Quantum chromodynamics (QCD) is currently our only candidate for a theory of strong-interaction dynamics. But the evidence for it is very scanty. Indeed, QCD has only been experimentally verified in its predictions of scaling violation in deep inelastic neutrino scattering. Yet, research continues on QCD because it is based on a beautiful idea, namely the incorporation of observed particle symmetries via local gauge invariance. Nevertheless QCD, a quantum field theory in 3 + 1 dimensions is still without solution. The sheer difficulty in solving the full quantum problem has led some to various approximations, in the hopes of shedding light on the structure of the theory. (orig./FKS)
These proceedings mark the fourth workshop on Quantum Chromodynamics held at the American University of Paris during the week of 1-6 june 1998. 8 half-day sessions, each dealing with a distinct theme within the general QCD framework. The different topics treated are: 1) diffractive production and the pomeron, 2) high energy scattering and the pomeron, 3) thermal and other fluctuations, 4) hadrons physics, 5) strings, branes and duality, 6) conventional and unconventional QCD, 7) media effects in scattering, 7) media effects, statistics and spin correlations in QCD, 8) lattice methods, 9) lattice methods and QCD theory, and 10) new and gauge-invariant methods in QCD/Quantum field theory
Complementarity in Wormhole Chromodynamics
Lo, Hoi-Kwong; Lee, Kai-Ming; Preskill, John
1993-01-01
The electric charge of a wormhole mouth and the magnetic flux ``linked'' by the wormhole are non-commuting observables, and so cannot be simultaneously diagonalized. We use this observation to resolve some puzzles in wormhole electrodynamics and chromodynamics. Specifically, we analyze the color electric field that results when a colored object traverses a wormhole, and we discuss the measurement of the wormhole charge and flux using Aharonov-Bohm interference effects. We suggest that wormhol...
Elements of quantum chromodynamics
Bjorken, J.D.
1979-01-01
The subject of quantum chromodynamics is discussed at length. The introduction motivates the exposition and points out the analogies between QCD and QED. Then, after some assumptions about the nature of QCD, a description is given of what the solution of the theory should look like for three stages of complexity: pure QCD with no fermions or other sources, introduction of superheavy quarks, introduction of the light quarks (u, d, s) with vacuum polarization and pair creation. Next, canonical quantization of QCD by use of a Hamiltonian formulation (in A/sub 0/ = 0 gauge) is considered; gauge ambiguities, theta vacua, instantons, etc., are encountered. Then the properties of the three stages noted above are discussed in much greater detail. These follow descriptions of the confinement problem and various approaches to it, as well as of more radical alternatives to QCD, such as the string model or the Pati-Salam program. Included in the summary is an assessment of the current situation. 101 references, 23 figures, 2 tables. (RWR)
Elements of quantum chromodynamics
The subject of quantum chromodynamics is discussed at length. The introduction motivates the exposition and points out the analogies between QCD and QED. Then, after some assumptions about the nature of QCD, a description is given of what the solution of the theory should look like for three stages of complexity: pure QCD with no fermions or other sources, introduction of superheavy quarks, introduction of the light quarks (u, d, s) with vacuum polarization and pair creation. Next, canonical quantization of QCD by use of a Hamiltonian formulation (in A0 = 0 gauge) is considered; gauge ambiguities, theta vacua, instantons, etc., are encountered. Then the properties of the three stages noted above are discussed in much greater detail. These follow descriptions of the confinement problem and various approaches to it, as well as of more radical alternatives to QCD, such as the string model or the Pati-Salam program. Included in the summary is an assessment of the current situation. 101 references, 23 figures, 2 tables
Quantum chromodynamics and collider processes
These lectures notes on quantum chromodynamics aim at reviewing the status of today's theoretical description of Standard Model processes relevant for Tevatron and Large Hadron Collider analyses, and of the tools that are used in phenomenological studies. A few recent ideas to further refine our abilities to perform technically challenging calculations are also presented. (author)
Quantum Entanglement and Quantum Chromodynamics
Abbas, Afsar
2000-01-01
Non-locality or entanglement is an experimentally well established property of quantum mechanics. Here we study the role of quantum entanglement for higher symmetry group like $ SU(3_c) $, the gauge group of quantum chromodynamics (QCD). We show that the hitherto unexplained property of confinement in QCD arises as a fundamental feature of quantum entanglement in $ SU(3_c) $.
Quantum Chromodynamic at finite temperature
A formal expression to the Gibbs free energy of topological defects of quantum chromodynamics (QCD)by using the semiclassical approach in the context of field theory at finite temperature and in the high temperature limit is determined. This expression is used to calculate the free energy of magnetic monopoles. Applying the obtained results to a method in which the free energy of topological defects of a theory may indicate its different phases, its searched for informations about phases of QCD. (author)
New perspectives in quantum chromodynamics
In these lectures I will discuss three central topics in quantum chromodynamics: (1) the use of light cone quantization and Fock space methods to determine the long and short-distance structure of quark and gluon distributions within hadrons; (2) the role of spin, heavy quarks, and nuclei in unraveling fundamental phenomenological features of QCD; and (3) a new approach to understanding the scale and scheme dependence of perturbative QCD predictions
Quantum chromodynamics and hadron jets
These lectures are devoted to the description of the various properties of hard scattering processes with the participation of hadrons in the framework of Quantum Chromodynamics. We discuss in detail the validity and region of applicability of perturbation theory applied to hadron processes. Particular attention is paid to the question of the structure of quark and gluon jets produced in hard processes (as an example, e+ e- annihilation into hadrons). In addition to giving a pedagogical review, we also present new results. (orig.)
Light-front quantum chromodynamics
An outstanding goal of physics is to find solutions that describe hadrons in the theory of strong interactions, Quantum Chromodynamics (QCD). For this goal, the light-front Hamiltonian formulation of QCD (LFQCD) is a complementary approach to the well-established lattice gauge method. LFQCD offers access to the hadrons' nonperturbative quark and gluon amplitudes, which are directly testable in experiments at existing and future facilities. We present an overview of the promises and challenges of LFQCD in the context of unsolved issues in QCD that require broadened and accelerated investigation. We identify specific goals of this approach and address its quantifiable uncertainties
Quantum chromodynamics: achievements and unresolved problems
Modern status of quantum chromodynamics (QCD) is reviewed. Achievements of QCD: establishment of the form of QCD lagrangian, asymptotic freedom, noticeable progress in description of statical properties of mesons and baryons and low-energy processes based on chromodynamics, are reviewed. The unsolved problems: confinement, chiral symmetry, quarkonium, exotic states and hadron substance at high temperatures and densities are mentioned
Numerical simulations in quantum chromodynamics
One of the most outstanding challenges in physics today is to explain quantitatively the observed properties of protons, neutrons etc. generically called hadrons. A significant part of this challenge is also to explain so called Quark Confinement. Though there is very strong evidence that the correct theoretical description is provided by the so called Quantum Chromodynamics (QCD), it is an extremely difficult theory to solve by traditional analytical techniques. Great strides have been made over the last couple of decades in numerical simulations of this theory which require the fastest available supercomputers. In this paper I shall briefly describe QCD and also describe its numerical simulations and their complexity. I shall briefly describe the most recent results obtained on the Teraflop Linux cluster KABRU at IMSc. (author)
Multiparticle production and quantum chromodynamics
Dremin, I M
2002-01-01
The theory of strong interactions, quantum chromodynamics (QCD), is quite successful in the prediction and description of main features of multiparticle production processes at high energies. The general perturbative QCD approach to these processes (mainly to e+e- -annihilation) is briefly formulated and its problems are discussed. It is shown that the analytical calculations at the parton level with the low-momentum cut-off reproduce experimental data on the hadronic final state in multiparticle production processes at high energies surprisingly accurately even though the perturbative expansion parameter is not very small. Moreover, it is important that the perturbative QCD has been able not only to describe the existing data but also to predict many bright qualitatively new phenomena.
