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Jet (particle Physics)
A jet is a narrow cone of hadrons and other particles produced by the hadronization of a quark or gluon in a particle physics or heavy ion experiment. Particles carrying a color charge, such as quarks, cannot exist in free form because of quantum chromodynamics (QCD) confinement which only allows for colorless states. When an object containing color charge fragments, each fragment carries away some of the color charge. In order to obey confinement, these fragments create other colored objects around them to form colorless objects. The ensemble of these objects is called a jet, since the fragments all tend to travel in the same direction, forming a narrow "jet" of particles. Jets are measured in particle detectors and studied in order to determine the properties of the original quarks. A jet definition includes a jet algorithm and a recombination scheme. The former defines how some inputs, e.g. particles or detector objects, are grouped into jets, while the latter specifies how a mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
B-tagging
b-tagging is a method of jet flavor tagging used in modern particle physics experiments. It is the identification (or "tagging") of jets originating from bottom quarks (or b quarks, hence the name). Importance b-tagging is important because: * The physics of bottom quarks is quite interesting; in particular, it sheds light on CP violation. * Some important high-mass particles (both recently discovered and hypothetical) decay into bottom quarks. Top quarks very nearly always do so, and the Higgs boson is expected to decay into bottom quarks more than any other particle given its mass has been observed to be about 125 GeV. Identifying bottom quarks helps to identify the decays of these particles. Methods The methods for b-tagging are based on the unique features of b-jets. These include: *Hadrons containing bottom quarks have sufficient lifetime that they travel some distance before decaying. On the other hand, their lifetimes are not so high as those of light quark hadr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Event Generator
Event generators are software libraries that generate simulated high-energy particle physics events. They randomly generate events as those produced in particle accelerators, collider experiments or the early universe. Events come in different types called ''processes'' as discussed in the Automatic calculation of particle interaction or decay article. Despite the simple structure of the tree-level perturbative quantum field theory description of the collision and decay processes in an event, the observed high-energy process usually contains significant amount of modifications, like photon and gluon ''bremsstrahlung'' or loop diagram corrections, that usually are too complex to be easily evaluated in real calculations directly on the diagrammatic level. Furthermore, the non-perturbative nature of QCD bound states makes it necessary to include information that is well beyond the reach of perturbative quantum field theory, and also beyond present ability of computation in lattice QCD. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DGLAP
The Dokshitzer–Gribov–Lipatov–Altarelli–Parisi (DGLAP) evolution equations are equations in QCD describing the variation of parton distribution functions with varying energy scales. Experimentally observed scaling violation in deep inelastic scattering is important evidence for the correctness of the equations and of QCD in general. The equations were first published in the western world by Guido Altarelli and Giorgio Parisi in 1977, and so are still sometimes called the Altarelli–Parisi equations. Only later did it become known that an equivalent formula had been published in Russia by in 1977, and by Vladimir Gribov and Lev Lipatov in 1972.V. N. Gribov, L. N. Lipatov. ''Sov. J. Nucl. Phys.'' 15:438 (1972). The DGLAP QCD evolution equations are widely used in global determinations of parton distributions, like those from the CTEQ or NNPDF collaborations. See also * Jet (particle physics) * HERA * APFEL (Software) APFEL is an opensource software able to perform Do ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Giorgio Parisi
Giorgio Parisi (born 4 August 1948) is an Italian theoretical physicist, whose research has focused on quantum field theory, statistical mechanics and complex systems. His best known contributions are the QCD evolution equations for parton densities, obtained with Guido Altarelli, known as the Altarelli–Parisi or DGLAP equations, the exact solution of the Sherrington–Kirkpatrick model of spin glasses, the Kardar–Parisi–Zhang equation describing dynamic scaling of growing interfaces, and the study of whirling flocks of birds. He was awarded the 2021 Nobel Prize in Physics jointly with Klaus Hasselmann and Syukuro Manabe for groundbreaking contributions to theory of complex systems, in particular "for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales." Career Giorgio Parisi received his degree from the University of Rome La Sapienza in 1970 under the supervision of Nicola Cabibbo. He was a researcher at the L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Guido Altarelli
Guido Altarelli (12 July 1941 – 30 September 2015) was an Italian theoretical physicist. Biography Altarelli graduated in Physics from the Sapienza University of Rome in 1963 with Raoul Gatto whom he followed to the University of Florence (1965–68). He held positions at New York University (1968–69), the Rockefeller University (New York, 1969–70), the École Normale Superieure in Paris (1976–77, 81) and Boston University (1985–86). In 1970-92 he held a faculty position at the Sapienza University of Rome (full professor of theoretical physics since 1980). He was Director of the Rome Section of the INFN (1985–87). In 1992 he moved to the newly established University of Roma Tre. In 1987-2006 he was a Senior Staff Physicist at the Theory Division of CERN, and was Theory Division Leader from 2000-04. At CERN he had a leading role in the interpretation of SppS results, in the preparation of LEP and the LHC and in the theoretical analysis of the experimental results. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lev Lipatov
