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Lund 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. ( Electromagnetic field lines do not stringify, but instead spread out, because the photon, carrier of the electromagnetic force, does not self-interact.) The model is named after the particle theory group of Lund University who developed it. It derived from the 1977 PhD thesis of Carsten Peterson, supervised by Bo Andersson and Gösta Gustafson. The model was refined by the contributions by researchers of the group like Torbjörn Sjöstrand, Bo Söderberg, Gunnar Ingelman, Hans-Uno Bengtsson and Ulf Pettersson. In 1979, the model was able to describe gluon jet fragmentation by considered the force field to be similar to a massless relativistic string. The model successfully predicted a specific asymmetry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the scale of protons and neutrons, while the study of combinations of protons and neutrons is called nuclear physics. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and bosons (force-carrying particles). There are three Generation (particle physics), generations of fermions, although ordinary matter is made only from the first fermion generation. The first generation consists of Up quark, up and down quarks which form protons and neutrons, and electrons and electron neutrinos. The three fundamental interactions known to be mediated by bosons are electromagnetism, the weak interaction, and the strong interaction. Quark, Quarks cannot exist on their own but form hadrons. Hadrons that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Torbjörn Sjöstrand
Torbjörn Sjöstrand (born 13 November 1954) is a Swedish theoretical physicist and a professor at Lund University in Sweden, where he also got his PhD in 1982. He is one of the main authors of PYTHIA, a program for generation of high-energy physics events. In his early career, Sjöstrand spent shorter postdoc periods at DESY (Germany) and Fermilab (USA). From 1989 to 1995 he was staff member in the CERN Theory division. Scientific contributions Sjöstrand's most enduring achievement is the Lund string model for hadronization, devised with Bengt‐Åke Andersson and others in the late 1970s and first implemented in the JETSET event generator. He later combined all the main steps of a high-energy particle collision—how quarks and gluons are first scattered, then multiply interact, and finally turn into the hadrons we detect—into one computer programme called PYTHIA. Today researchers at every major accelerator, from the old LEP and HERA rings to the Large Hadron Collider, re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
QCD String
In quantum chromodynamics (QCD), color confinement, often simply called confinement, is the phenomenon that color-charged particles (such as quarks and gluons) cannot be isolated, and therefore cannot be directly observed in normal conditions below the Hagedorn temperature of approximately 2 terakelvin (corresponding to energies of approximately 130–140 M eV per particle). Quarks and gluons must clump together to form hadrons. The two main types of hadron are the mesons (one quark, one antiquark) and the baryons (three quarks). In addition, colorless glueballs formed only of gluons are also consistent with confinement, though difficult to identify experimentally. Quarks and gluons cannot be separated from their parent hadron without producing new hadrons. Origin There is not yet an analytic proof of color confinement in any non-abelian gauge theory. The phenomenon can be understood qualitatively by noting that the force-carrying gluons of QCD have color charge, unlike t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hadron
In particle physics, a hadron is a composite subatomic particle made of two or more quarks held together by the strong nuclear force. Pronounced , the name is derived . They are analogous to molecules, which are held together by the electric force. Most of the mass of ordinary matter comes from two hadrons: the proton and the neutron, while most of the mass of the protons and neutrons is in turn due to the binding energy of their constituent quarks, due to the strong force. Hadrons are categorized into two broad families: baryons, made of an odd number of quarks (usually three) and mesons, made of an even number of quarks (usually two: one quark and one antiquark). Protons and neutrons (which make the majority of the mass of an atom) are examples of baryons; pions are an example of a meson. A tetraquark state (an exotic meson), named the Z(4430), was discovered in 2007 by the Belle Collaboration and confirmed as a resonance in 2014 by the LHCb collaboration. Two pe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quark
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 nucleus, 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 #Other_phases_of_quark_matter, 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 and extrinsic properties, intrinsic physical property, properties, including electric charge, mass, color charge, and Spin (physics), spin. They are the only elementary particles in the Standard Mode ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Particle Jet