Relativistic nuclear physics and quantum chromodynamics. Abstracts
The data of investigations on problems of high energy physics are given. Special attention pays to quantum chromodynamics at large distances, cumulative processes, multiquark states and relativistic nuclear collisions
Quantum chromodynamics at large distances
The properties of quantum chromodynamics (QCD)at large distances are considered in the framework of traditional quantum field theory. The parameters that determine the infrared region are determined self-consistently by means of the renormalization-group method. Recent studies that confirm a singular infrared asymptotic behavior M2 /(k2 )2 of the gluon propagator are reviewed. Solutions of the Schwinger--Dyson equation for the quark propagator are found with the necessary properties: spontaneous breaking of the chiral invariance and a nonperturbative nature. The infrared behaviors of the lowest Green's functions are used to calculate the vacuum expectation values of the gluon and quark fields. Good agreement between the calculated vacuum expectation values and their phenomenological values is obtained. The study of the behavior of QCD at large distances leads to the conclusion that at the present level of development of the theory two possibilities can be discussed. The first is the well-known confinement hypothesis; the second has been called incomplete confinement and necessarily implies that open color can be observed. It is shown that the second possibility does not contradict existing experiments. Experimental data on anomalous nuclear fragments and ultra-high-energy radiation from the galactic source Cygnus X-3 are considered as evidence for incomplete confinement. The importance of searches for states with open color is emphasized
Multibody quark forces in quantum chromodynamics
A general exposition of multibody quark forces in quantum chromodynamics is given. The low-energy Hamiltonian involves two-, three-, and four-body quark potentials. We compute the short-range three- and four-body potentials to lowest-order terms in v/c and show that the former does not contribute to the mass of baryons
Jet angular distribution from quantum chromodynamics
The quantum chromodynamic correction to jet (defined a la Sterman and Weinberg) angular distribution in energetic e+e- annihilation is calculated to order α/sub s/ keeping exact dependence on epsilon and delta. Deviations from the zeroth order distribution, 1 + cos2theta, for are found relatively large values of epsilon and delta. This effect could be tested at the existing e+e- colliding beam facilities
Color-charge algebras in Adler's chromodynamics
We show that the color-charge algebra in the three-quark sector generated by the matrices of the fundamental representation of U(n) does not have the trace properties required in Adler's extension of chromodynamics. We also discuss a diagrammatic representation of algebras generated by quark and antiquark charges in general, and an embedding of the N-quark algebra in the symmetric group S/sub N/+1
Conference summary: Quantum chromodynamics at small x
The range of electroproduction kinematics xBj = Q2/(2p · q) ≥ 10-4 at Q2 ≥ 10 GeV2 accessible at the HERA e - p collider will provide a challenging high energy testing ground for quantum chromodynamics in a regime where the gluon distribution of the proton is expected to saturate and new types of multi-scattering higher twist contributions to structure functions become important. In this summary I give a brief overview of the recent theoretical work presented at the Hamburg conference. 19 refs., 2 figs
Quantum chromodynamics and the dynamics of hadrons
The application of perturbative quantum chromodynamics to the dynamics of hadrons at short distance is reviewed, with particular emphasis on the role of the hadronic bound state. A number of new applications are discussed, including the modification to QCD scaling violations in structure functions due to hadronic binding; a discussion of coherence and binding corrections to the gluon and sea-quark distributions; QCD radiative corrections to dimensional counting rules for exclusive processes and hadronic form factors at large momentum transfer; generalized counting rules for inclusive processes; the special role of photon-induced reactions in QCD, especially applications to jet production in photon-photon collisions, and photon production at large transverse momentum. Also presented is a short review of the central problems in large P/sub T/ hadronic reactions and the distinguishing characteristics of gluon and quark jets. 163 references
Random Matrix Theory and Quantum Chromodynamics
Akemann, Gernot
2016-01-01
These notes are based on the lectures delivered at the Les Houches Summer School in July 2015. They are addressed at a mixed audience of physicists and mathematicians with some basic working knowledge of random matrix theory. The first part is devoted to the solution of the chiral Gaussian Unitary Ensemble in the presence of characteristic polynomials, using orthogonal polynomial techniques. This includes all eigenvalue density correlation functions, smallest eigenvalue distributions and their microscopic limit at the origin. These quantities are relevant for the description of the Dirac operator spectrum in Quantum Chromodynamics with three colours in four Euclidean space-time dimensions. In the second part these two theories are related based on symmetries, and the random matrix approximation is explained. In the last part recent developments are covered including the effect of finite chemical potential and finite space-time lattice spacing, and their corresponding orthogonal polynomials. We also give some ...
Novel nuclear phenomena in quantum chromodynamics
Many of the key issues in understanding quantum chromodynamics involve processes in nuclear targets at intermediate energies. A range of hadronic and nuclear phenomena-exclusive processes, color transparency, hidden color degrees of freedom in nuclei, reduced nuclear amplitudes, jet coalescence, formation zone effects, hadron helicity selection rules, spin correlations, higher twist effects, and nuclear diffraction were discussed as tools for probing hadron structure and the propagation of quark and gluon jets in nuclei. Several areas were also reviewed where there has been significant theoretical progress determining the form of hadron and nuclear wave functions, including QCD sum rules, lattice gauge theory, and discretized light-cone quantization. A possible interpretation was also discussed of the large spin correlation A/sub NN/ in proton-proton scattering, and how relate this effect to an energy and angular dependence of color transparency in nuclei. 76 refs., 24 figs
Nuclear Physics from Lattice Quantum Chromodynamics
Savage, Martin J
2015-01-01
Quantum Chromodynamics and Quantum Electrodynamics, both renormalizable quantum field theories with a small number of precisely constrained input parameters, dominate the dynamics of the quarks and gluons - the underlying building blocks of protons, neutrons, and nuclei. While the analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they encounter difficulties when applied to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the exascale during the next decade will provide the ability to determine a range of important strong interaction processes directly from QCD using the numerical technique of Lattice QCD. This will complement the nuclear physics experimental program, and in partnership with new thrusts in nuclear many-body theory, will enable unprecedented understanding and refinement of nuclear forces and, more generally, the visible matter in our universe. In th...
Novel nuclear phenomena in quantum chromodynamics
Brodsky, S.J.
1987-08-01
Many of the key issues in understanding quantum chromodynamics involve processes in nuclear targets at intermediate energies. A range of hadronic and nuclear phenomena-exclusive processes, color transparency, hidden color degrees of freedom in nuclei, reduced nuclear amplitudes, jet coalescence, formation zone effects, hadron helicity selection rules, spin correlations, higher twist effects, and nuclear diffraction were discussed as tools for probing hadron structure and the propagation of quark and gluon jets in nuclei. Several areas were also reviewed where there has been significant theoretical progress determining the form of hadron and nuclear wave functions, including QCD sum rules, lattice gauge theory, and discretized light-cone quantization. A possible interpretation was also discussed of the large spin correlation A/sub NN/ in proton-proton scattering, and how relate this effect to an energy and angular dependence of color transparency in nuclei. 76 refs., 24 figs.