Lev Nikolaevich Lipatov (russian: Лев Никола́евич Липа́тов; 2 May 1940, Leningrad – 4 September 2017, Dubna) was a Russian physicist, well known for his contributions to nuclear physics and particle physics. He has been the head of Theoretical Physics Division at St. Petersburg's Nuclear Physics Institute of Russian Academy of Sciences in Gatchina and an Academician of the Russian Academy of Sciences. For the long period he worked with Vladimir Gribov, laying a basis for a field theory description of deep inelastic scattering and annihilation (Gribov-Lipatov evolution equations, later known as DGLAP, 1972). He wrote significant papers of the Pomeranchuk singularity in Quantum chromodynamics (1977) what resulted in deriving the BFKL evolution equation (Balitsky- Fadin- Kuraev-Lipatov), contributed to the study of critical phenomena (semiclassical Lipatov's approximation), the theory of tunnelling and renormalon contribution to effective couplings. He dis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vladimir Gribov
Vladimir Naumovich Gribov (Russian Влади́мир Нау́мович Гри́бов; March 25, 1930, LeningradAugust 13, 1997, Budapest) was a prominent Russian theoretical physicist, who worked on high-energy physics, quantum field theory and the Regge theory of the strong interactions. His best known contributions are the pomeron, the DGLAP equations, and the Gribov copies. Life Gribov was born in Leningrad in 1930 to a Jewish family. His father died in 1938 as a result of disease. His mother, a theater worker, not an actress, brought him up alone with his younger sister. In 1941 the family was evacuated deep into the USSR and returned in 1945. In 1947, he finished school and dreamed of becoming an actor, particularly a cinema actor. He had to accept, however, his awkwardness in such things and so chose another direction: physics. In 1947, Gribov enrolled in the Physical Faculty of Leningrad University, graduating in 1952 with diploma cum laude. Despite his ability, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parton Distribution Function
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 (a parton shower) produced from quantum chromodynamics (QCD) processes and interactions in high-energy particle collisions. Model Parton showers are simulated extensively in Monte Carlo event generators, in order to calibrate and interpret (and thus understand) processes in collider experiments. As such, the name is also used to refer to algorithms that approximate or simulate the process. Motivation The parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy hadron collisions. Any hadron (for example, a proton) can be considered as a composition of a number of point-like constituents, termed "partons". The parton model was immediately applied to electron-proton deep inelastic scattering by Bjorken and Paschos. Component particles A hadron is composed of a number of point- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parton (particle Physics)
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 (a parton shower) produced from quantum chromodynamics (QCD) processes and interactions in high-energy particle collisions. Model Parton showers are simulated extensively in Monte Carlo event generators, in order to calibrate and interpret (and thus understand) processes in collider experiments. As such, the name is also used to refer to algorithms that approximate or simulate the process. Motivation The parton model was proposed by Richard Feynman in 1969 as a way to analyze high-energy hadron collisions. Any hadron (for example, a proton) can be considered as a composition of a number of point-like constituents, termed "partons". The parton model was immediately applied to electron-proton deep inelastic scattering by Bjorken and Paschos. Component particles A hadron is composed of a number of point- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lund String Model
In particle physics, the Lund string model is a phenomenological model of hadronization. It treats all but the highest-energy gluons as field lines, which are attracted to each other due to the gluon self-interaction and so form a narrow tube (or string) of strong color field. Compared to electric or magnetic field lines, which are spread out because the carrier of the electromagnetic force, the photon, does not interact with itself. String fragmentation is one of the parton fragmentation models used in the PYTHIA/Jetset and UCLA event generators, and explains many features of hadronization quite well. In particular, the model predicts that in addition to the particle jets formed along the original paths of two separating quarks, there will be a spray of hadrons produced between the jets by the string itself—which is precisely what is observed. This use of "string" is not the same as in string theory, in which strings are the fundamental objects of nature rather tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quark Gluon Plasma
A quark () is a type of 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, the components of atomic nuclei. All commonly observable matter is composed of up quarks, down quarks and electrons. Owing to a phenomenon known as ''color confinement'', quarks are never found in isolation; they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons, or in quark–gluon plasmas. There is also the theoretical possibility of more exotic phases of quark matter. For this reason, much of what is known about quarks has been drawn from observations of hadrons. Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. They are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as ''fundamental forces'' (elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
