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A collider is a type of particle accelerator that brings two opposing particle beams together such that the particles collide. Colliders may either be ring accelerators or linear accelerators.
In particle physics, a glueball is a hypothetical composite particle. It consists solely of gluon particles, without valence quarks. Such a state is possible because gluons carry color charge and experience the strong interaction between themselves. Glueballs are extremely difficult to identify in particle accelerators, because they mix with ordinary meson states. In pure gauge theory, glueballs are the only states of the spectrum and some of them are stable.
In physics, the pomeron is a Regge trajectory — a family of particles with increasing spin — postulated in 1961 to explain the slowly rising cross section of hadronic collisions at high energies. It is named after Isaak Pomeranchuk.
In quantum physics, Regge theory is the study of the analytic properties of scattering as a function of angular momentum, where the angular momentum is not restricted to be an integer multiple of ħ but is allowed to take any complex value. The nonrelativistic theory was developed by Tullio Regge in 1959.
Hadronization is the process of the formation of hadrons out of quarks and gluons. There are two main branches of hadronization: quark-gluon plasma (QGP) transformation and colour string decay into hadrons. The transformation of quark-gluon plasma into hadrons is studied in lattice QCD numerical simulations, which are explored in relativistic heavy-ion experiments. Quark-gluon plasma hadronization occurred shortly after the Big Bang when the quark–gluon plasma cooled down to the Hagedorn temperature when free quarks and gluons cannot exist. In string breaking new hadrons are forming out of quarks, antiquarks and sometimes gluons, spontaneously created from the vacuum.
Two-photon physics, also called gamma–gamma physics, is a branch of particle physics that describes the interactions between two photons. Normally, beams of light pass through each other unperturbed. Inside an optical material, and if the intensity of the beams is high enough, the beams may affect each other through a variety of non-linear effects. In pure vacuum, some weak scattering of light by light exists as well. Also, above some threshold of this center-of-mass energy of the system of the two photons, matter can be created.
The TOTEM experiment is one of the nine detector experiments at CERN's Large Hadron Collider. The other eight are: ATLAS, ALICE, CMS, LHCb, LHCf, MoEDAL, FASER and SND@LHC. It shares an interaction point with CMS. The detector aims at measurement of total cross section, elastic scattering, and diffraction processes. The primary instrument of the detector is referred to as a Roman pot. In December 2020, the D0 and TOTEM Collaborations made public the odderon discovery based on a purely data driven approach in a CERN and Fermilab approved preprint that was later published in Physical Review Letters. In this experimental observation, the TOTEM proton-proton data in the region of the diffractive minimum and maximum was extrapolated from 13, 8, 7 and 2.76 TeV to 1.96 TeV and compared this to D0 data at 1.96 TeV in the same t-range giving an odderon significance of 3.4 σ. When combined with TOTEM experimental data at 13 TeV at small scattering angles providing an odderon significance of 3.4 - 4.6 σ, the combination resulted in an odderon significance of at least 5.2 σ.
The Drell–Yan process occurs in high energy hadron–hadron scattering. It takes place when a quark of one hadron and an antiquark of another hadron annihilate, creating a virtual photon or Z boson which then decays into a pair of oppositely-charged leptons. Importantly, the energy of the colliding quark-antiquark pair can be almost entirely transformed into the mass of new particles. This process was first suggested by Sidney Drell and Tung-Mow Yan in 1970 to describe the production of lepton–antilepton pairs in high-energy hadron collisions. Experimentally, this process was first observed by J. H. Christenson et al. in proton–uranium collisions at the Alternating Gradient Synchrotron.
The DØ experiment was a worldwide collaboration of scientists conducting research on the fundamental nature of matter. DØ was one of two major experiments located at the Tevatron Collider at Fermilab in Batavia, Illinois. The Tevatron was the world's highest-energy accelerator from 1983 until 2009, when its energy was surpassed by the Large Hadron Collider. The DØ experiment stopped taking data in 2011, when the Tevatron shut down, but data analysis is still ongoing. The DØ detector is preserved in Fermilab's DØ Assembly Building as part of a historical exhibit for public tours.
In particle physics, the parton model is a model of hadrons, such as protons and neutrons, proposed by Richard Feynman. It is useful for interpreting the cascades of radiation produced from quantum chromodynamics (QCD) processes and interactions in high-energy particle collisions.