Calculation of baryon masses in quantum chromodynamics
The polarization operator of quark currents with the baryon quantum numbers is considered in quantum chromodynamics. The non-zero mean vacuum of the field operator products are taken into account. The sum rules are obtained assuming that in the virtuality region approximately 1 GeV, among the mean vacuum values violating the chiral invariance, the most important is . Saturating these sum rules by the lowest baryonic states one is able to calculate the masses of the isobar Δ and nucleon N, Msub(Δ) 1.4 GeV, Msub(N) = 1 GeV, up to 15 % through the known value . The mass splitting in the baryonic decuplet Msub(Σ*) - Msub(Δ) = 125 MeV is calculated in the first order in the current strange quark mass msub(s) = 150 MeV. Certain results for that baryonic resonances have been obtained
Hadronic and nuclear phenomena in quantum chromodynamics
Many of the key issues in understanding quantum chromodynamics involves processes at intermediate energies. We discuss a range of hadronic and nuclear phenomena - exclusive processes, color transparency, hidden color degrees of freedom in nuclei, reduced nuclear amplitudes, jet coalescence, formation zone effects, hadron helicity selection rules, spin correlations, higher twist effects, and nuclear diffraction - as tools for probing hadron structure and the propagation of quark and gluon jets in nuclei. Many of these processes can be studied in electroproduction, utilizing internal targets in storage rings. We also review several areas where there has been significant theoretical progress in determining the form of hadron and nuclear wavefunctions, including QCD sum rules, lattice gauge theory, and discretized light-cone quantization. 98 refs., 40 figs., 2 tabs
Massive quark polarization in Quantum Chromodynamics subprocesses
It is well known that the single polarization asymmetries are large in hyperon production in contrast with naive Quantum Chromodynamics predictions. We have explored the possibility of polarization of quarks in QCD subprocesses, assuming that the quark mass can be significant at energies of interest. The fourth order contribution to the single spin asymmetry in each important subprocess for strange quark production is calculated. Mass dependence and the kinematical properties of the polarization of the strange quark in the partons' center-of-mass frame are discussed. The s-quark polarization in the hadrons' center-of-mass frame is obtained by performing the convolution integrations with the initial state parton distribution functions. A fit to the hyperon polarization is presented that reproduces the unique and striking kinematic dependence of the data. This is evidence that the ''seed'' of the polarization is in the basic scattering process and it is dominated by the gluon fusion subprocess. 31 figs
Underlying theory based on quaternions for Alder's algebraic chromodynamics
It is shown that the complex-linear tensor product for quantum quaternionic Hilbert (module) spaces provides an algebraic structure for the non-local gauge field in Adler's algebraic chromodynamics for U
Hadron masses in quantum chromodynamics on the transverse lattice
Calculational methods are formulated for the transverse lattice version of quantum chromodynamics. These methods are used to study the low lying spectrum of gluon bound states in the pure Yang-Mills theory. 15 references
National software infrastructure for lattice quantum chromodynamics
Brower, R C; DeTar, C E; Edwards, R G; Holmgren, Donald J; Mawhinney, R D; Watson, W; Zhang, Y
2006-06-01
Quantum chromodynamics (QCD) is the widely accepted theory of the strong interactions of quarks and gluons. Only through large scale numerical simulation has it been possible to work out the predictions of this theory for a vast range of phenomena relevant to the US Department of Energy experimental program. Such simulations are essential to support the discovery of new phenomena and more fundamental interactions. With support from SciDAC the USQCD collaboration has developed software and prototyped custom computer hardware to carry out the required numerical simulations. We have developed a robust, portable data-parallel code suite. It provides a user-friendly basis for writing physics application codes for carrying out the calculations needed to predict the phenomenology of QCD. We are using this efficient and optimized code base to develop new physics application code, to improve the performance of legacy code, and to construct higher level tools, such as QCD-specific sparse matrix solvers. We give a brief overview of the design of the data parallel API and its various components. We describe performance gains achieved in the past year. Finally, we present plans for further improvements under SciDAC-2.
Functional renormalization group methods in quantum chromodynamics
Braun, J.
2006-12-18
We apply functional Renormalization Group methods to Quantum Chromodynamics (QCD). First we calculate the mass shift for the pion in a finite volume in the framework of the quark-meson model. In particular, we investigate the importance of quark effects. As in lattice gauge theory, we find that the choice of quark boundary conditions has a noticeable effect on the pion mass shift in small volumes. A comparison of our results to chiral perturbation theory and lattice QCD suggests that lattice QCD has not yet reached volume sizes for which chiral perturbation theory can be applied to extrapolate lattice results for low-energy observables. Phase transitions in QCD at finite temperature and density are currently very actively researched. We study the chiral phase transition at finite temperature with two approaches. First, we compute the phase transition temperature in infinite and in finite volume with the quark-meson model. Though qualitatively correct, our results suggest that the model does not describe the dynamics of QCD near the finite-temperature phase boundary accurately. Second, we study the approach to chiral symmetry breaking in terms of quarks and gluons. We compute the running QCD coupling for all temperatures and scales. We use this result to determine quantitatively the phase boundary in the plane of temperature and number of quark flavors and find good agreement with lattice results. (orig.)
Effective action approach to quantum chromodynamics
Though the Lagrangian of quantum chromodynamics is well known, it has proven extremely difficult to derive precisely all its consequences to compare with experiment. Approximations based on physical reasoning must be made. One method is to calculate the effective action for some particularly simple configuration of gluons and use this to analyze an arbitrary system of interacting quarks. In the first chapter, the one-loop correction to the gluon propagator is computed in two different ways - dimensional regularization and Schwinger's proper time method. The renormalization mass parameters appearing in the two treatments can then be related and the exact one-loop effective action of a constant gluon field can be expressed in terms of the experimentally determinable Λ/sub MS/. In the following chapter, the interaction of a heavy quark-antiquark pair governed by this action is considered and it is shown how the spectrum, and, in particular, the spin splittings of the bound states can be found. Due to asymptotic freedom, a massive quarkonium is analogous to a non-relativistic electromagnetic system. At short distances, the results are the same as those derived from perturbation theory though, for example, the hyperfine structure arises in a different way. At large distances, the analysis is qualitative but our results agree with the predictions of strong coupling lattice gauge theories
Functional renormalization group methods in quantum chromodynamics
We apply functional Renormalization Group methods to Quantum Chromodynamics (QCD). First we calculate the mass shift for the pion in a finite volume in the framework of the quark-meson model. In particular, we investigate the importance of quark effects. As in lattice gauge theory, we find that the choice of quark boundary conditions has a noticeable effect on the pion mass shift in small volumes. A comparison of our results to chiral perturbation theory and lattice QCD suggests that lattice QCD has not yet reached volume sizes for which chiral perturbation theory can be applied to extrapolate lattice results for low-energy observables. Phase transitions in QCD at finite temperature and density are currently very actively researched. We study the chiral phase transition at finite temperature with two approaches. First, we compute the phase transition temperature in infinite and in finite volume with the quark-meson model. Though qualitatively correct, our results suggest that the model does not describe the dynamics of QCD near the finite-temperature phase boundary accurately. Second, we study the approach to chiral symmetry breaking in terms of quarks and gluons. We compute the running QCD coupling for all temperatures and scales. We use this result to determine quantitatively the phase boundary in the plane of temperature and number of quark flavors and find good agreement with lattice results. (orig.)
Simple model of the ground state of quantum chromodynamics
A proposal for the form of the ground-state wave function of quantum chromodynamics is made. It is shown to lead to the phenomenology of the MIT Bag Model. The parameters of this model are related to the fundamental scale parameter of QCD. 2 tables
U matrix construction for Quantum Chromodynamics through Dirac brackets
A procedure for obtaining the U matrix using Dirac brackets, recently developed by Kiefer and Rothe, is applied for Quantum Chromodynamics. The correspondent interaction Lagrangian is the same obtained by Schwinger, Christ and Lee, using independent methods. (L.C.J.A.)
Tetraquark mesons in large-N quantum chromodynamics.
Weinberg, Steven
2013-06-28
It is argued that exotic mesons consisting of two quarks and two antiquarks are not ruled out in quantum chromodynamics with a large number N of colors, as generally thought. Tetraquarks of one class are typically long-lived, with decay rates proportional to 1/N. PMID:23848862
Quantum Chromodynamics and Nuclear Physics at Extreme Energy Density
The report describes research in theoretical quantum chromodynamics, including effective field theories of hadronic interactions, properties of strongly interacting matter at extreme energy density, phenomenology of relativistic heavy ion collisions, and algorithms and numerical simulations of lattice gauge theory and other many-body systems.
Predictions of quantum chromodynamics of the second order
The model of partons is generalized. Proof of factorization in the region of the large moments of transfer, higher-order corrections in a scalar theory, in non-abelian gauge theories, for single transitions, higher-order effects for structure and fragmentation functions in quantum chromodynamics, analytical solution in the space of the X's are presented
Quantum Chromodynamics and Nuclear Physics at Extreme Energy Density
Mueller, B.; Bass, S.A.; Chandrasekharan, S.; Mehen, T.; Springer, R.P.
2005-11-07
The report describes research in theoretical quantum chromodynamics, including effective field theories of hadronic interactions, properties of strongly interacting matter at extreme energy density, phenomenology of relativistic heavy ion collisions, and algorithms and numerical simulations of lattice gauge theory and other many-body systems.
Quantum chromodynamics effects in electroweak and Higgs physics
Frank Petriello
2012-10-01
Several examples of the often intricate effects of higher-order quantum chromodynamics (QCD) corrections on predictions for hadron-collider observables, are discussed, using the production of electroweak gauge boson and the Standard Model Higgs boson as examples. Particular attention is given to the interplay of QCD effects and experimental cuts, and to the use of scale variations as estimates of theoretical uncertainties.
