existed in the early universe and in certain compact and strange astronomical objects today. This will be investigated by heavy ion collisions, mainly in ALICE, first observed in 2010, findings published in 2012 confirmed the phenomenon of jet quenching in heavy-ion collisions