Color-glass condensate (CGC) is a type of matter theorized to exist in atomic nuclei when they collide at near the speed of light. During such collision, one is sensitive to the gluons that have very small momenta, or more precisely a very small Bjorken scaling variable. The small momenta gluons dominate the description of the collision because their density is very large. This is because a high-momentum gluon is likely to split into smaller momentum gluons. When the gluon density becomes large enough, gluon-gluon recombination puts a limit on how large the gluon density can be. When gluon recombination balances gluon splitting, the density of gluons saturate, producing new and universal properties of hadronic matter. This state of saturated gluon matter is called the color-glass condensate.
The Roman pot is the name of a technique used in accelerator physics. Named after its implementation by the CERN-Rome collaboration in the early 1970s, it is an important tool to measure the total cross section of two particle beams in a collider. They are called pots because the detectors are housed in cylindrical vessels. The first generation of Roman pots was purpose-built by the CERN Central Workshops and used in the measurement of the total cross-section of proton-proton inter-actions in the ISR.
In particle physics phenomenology, chiral color is a speculative model which extends quantum chromodynamics (QCD), the generally accepted theory for the strong interactions of quarks. QCD is a gauge field theory based on a gauge group known as color SU(3)C with an octet of colored gluons acting as the force carriers between a triplet of colored quarks.
Quark–gluon plasma is an interacting localized assembly of quarks and gluons at thermal and chemical (abundance) equilibrium. The word plasma signals that free color charges are allowed. In a 1987 summary, Léon van Hove pointed out the equivalence of the three terms: quark gluon plasma, quark matter and a new state of matter. Since the temperature is above the Hagedorn temperature—and thus above the scale of light u,d-quark mass—the pressure exhibits the relativistic Stefan-Boltzmann format governed by temperature to the fourth power and many practically massless quark and gluon constituents. It can be said that QGP emerges to be the new phase of strongly interacting matter which manifests its physical properties in terms of nearly free dynamics of practically massless gluons and quarks. Both quarks and gluons must be present in conditions near chemical (yield) equilibrium with their colour charge open for a new state of matter to be referred to as QGP.
NA61/SHINE is a particle physics experiment at the Super Proton Synchrotron (SPS) at the European Organization for Nuclear Research (CERN). 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.
The onset of deconfinement refers to the beginning of the creation of deconfined states of strongly interacting matter produced in nucleus-nucleus collisions with increasing collision energy.
In strong interaction physics, light front holography or light front holographic QCD is an approximate version of the theory of quantum chromodynamics (QCD) which results from mapping the gauge theory of QCD to a higher-dimensional anti-de Sitter space (AdS) inspired by the AdS/CFT correspondence proposed for string theory. This procedure makes it possible to find analytic solutions in situations where strong coupling occurs, improving predictions of the masses of hadrons and their internal structure revealed by high-energy accelerator experiments. The most widely used approach to finding approximate solutions to the QCD equations, lattice QCD, has had many successful applications; however, it is a numerical approach formulated in Euclidean space rather than physical Minkowski space-time.
The 750 GeV diphoton excess in particle physics was an anomaly in data collected at the Large Hadron Collider (LHC) in 2015, which could have been an indication of a new particle or resonance. The anomaly was absent in data collected in 2016, suggesting that the diphoton excess was a statistical fluctuation. In the interval between the December 2015 and August 2016 results, the anomaly generated considerable interest in the scientific community, including about 500 theoretical studies. The hypothetical particle was denoted by the Greek letter Ϝ in the scientific literature, owing to the decay channel in which the anomaly occurred. The data, however, were always less than five standard deviations (sigma) different from that expected if there was no new particle, and, as such, the anomaly never reached the accepted level of statistical significance required to announce a discovery in particle physics. After the August 2016 results, interest in the anomaly sank as it was considered a statistical fluctuation. Indeed, a Bayesian analysis of the anomaly found that whilst data collected in 2015 constituted "substantial" evidence for the digamma on the Jeffreys scale, data collected in 2016 combined with that collected in 2015 was evidence against the digamma.
Gavin Phillip Salam, is a theoretical particle physicist and a senior research fellow at All Souls College as well as a senior member of staff at CERN in Geneva. His research investigates the strong interaction of Quantum Chromodynamics (QCD), the theory of quarks and gluons. Gavin Salam is not related to Abdus Salam.
Claude Pruneau is a Canadian-American experimental high-energy nuclear physicist. He is a professor of physics at Wayne State University and the author of several books. He is best known for his work on particle correlation measurements in heavy ion collisions at the Relativistic Heavy Ion Collider and the Large Hadron Collider.
References
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