Large-psub(T) hadron correlations in quantum chromodynamics
The quantum chromodynamics approach to large-transverse-momentum inclusive hadron production is extended to two-hadron correlations. Comparison with data on transverse momentum sharing distributions is presented and the scale violating effects of the parton fragmentation functions are discussed. Opposite-side rapidity distributions are in fair agreement with data and show a weak back-to-back effect. The importance of calculating the ''hard'' component of output momentum (acoplanarity) is underlined. (author)
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
Shebeko, Alexander
2016-03-01
The notion of clothing in quantum field theory (QFT), put forward by Greenberg and Schweber and developed by M. Shirokov, is applied in quantum electrodynamics (QED) and quantum chromodynamics (QCD). Along the guideline we have derived a novel analytic expression for the QED Hamiltonian in the clothed particle representation (CPR). In addition, we are trying to realize this notion in QCD (to be definite for the gauge group SU(3)) when drawing parallels between QCD and QED.
Nuclear chromodynamics is not the colorization of nuclear physics
The successful description of nuclei in terms of nucleons, deltas and mesons provides an enormous challenge to QCD. It compels us to pursue our theoretical understanding of chromodynamics into the realm of multiple color singlets in order to examine the concept of color saturation. To pursue this theme, we examine the idea of nuclear transparency in the light of models for confinement and describe the formulation of lattice simulations sensitive to exchange forces. 22 refs., 7 figs
Automated Code Generation for Lattice Quantum Chromodynamics and beyond
Barthou, Denis; Dolbeau, Romain; Grosdidier, Gilbert; Eisenbeis, Christina; Kruse, Michael; Pene, Olivier; Petrov, Konstantin; Tadonki, Claude
2014-01-01
We present here our ongoing work on a Domain Specific Language which aims to simplify Monte-Carlo simulations and measurements in the domain of Lattice Quantum Chromodynamics. The tool-chain, called Qiral, is used to produce high-performance OpenMP C code from LaTeX sources. We discuss conceptual issues and details of implementation and optimization. The comparison of the performance of the generated code to the well-established simulation software is also made.
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
Shebeko Alexander
2016-01-01
Full Text Available The notion of clothing in quantum field theory (QFT, put forward by Greenberg and Schweber and developed by M. Shirokov, is applied in quantum electrodynamics (QED and quantum chromodynamics (QCD. Along the guideline we have derived a novel analytic expression for the QED Hamiltonian in the clothed particle representation (CPR. In addition, we are trying to realize this notion in QCD (to be definite for the gauge group SU(3 when drawing parallels between QCD and QED.
Progress toward the effective Quantum Chromodynamic Lagrangian from symmetry considerations
Salomone, A.N.
1982-01-01
The properties of an effective Lagrangian which satisfies both the axial and trace anomaly equations of Quantum Chromodynamics are investigated both from the theoretical and phenomenological points of view. The model Lagrangian requires that chiral symmetry be broken spontaneously. The non-linear approximation of the model illuminates eta-glue duality or mixing. The phase transition behavior of the model of Quantum Chromodynamics can be studied as the numbers of flavors and the vacuum angle are varied by analyzing a simple mechanical analog. The analog of the model is similar to the massive Schwinger model. The possibility of a physical scalar glue state is discussed and it is shown that it is characterized by a pronounced eta to two glue decay width. A nonperturbative Quantum Chromodynamic vacuum is seen to follow directly from satisfying the trace anomaly. The quark matter meson, eta, is at least as prominent as the glueball, iota, in the gluon dominated reaction psi to gamma plus anything. An associated large breaking of flavor SU(3) is shown to be ameliorated as the model is made more realistic by lowering scalar meson masses from infinity. The pi delta decay of the iota (1440) can be reasonably well estimated without the need of introducing any new parameters.
Foundations of quantum chromodynamics: Perturbative methods in gauge theories
This volume develops the techniques of perturbative QCD in great detail starting with field theory. Aside from extensive treatments of the renormalization group technique, the operator product expansion formalism and their applications to short-distance reactions, this book provides a comprehensive introduction to gauge field theories. Examples and exercises are provided to amplify the discussions on important topics. Contents: Introduction; Elements of Quantum Chromodynamics; The Renormalization Group Method; Asymptotic Freedom; Operator Product Expansion Formalism; Applications; Renormalization Scheme Dependence; Factorization Theorem; Further Applications; Power Corrections; Infrared Problem. Power Correlations; Infrared Problem
Quantum chromodynamics: A theory of the nuclear force
A brief outline is given of a possible theory of the nuclear force and the strong interactions between elementary particles, which is supposed responsible for nuclear matter. The theory is known as quantum chromodynamics because of its association with a new kind of nuclear charge called colour and its resemblance to quantum electrodynamics. Early ideas on the nuclear force and the emergence of the quark model and the QCD Lagrangian are described first. Then properties of this theory and the problem of quark confinement, the perturbative phase of QCD, and the non-perturbative or confinement phase of QCD and the description of hadrons and their interactions are discussed
Local gauge symmetry and confinement in quantum chromodynamics
The nonabelian color gauge theory of quarks and gluons has been proposed as the basis for fundamental theory of hadrons. The features of this theory (quantum chromodynamics) are considered which lead to confinement. A transverse lattice formulation of the theory is also discussed, which is used as a basis for calculation of properties of the hadron bound states. The theory is quantized by eliminating the longitudinal degrees of freedom in favour of coulomb potential. Hadrons are formed as bound states of quarks and the symmetric phase gluons
Hadronic correlations in quantum chromodynamics on the lattice
The quantum chromodynamics (QCD), the quantum field theory of strong interactions cannot be solved in the case of small momentum transfer by the usual perturbative methods. To this non-perturbative regime belong especially bound matter states, hadrons. A procedure for the calculation of their properties directly from the fundamental fields of QCD is the numerical evaluation of euclidean path integrals in discretized space-time. For this QCD is formulated as lattice gauge theory. In the present study the author presents an extensive didactical look into this methodics and explains the concrete realization by means of the calculation of hadronic correlations
Study of some exclusive hard reactions in Quantum Chromodynamics
This research thesis addresses some phenomenological aspects of exclusive hard reactions which do not appear in the null distance formulation. The first part of this report is an introduction to the study of high impulse transfer processes by using perturbative quantum chromodynamics. It briefly presents basic elements of perturbative quantum chromodynamics (Feynman rules, calculation of an observable, UV and IR regimes), presents the formalism appropriate to the study of exclusive hard reactions with a specific attention to the formulation of counting rules and to the calculation of the simplest observable, i.e. the pion form factor. The second part addresses the study of form factors of hadrons in the time region. The author outlines the difficulty for the formalism to report the noticed difference when passing from the time region to the space region, and shows how it is possible to theoretically report the observation. A published article is then provided (Timelike form factor at high energy). The third part tackles the issue of violation of the helicity conservation rule. The origin of this rule of conservation is recalled, and its experimental status is discussed. As far as elastic collisions between hadrons are concerned, the author proposes a scenario to explain noticed violations, as well as the necessary formalism for their quantitative study. Another published article is provided: 'Hadron helicity violation in exclusive processes: quantitative calculations in leading order QCD'
Strong interactions and quantum chromodynamics at the leading logarithm approximation
This thesis is a contribution to the study of Quantum Chromodynamics (QCD) at the leading logarithm approximation (LLA). We have used the interpretation of the LLA in terms of the generalized parton model to propose tests of elementary processes of QCD in large transverse momentum photoproduction reactions. We have used the LLA to sum gluon radiation effects induced in high energy hadronic reactions. We have obtained this way a rise of the nucleon-nucleon total cross section of 15 mb from 60 GeV to 540 GeV. We have exploited the existence of a preconfinement transition in the LLA to study scaling violations in the framework of the dual parton model
Chiral Relaxation Time at the Chiral Crossover of Quantum Chromodynamics
Ruggieri, M; Chernodub, M
2016-01-01
We study microscopic processes responsible for chirality flips in the thermal bath of Quantum Chromodynamics at finite temperature and zero baryon chemical potential. We focus on the temperature range where the crossover from chirally broken phase to quark-gluon plasma takes place, namely $T \\simeq (150, 200)$ MeV. The processes we consider are quark-quark scatterings mediated by collective excitations with the quantum number of pions and $\\sigma$-meson, hence we refer to these processes simply as \\sugg{to} one-pion (one-$\\sigma$) exchange\\sugg{s}. We use a Nambu-Jona-Lasinio model to compute equilibrium properties of the thermal bath, as well as the relevant scattering kernel to be used in the collision integral to estimate the chiral relaxation time $\\tau$. We find $\\tau\\simeq 0.1 \\div 1$ fm/c around the chiral crossover.