A jet is a narrow cone of hadrons and other particles produced by the hadronization of quarks and gluons in a particle physics or heavy ion experiment. Particles carrying a color charge, i.e. quarks and gluons, cannot exist in free form because of quantum chromodynamics (QCD) confinement which only allows for colorless states. When protons collide at high energies, their color charged components each carry away some of the color charge. In accordance with confinement, these fragments create other colored objects around them to form colorless hadrons. 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 latte ... [...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] |
University Of California, Los Angeles
The University of California, Los Angeles (UCLA) is a public university, public Land-grant university, land-grant research university in Los Angeles, California, United States. Its academic roots were established in 1881 as a normal school then known as the southern branch of the California State Normal School which later evolved into San Jose State University, San José State University. The branch was transferred to the University of California to become the Southern Branch of the University of California in 1919, making it the second-oldest of the ten-campus University of California system after the University of California, Berkeley. UCLA offers 337 undergraduate and graduate degree programs in a range of disciplines, enrolling about 31,600 undergraduate and 14,300 graduate and professional students annually. It received 174,914 undergraduate applications for Fall 2022, including transfers, the most of any Higher education in the United States, university in the United Stat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PYTHIA
Pythia (; ) was the title of the high priestess of the Temple of Apollo (Delphi), Temple of Apollo at Delphi. She specifically served as its oracle and was known as the Oracle of Delphi. Her title was also historically glossed in English as the Pythoness. The Pythia was established at the latest in the 8th century BC (though some estimates date the shrine to as early as 1400 BC), and was widely credited for her prophecy, prophecies uttered under divine possession (enthusiasmos) by Apollo. The Pythian priestess emerged pre-eminent by the end of the 7th century BC and continued to be consulted until the late 4th century AD. During this period, the Delphic Oracle was the most prestigious and authoritative oracle among the Greeks, and she was among the most powerful women of the classical world. The oracle is one of the best-documented religious institutions of the classical Greeks. Authors who mention the oracle include Aeschylus, Aristotle, Clement of Alexandria, Diodorus, Diogen ... [...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. History The parton model was proposed by Richard Feynman in 1969, used originally for analysis of high-energy hadron collisions. It was applied to electron-proton deep inelastic scattering by James Bjorken and Emmanuel Anthony Paschos. Later, with the experimental observation of Bjorken scaling, the validation of the quark model, and the confirmation of asymptotic freedom in quantum chromodynamics, partons were matched to quarks and gluons. The parton model remains a justifiable approximation at high energies, and others have extended the theory over the years. Murray Gell-Mann preferred to use the term "put-ons" to refer to partons. In 1994, partons were used by Leonard Susskind to mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gunnar Ingelman
Björn Gunnar Ingelman (born 1952), is a Swedish physicist working as a professor of theoretical particle physics at Uppsala University, who is also the secretary of the Nobel Committee for Physics. Life Ingelman received his PhD in theoretical physics in 1982 at Lund University. His supervisors were Bo Andersson and Gösta Gustafson. His opponent was Frank Close. Ingelman created and leads the Theoretical High Energy Physics group at Uppsala University. Gunnar Ingelman is also a member of the Royal Swedish Academy of Sciences The Royal Swedish Academy of Sciences () is one of the Swedish Royal Academies, royal academies of Sweden. Founded on 2 June 1739, it is an independent, non-governmental scientific organization that takes special responsibility for promoting nat ... at physics class. References Swedish physicists Academic staff of Uppsala University Members of the Royal Swedish Academy of Sciences 1952 births Living people Lund University alumni Particle p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carsten Peterson
Carsten Peterson (born in 1945), is a Swedish theoretical physicist and professor at Lund University. His current field of research is computational biology. After finishing his PhD studies in theoretical physics at Lund University in 1977, Peterson worked as a postdoctoral researcher at NORDITA in Copenhagen (1978-1979) and at Stanford University (1980-1982) before returning to Lund. He has since then been active there, except for a sabbatical period (1986-1988) when he hold a Senior Scientist position at Microelectronics and Computer Technology Corporation in Austin, Texas. Peterson is a professor in theoretical physics and was elected to the Royal Swedish Academy of Sciences in 2006. Peterson's field of research was originally theoretical particle physics and statistical mechanics. In the mid 1980s he switched interests into machine learning methods, mostly artificial neural networks (ANN), for pattern recognition and image processing as well as algorithms for difficult optim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