Resolution issues of nucleon spin in quantum chromodynamics
Lively discussions have been exchanged around the question whether it was possible to completely resolve nucleon spin to the contribution of the intrinsic spin of quarks/gluons and orbital angular momentum, without a contradiction to the color gauge invariance of quantum chromodynamics. This paper firstly showed what performs an essential role in the resolution issues of gauge invariance of nucleon spin, especially in its uniqueness issues, is the invariance toward Lorentz boost in the direction of the momentum of nucleon. What plays a crucial role in the resolution issues of nucleon spin is Lorentz symmetry, and gauge symmetry plays only a minor role. This paper next compared the advantages of two nucleon spin resolutions that are physically non-equivalent, namely, the resolution of canonical. (A.O.)
Some views about chromodynamics; Quelques elements de chromodynamique
Pilon, E. [Ecole Nationale Superieure Agronomique, 31 - Toulouse (France)]|[Ecole Nationale Superieure, LAPP, 74 - Annecy-le-Vieux (France)
1995-12-31
The first lesson recalls some basis of quantum chromodynamics (QCD). Particularly the Lagrangian density and the Feynman laws are described. The second lesson presents the problem of renormalization and the notion of efficient coupling. The important property of asymptotic freedom of QCD is detailed. The third lesson gives a schematic classification of processes involved in hadronic physics with high energy-momentum transfer. Scale invariance and its breakdown by using leading log method is presented and leads to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equations. The fourth and last lesson paves the way to use the factorization method beyond the leading logs in the case of hadron-hadron collision within the frame of leading twist. Some ideas about comparisons between semi-analytical calculations and Monte-Carlo simulations are given. (A.C.) 55 refs.
Least-squares finite element methods for quantum chromodynamics
Ketelsen, Christian [Los Alamos National Laboratory; Brannick, J [PENN STATE UNIV; Manteuffel, T [UNIV OF CO.; Mccormick, S [UNIV OF CO.
2008-01-01
A significant amount of the computational time in large Monte Carlo simulations of lattice quantum chromodynamics (QCD) is spent inverting the discrete Dirac operator. Unfortunately, traditional covariant finite difference discretizations of the Dirac operator present serious challenges for standard iterative methods. For interesting physical parameters, the discretized operator is large and ill-conditioned, and has random coefficients. More recently, adaptive algebraic multigrid (AMG) methods have been shown to be effective preconditioners for Wilson's discretization of the Dirac equation. This paper presents an alternate discretization of the Dirac operator based on least-squares finite elements. The discretization is systematically developed and physical properties of the resulting matrix system are discussed. Finally, numerical experiments are presented that demonstrate the effectiveness of adaptive smoothed aggregation ({alpha}SA ) multigrid as a preconditioner for the discrete field equations resulting from applying the proposed least-squares FE formulation to a simplified test problem, the 2d Schwinger model of quantum electrodynamics.
Quantum chromodynamics at high energy and statistical physics
Munier, S
2009-01-01
When hadrons are scattered at high energies, strong color fields, whose dynamics is described by quantum chromodynamics (QCD), are generated at the interaction point. If one represents these fields in terms of partons (quarks and gluons), the average number densities of the latter saturate at ultrahigh energies. At that point, nonlinear effects become predominant in the dynamical equations. The hadronic states that one gets in this regime of QCD are generically called ``color glass condensates''. Our understanding of scattering in QCD has benefited from recent progress in statistical and mathematical physics. The evolution of hadronic scattering amplitudes at fixed impact parameter in the regime where nonlinear parton saturation effects become sizable was shown to be similar to the time evolution of a system of classical particles undergoing reaction-diffusion processes. The dynamics of such a system is essentially governed by equations in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-P...
Quantum chromodynamics at high energy and noisy traveling waves
Munier, S
2012-01-01
When hadrons scatter at high energies, strong color fields, whose dynamics is described by quantum chromodynamics (QCD), are generated at the interaction point. If one represents these fields in terms of partons (quarks and gluons), the average number densities of the latter saturate at ultrahigh energies. At that point, nonlinear effects become predominant in the dynamical equations. The hadronic states that one gets in this regime of QCD are generically called "color glass condensates". Our understanding of scattering in QCD has benefited from recent progress in statistical and mathematical physics. The evolution of hadronic scattering amplitudes at fixed impact parameter in the regime where nonlinear parton saturation effects become sizable was shown to be similar to the time evolution of a system of classical particles undergoing reaction-diffusion processes. The dynamics of such a system is essentially governed by equations in the universality class of the stochastic Fisher-Kolmogorov-Petrovsky-Piscounov...
The CT14 Global Analysis of Quantum Chromodynamics
Dulat, Sayipjamal; Gao, Jun; Guzzi, Marco; Huston, Joey; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C P
2015-01-01
We present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various $\\alpha_s$ values and additional sets in heavy-quark scheme with up to 3, 4, and 6 active flavors.
High energy deep inelastic scattering in perturbative quantum chromodynamics
In this PhD thesis, we deal with high energy Deep Inelastic Scattering in Perturbative Quantum Chromodynamics (QCD). In this work, two main topics are emphasized: The first one deals with dynamics based on perturbative renormalization group, and on perturbative Regge approaches. We discuss the applicability of these predictions, the possibility of distinguishing them in the HERA experiments, and their unification. We prove that the perturbative Regge dynamic can be successfully applied to describe the HERA data. Different observables are proposed for distinguishing these two approaches. We show that these two predictions can be unified in a system of equations. In the second one, unitarization and saturation problems in high energy QCD are discussed. In the multi-Regge approach, equivalent to the integrable one-dimensional XXX Heisenberg spin chain, we develop methods in order to solve this system, based on the Functional Bethe Ansatz. In the dipole model context, we propose a new formulation of unitarity and saturation effects, using Wilson loops. (author)
Lattice analysis of SU(2) chromodynamics with light quarks
I report on the Monte-Carlo simulation of a SU(2) lattice gauge theory which includes dynamical Kogut-Susskind quarks. On a 16*83 lattice the masses of ρ and π mesons are studied, the condensate measuring the chiral symmetry breaking determined, and the potential between static quarks measured. Extrapolations to vanishing quark mass yield a finite ρ mass but a value for the π mass which is compatible with zero, as well as a result different from zero for the quark condensate in accordance with the spontaneous breaking of the chiral symmetry of massless non-Abelian gauge theories. The shape of the q-anti q potential equals the pure gauge potential for small to intermediate distances. However at large distances (σ(fm)) deviations from the linear increase are indicated as they are expected due to the breakup of the flux tube between heavy quarks because of spontaneous quark-pair production. For all numerical calculations it is common that they favor a value for the scale parameter Λsub(anti Manti S)(NF=4) of quantum chromodynamics which is smaller than in the pure gauge field theory. (orig.)
Quantum Chromodynamics -- The Perfect Yang-Mills Gauge Field Theory
Gross, David
David Gross: My talk today is about the most beautiful of all Yang-Mills Theories (non-Abelian gauge theories), the theory of the strong nuclear interactions, Quantum Chromodynamics, QCD. We are celebrating 60 years of the publication of a remarkable paper which introduced the concept of non-Abelian local gauge symmetries, now called the Yang-Mills theory, to physics. In the introduction to this paper it is noted that the usual principle of isotopic spin symmetry is not consistent with the concept of localized fields. This sentence has drawn attention over the years because the usual principle of isotopic spin symmetry is consistent, it is just not satisfactory. The authors, Yang and Mills, introduced a more satisfactory notion of local symmetry which did not require one to rotate (in isotopic spin space) the whole universe at once to achieve the symmetry transformation. Global symmetries are thus are similar to `action at a distance', whereas Yang-Mills theory is manifestly local...
Factorization of exclusive processes in perturbative quantum-chromodynamics
The work carried out in this thesis presents various theoretical and phenomenological studies of the exclusive production of longitudinally polarized neutral vector rho mesons in virtual photons collisions, within the framework of quantum-chromodynamics (QCD). The virtuality of the photons makes it possible to locate our approach in the perturbative area of the theory. The kinematical regimes considered allow the use of varied theoretical tools which reveal various properties of factorization of the scattering amplitude: two types of collinear factorization (at short distance) for this process are discussed in chapter 1, revealing - according to the polarization of the virtual photons and the kinematical limit considered- Generalized Distribution Amplitudes (GDA) or Transition Distribution Amplitudes (TDA), tools commonly used in the description of exclusive processes. We introduce into the Chapter 2 in a self-consistent way, the foundations of the BFKL (Balitskii, Fadin, Kuraev and Lipatov) formalism valid within the high energy limit (Regge limit) of QCD, for its phenomenological use detailed in Chapter 3: the scattering amplitude of the process is described in this formalism by exploiting the factorization in the two-dimensional transverse momentum space, or kT-factorization. We predict the value of the cross section of the process at Born order of the BFKL resummation and we discuss its possible observation at the future international linear collider (ILC). We consider also the differential cross sections of the process without momentum transfer with complete BFKL evolution at the order of the leading logarithms (Leading-Order) and also at the Next-to-Leading-Order to establish a fine test of this process with hard BFKL Pomeron exchange, observable at the future ILC. (author)
Multi-Hadron Observables from Lattice Quantum Chromodynamics
Hansen, Maxwell [Univ. of Washington, Seattle, WA (United States)
2014-01-01
We describe formal work that relates the nite-volume spectrum in a quantum eld theory to scattering and decay amplitudes. This is of particular relevance to numerical calculations performed using Lattice Quantum Chromodynamics (LQCD). Correlators calculated using LQCD can only be determined on the Euclidean time axis. For this reason the standard method of determining scattering amplitudes via the Lehmann-Symanzik-Zimmermann reduction formula cannot be employed. By contrast, the nite-volume spectrum is directly accessible in LQCD calculations. Formalism for relating the spectrum to physical scattering observables is thus highly desirable. In this thesis we develop tools for extracting physical information from LQCD for four types of observables. First we analyze systems with multiple, strongly-coupled two-scalar channels. Here we accommodate both identical and nonidentical scalars, and in the latter case allow for degenerate as well as nondegenerate particle masses. Using relativistic eld theory, and summing to all orders in perturbation theory, we derive a result relating the nite-volume spectrum to the two-to-two scattering amplitudes of the coupled-channel theory. This generalizes the formalism of Martin L uscher for the case of single-channel scattering. Second we consider the weak decay of a single particle into multiple, coupled two-scalar channels. We show how the nite-volume matrix element extracted in LQCD is related to matrix elements of asymptotic two-particle states, and thus to decay amplitudes. This generalizes work by Laurent Lellouch and Martin L uscher. Third we extend the method for extracting matrix elements by considering currents which insert energy, momentum and angular momentum. This allows one to extract transition matrix elements and form factors from LQCD. Finally we look beyond two-particle systems to those with three-particles in asymptotic states. Working again to all orders in relativistic eld theory, we derive a relation between the
Lattice quantum chromodynamics and properties of the nucleon
The goal of this thesis is to compute from first principles nucleon properties, starting from the microscopic theory of strong interaction, quantum chromodynamics (QCD). This theory, whose degrees of freedom are quarks and gluons, has been well tested in high energy experiments thanks to asymptotic freedom, the fact that interaction cancels at short distances, which allows the use of the perturbative theory. To predict properties which involve long distances, like masses or current distributions, one needs an exact treatment of the theory. It uses a four-dimensional lattice on which the theory is discretized and quantum observables are computed through path integral techniques, as explained in chapters 2 and 3. In chapter 4 we discuss problems faced when fermions are taken into account and we present the choice for our computations: a discretization in a 'Wilson' manner plus an additional twisted mass. Its advantage is to remove discretization effects of the order of the lattice spacing provided one parameter is tuned. The numerical evaluation of path integrals is done by Monte Carlo methods with importance sampling. The 'Hybrid Monte Carlo' algorithm, based on molecular dynamics, is presented in chapter 5 together with a method to solve large sparse linear systems necessary to compute observables. This chapter also describes computer science details of the problem which are the use of massive parallel processing and some characteristics of computers used. In chapter 6 we explain how the production of representative samples of gauge configuration is performed. This step and its control is an important part of the work done during this thesis. The last two chapters are devoted to the computation of observables and to the presentation of results. The main technical difficulty which is to solve for quark propagators has been performed by using available processor farms at their best. A good part of this work has been focused on this. To conclude we comment on the
Chiral symmetry breakdown and the spectrum of pseudoscalar mesons in quantum chromodynamics
The recently suggested mechanism of the dynamical chiral symmetry breakdown in quantum chromodynamics is extended to the realistic situation when both spontaneous and explicit chiral symmetry breaking take place (current masses of the light quarks are different from zero). The mass relations for pseudoscalar nonet are obtained
Parton transverse momenta and quantum-chromodynamic effects in large-p/sub T/ hadron production
Inclusive pion production at large transverse momenta in pp collisions is studied in the framework of parton-parton scattering with partons carrying transverse momentum and with quark and gluon distributions determined from exact requirements of quantum chromodynamics. CERN ISR data are fairly well accounted for, but Fermilab data somewhat exceed the predictions. Gluon effects are considered in detail
Relating inclusive e+e- annihilation to electroproduction sum rules in Quantum Chromodynamics
Crewther, R. J.
1997-01-01
The Broadhurst-Kataev conjecture, that the ``discrepancy'' in the connection with the $\\pi^0 \\to \\gamma\\gamma$ anomaly equals the beta function $\\beta(\\bar{\\alpha})$ times a power series in the effective coupling $\\bar{\\alpha}$, is proven to all orders of perturbative quantum chromodynamics. The use of nested short-distance expansions is justified via Weinberg's power-counting theorem.
Thomas, Dean P; Hands, Simon
2016-01-01
The use of topology for visualisation applications has become increasingly popular due to its ability to summarise data at a high level. Criticalities in scalar field data are used by visualisation methods such as the Reeb graph and contour trees to present topological structure in simple graph based formats. These techniques can be used to segment the input field, recognising the boundaries between multiple objects, allowing whole contour meshes to be seeded as separate objects. In this paper we demonstrate the use of topology based techniques when applied to theoretical physics data generated from Quantum Chromodynamics simulations, which due to its structure complicates their use. We also discuss how the output of algorithms involved in topological visualisation can be used by physicists to further their understanding of Quantum Chromodynamics.
The properties of the transverse momenta and angular distributions of hadrons produced in muon-proton scattering with first-order quantum-chromodynamics calculations. The quantum-chromodynamics prediction for the Q2 dependence of the average hadron transverse momentum squared agrees with the data provided a constant term is added in quadrature to the prediction. This additive term is attributed to the intrinsic transverse momentum of the quarks in the nucleon and to the transverse momentum inherent in quark fragmentation
Parton densities in quantum chromodynamics gauge invariance, path-dependence and Wilson lines
Cherednikov, Igor O
2016-01-01
The purpose of this book is to give a systematic pedagogical exposition of the quantitative analysis of Wilson lines and loops in quantum chromodynamics. Using techniques from the previous volume (Wilson Lines in Quantum Field Theory, 2014), ab initio techniques are developed and practical tools for their implementation presented. An emphasis is put on their renormalization and on implications on processes observable at experimental facilities.
High corrections to the sigmasub(tot)(e+e-→hadrons) in quantum chromodynamics
In the framework of quantum chromodynamics the problem of correct calculation of the σsub(tot)(esup(+)esup(-) → hadron) process. It is indicated that at modern energies the effective strong coupling constant anti asub(s) is not too small. In connection with this high corrections are obtained to the cross section of the process. The corrections enable the agreement of the theory with the experimental data
Verifying Unmatter by Experiments, More Types of Unmatter, and a Quantum Chromodynamics Formula
Smarandache F.
2005-07-01
Full Text Available As shown, experiments registered unmatter: a new kind of matter whose atoms include both nucleons and anti-nucleons, while their life span was very short, no more than 10^−20 sec. Stable states of unmatter can be built on quarks and anti-quarks: applying the unmatter principle here it is obtained a quantum chromodynamics formula that gives many combinations of unmatter built on quarks and anti-quarks.
The colour of gluon interactions : Studies of Quantum Chromodynamics in soft and hard processes
Tîmneanu, Nicuşor
2002-01-01
Quantum Chromodynamics (QCD) is the theory of the strong interaction, one of the fundamental forces of nature. The interactions between quarks are mediated by gluons, which are the colour-charged gauge fields in QCD. Hard processes with a large momentum transfer can be calculated using perturbation theory, while soft processes with a small momentum transfer are poorly understood. In this thesis, various aspects of the gluon interactions are studied based on the interplay between hard and soft...
Deconfinement at finite temperature and the continuum limit of lattice quantum chromodynamics
The results of a Monte Carlo simulation of lattice Quantum Chromodynamics at finite temperature are presented. A qualitative theoretical picture of the deconfining phase transition is developed and used to guide this analysis of the Monte Carlo data. For lattice couplings g2 > 1, the critical temperature shows a clear deviation from asymptotic scaling as given by the perturbative β function. Below g2 = 1, a behaviour consistent with asymptotic scaling is observed. Finite size scaling in used to analyse the dependence of the critical temperature on the spatial volume of the lattice. A brief description of the author's CDC CYBER 205 computer program is also given
Corrections to quantum-chromodynamic Born terms. II. Transverse-momentum distribution of dileptons
Quantum-chromodynamic corrections to the transverse-momentum distribution of dileptons are determined. For p+p → l+l-+X the dominant Born term is known to be provided by the subprocess q+g → q+γ*; the corrections are due to q+q → q+q+γ*. At large transverse momenta these corrections are found to be significant, and improve agreement with experiment. As a by-product, factorization of mass singularities and the implementation of scale violations in the gluon distribution are explicitly shown
Phase transition and density of states in the quantum-chromodynamic bag model
In the context of a two-phase model of hadronic matter suggested by Hagedorn and Rafelski, an analysis of a quark-gluon plasma described by perturbative quantum chromodynamics supplemented by a bag constant to account for nonperturbative effects is presented. A running coupling constant is explicitly implemented. The critical temperature and energy density are determined and the conditions under which T/sub c/< B/sup 1/4/ are discussed. Next, the asymptotic density of hadronic states is derived by Laplace-inverting the partition function and the same form as in the statistical bootstrap model is obtained
Light-Front Quantum Chromodynamics: A framework for the analysis of hadron physics
Bakker, B L G; Brodsky, S J; Broniowski, W; Dalley, S; Frederico, T; Glazek, S D; Hiller, J R; Ji, C -R; Karmanov, V; Kulshreshtha, D; Mathiot, J -F; Melnitchouk, W; Miller, G A; Papavassiliou, J; Polyzou, W N; Stefanis, N G; Vary, J P; Ilderton, A; Heinzl, T
2013-01-01
An outstanding goal of physics is to find solutions that describe hadrons in the theory of strong interactions, Quantum Chromodynamics (QCD). For this goal, the light-front Hamiltonian formulation of QCD (LFQCD) is a complementary approach to the well-established lattice gauge method. LFQCD offers access to the hadrons' nonperturbative quark and gluon amplitudes, which are directly testable in experiments at existing and future facilities. We present an overview of the promises and challenges of LFQCD in the context of unsolved issues in QCD that require broadened and accelerated investigation. We identify specific goals of this approach and address its quantifiable uncertainties.
A number of novel features of QCD are reviewed, including the consequences of formation zone and color transparency phenomena in hadronic collisions, the use of automatic scale setting for perturbative predictions, null-zone phenomena as a fundamental test of gauge theory, and the relationship of intrinsic heavy colored particle Fock state components to new particle production. We conclude with a review of the applications of QCD to nuclear multiquark systems. 74 references
Fried, H. M.; Müller, B.; Gabellini, Y.
2000-11-01
The Table of Contents for the full book PDF is as follows: * Preface * Basic Concepts and Consequences of a Stochastic Vacuum Model * The Role of the QCD Vacuum in the Heavy-Quark Bound State Dynamics * Stochastic Vacuum Model and High Energy Scattering * Variational Approximations for Correlation Functions in Quantum Field Theories * Long-Range Vacuum Correlations? * Unitary Gauge Theories in Singlet Coordinates * SU(2) Gauge Theory in Covariant (Maximal) Abelian Gauges * Dynamics and Topology of the Gauge-Invariant Gauge Field in Two-Color QCD * The Vacuum Wave Function in Supersymmetric Matrix Theory * Analytic Models for the Forward Scattering Amplitude at High Energies * Extending the Frontiers -- Reconciling Accelerator and Cosmic Ray p - p Cross Sections * HERA Results on Elastic Hadronic and Sub-Hadronic Diffraction * Small-x Structure Functions and QCD Pomeron * AdS/CFT Correspondence for QCD and Pomeron Intercept at Strong Coupling * Short Introduction to QGP Dynamics * Effective Theories for Hot Non-Abelian Dynamics * Non-Perturbative Gluodynamics of High Enerry Heavy-Ion Collisions * Deriving Effective Transport Equations for Non-Abelian Plasmas * Ergodic Properties of Non-Abelian Gauge Theories * String from Large Nc Gauge Fields via Graph Summation on a P+ - x+ Lattice * Aspects of Non-Commutativity in ADS/CFT * Eikonal Scattering of Monopoles and Dyons in Dual QED * Gluon Reggeization and Sudakov Suppression via The Fock-Feynman-Schwinger Approach to QCD * Nonperturbative Gluon Radiation and Energy Dependence of Elastic Scattering * Thermal Field Theory in Equilibrium * Puzzling Aspects of Hot Quantum Fields * Color Superconductivity in Cold, Dense Quark Matter * DIS Results from HERA * Electroproduction of Vector Mesons * Probing the QED and QCD Vacua * New Developments in Cosmology * Duality and SU(1,1) coherent states in the Calogero-Moser Model * pp Elastic scattering at LHC and Signature of Chiral Phase Transition at Large |t| * A New Basis Function Approach to 't Hooft Equation * The Heavy Hadron Spectrum and mb from Lattice QCD * Heavy-Light Physics from Lattice NRQCD * Quarkonium Decays and Production in NRQCD * Polarization of Prompt J/ψ at the Tevatron * Non-Relativistic Effective Field Theory for Perturbative Heavy Quark-Antiquark Systems * Accelerating, Storing and Scattering Polarized Protons * Phenomenology of Tlansverse Single Spin Asymmetries in Inclusive Processes * The Spin Dependence of Swift Proton Collisions * Numerical Investigation of Domain-Wall QCD on CP-PACS * New Results for the Spin-Dependent Total Cross Section Difference ΔσL (np) Over the GeV Energy Region * When is it Possible to Use Perturbation Technique in Field Theory? * List of Participants
The symposium included lectures covering both the elements and the experimental tests of the theory of quantum chromdynamics. A three day topical conference was included which included the first results from PETRA as well as the latest reports from CERN, Fermilab, and SPEAR experiments. Twenty-one items from the symposium were prepared separately for the data base
Nowadays, the study of scattering and production of particles occupies an important place in subatomic physics research. The main ongoing experiments concern high-energy scattering in the colliders, the scattering theory based on quantum field theory is used for the theoretical study. The work presented in this thesis is located in this framework, in fact it concerns a study on the scattering theory and Perturbative Quantum Chromodynamics. We used the path integral formalism of quantum field theory and perturbation theory. As we considered the higher order corrections in perturbative developments, the renormalization theory with the method of dimensional regularization was also used. As an application, the case of the Top quark production was considered. As main results, we can quote the obtention of the cross section of quark-antiquark top pair production up to second order.
Studying the thermodynamics of gases, lattices and other statistical systems via numerical simulations requires the mapping of energy density, pressure and other quantities as functions of temperature. Of special importance is the accurate mapping near and at phase transitions, where discontinuities are present and difficult to measure with a limited number of computerized simulations. This is particularly true for Quantum Chromodynamics, the theory of quarks and gluons, which is known to have a first-order phase transition at a temperature of about 150 MeV. This paper shows that by using the recently proposed method of density of states, one can optimize the information obtained from these limited simulations with supercomputers in order to obtain in the worst cases the derivative of the thermodynamical functions, and in the best cases, their entire curve over a wide range of temperatures
Parallelizing the QUDA Library for Multi-GPU Calculations in Lattice Quantum Chromodynamics
Babich, Ronald; Joó, Bálint
2010-01-01
Graphics Processing Units (GPUs) are having a transformational effect on numerical lattice quantum chromodynamics (LQCD) calculations of importance in nuclear and particle physics. The QUDA library provides a package of mixed precision sparse matrix linear solvers for LQCD applications, supporting single GPUs based on NVIDIA's Compute Unified Device Architecture (CUDA). This library, interfaced to the QDP++/Chroma framework for LQCD calculations, is currently in production use on the "9g" cluster at the Jefferson Laboratory, enabling unprecedented price/performance for a range of problems in LQCD. Nevertheless, memory constraints on current GPU devices limit the problem sizes that can be tackled. In this contribution we describe the parallelization of the QUDA library onto multiple GPUs using MPI, including strategies for the overlapping of communication and computation. We report on both weak and strong scaling for up to 32 GPUs interconnected by InfiniBand, on which we sustain in excess of 4 Tflops.
Azaria, P; Lecheminant, Ph; Palmai, T; Takacs, G; Tsvelik, A M
2016-01-01
In this paper we study a (1+1)-dimensional version of the famous Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and finite matter density. We use non-perturbative techniques (non-Abelian bosonization and Truncated Conformal Space Approach). At zero density we describe a formation of fermion three-quark (nucleons and $\\Delta$-baryons) and boson (two-quark mesons, six-quark deuterons) bound states and also a formation of a topologically nontrivial phase. At finite matter density, the model has a rich phase diagram which includes phases with density wave and superfluid quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results as a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).
Introduction to non-perturbative quantum chromodynamics; Introduction a QCD non perturbatif
Pene, O. [Paris-11 Univ., 91 - Orsay (France). Lab. de Physique Theorique et Hautes Energies
1995-12-31
Quantum chromodynamics is considered to be the theory of strong interaction. The main peculiarity of this theory is that its asymptotic states (hadrons) are different from its elementary fields (quarks and gluons). This property plays a great part in any physical process involving small momentum-energy transfers. In such a range perturbative methods are no longer allowed. This work focuses on other tools such as QCD symmetry, the quark model, Green functions and the sum rules. To get hadron characteristics numerically, QCD on lattices is used but only in the case of simple process involving no more than one hadron in the initial and final states because of the complexity of the Green function. Some examples using a Monte-Carlo simulation are given. (A.C.) 39 refs.
An operatorially solved model of massless two-dimensional quantum chromodynamics
An operator solution is constructed in (1, 1) dimensions to the massless quantum chromodynamics of n fermion quarks and n2 - 1 vector boson gluons with local colour SU(n) symmetry. The interacting quark field is a confined SU(n) Thirring field with zero Abelian coupling. The colour gluons are dependent Lie fields obeying the gluon-free fermionic current identity. Explicit local infinitesimal operator colour transformations (with an arbitrary coordinate-independent Lorentz vector coefficient defining the gauge) are given and the requirement of proper colour covariance linked to the vanishing of the coloured quark source currents and hence to the absence of coloured quark-composite states. The status of Noether's theorem is also clarified. (Auth.)
Resonant π^{+}γ→π^{+}π^{0} Amplitude from Quantum Chromodynamics.
Briceño, Raúl A; Dudek, Jozef J; Edwards, Robert G; Shultz, Christian J; Thomas, Christopher E; Wilson, David J
2015-12-11
We present the first ab initio calculation of a radiative transition of a hadronic resonance within quantum chromodynamics (QCD). We compute the amplitude for ππ→πγ^{⋆}, as a function of the energy of the ππ pair and the virtuality of the photon, in the kinematic regime where ππ couples strongly to the unstable ρ resonance. This exploratory calculation is performed using a lattice discretization of QCD with quark masses corresponding to m_{π}≈400 MeV. We obtain a description of the energy dependence of the transition amplitude, constrained at 48 kinematic points, that we can analytically continue to the ρ pole and identify from its residue the ρ→πγ^{⋆} form factor. PMID:26705626
Azaria, P.; Konik, R. M.; Lecheminant, P.; Pálmai, T.; Takács, G.; Tsvelik, A. M.
2016-08-01
In this paper we study a (1 +1 )-dimensional version of the famous Nambu-Jona-Lasinio model of quantum chromodynamics (QCD2) both at zero and at finite baryon density. We use nonperturbative techniques (non-Abelian bosonization and the truncated conformal spectrum approach). When the baryon chemical potential, μ , is zero, we describe the formation of fermion three-quark (nucleons and Δ baryons) and boson (two-quark mesons, six-quark deuterons) bound states. We also study at μ =0 the formation of a topologically nontrivial phase. When the chemical potential exceeds the critical value and a finite baryon density appears, the model has a rich phase diagram which includes phases with a density wave and superfluid quasi-long-range (QLR) order, as well as a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results in either a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).
Connecting the hadron mass scale to the fundamental mass scale of quantum chromodynamics
A. Deur
2015-11-01
Full Text Available Establishing an explicit connection between the long distance physics of confinement and the dynamical interactions of quarks and gluons at short distances has been a long-sought goal of quantum chromodynamics. Using holographic QCD, we derive a direct analytic relation between the scale κ which determines the masses of hadrons and the scale Λs which controls the predictions of perturbative QCD at very short distances. The resulting prediction Λs=0.341±0.032 GeV in the MS‾ scheme agrees well with the experimental average 0.339±0.016 GeV. We also derive a relation between Λs and the QCD string tension σ. This connection between the fundamental hadronic scale underlying the physics of quark confinement and the perturbative QCD scale controlling hard collisions can be carried out in any renormalization scheme.
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density. Finally, we discuss the interplay between relativistic quantum field theories (including quantum
It is argued that the 't Hooft transformation of the running coupling constant, in which the two-loop renormalization group (RG) function becomes exact, will be useful in the framework of perturbative quantum chromodynamics at least to three-loop order. On the other hand, the coupling constant expansion obtained by the Adler transformation, in which the RG equation takes its one-loop form, may suffer from large corrections in a finite order. (orig.)
Demonstration of string breaking in quantum chromodynamics by large-scale eigenvalue computations
Attig, N.; Bali, G. S.; Düssel, Th.; Lippert, Th.; Neff, H.; Prkaçin, Z.; Schilling, K.
2005-07-01
We present results of our ongoing determination of "string breaking" in quantum chromodynamics (QCD) including two dynamical light quarks. Our investigation of the fission of the string between a heavy (static) quark and a corresponding antiquark into a meson-antimeson system is based on dynamical configurations of size 24×40. The all-to-all light quark propagators occurring in the transition element are computed from a set of 200 low-lying eigenmodes of the Hermitian Wilson-Dirac matrix which encodes the effect of the dynamical quarks. These eigenmodes are calculated on the 1312-node IBM p690 system at the John von Neumann Institute in Jülich. Combining the eigenvalue computations with a variety of ground state enhancing optimization methods we determine the matrix elements of the two-by-two system with so far unprecedented accuracy. We observe—for the first time ever in a simulation of 4-dimensional lattice-QCD— level-splitting as the perfect signature for dynamical string breaking between ground state and excited potential.
Gauge invariant description of heavy quark bound states in quantum chromodynamics
A model for a heavy quark meson is proposed in the framework of a gauge-invariant version of quantum chromodynamics. The field operators in this formulation are taken to be Wilson loops and strings with quark-antiquark ends. The fundamental differential equations of point-like Q.C.D. are expressed as variational equations of the extended loops and strings. The 1/N expansion is described, and it is assumed that nonleading effects such as intermediate quark pairs and nonplanar gluonic terms can be neglected. The action of the Hamiltonian in the A0 = 0 gauge on a string operator is derived. A trial meson wave functional is constructed consisting of a path-averaged string operator applied to the full vacuum. A Gaussian in the derivative of the path location is assumed for the minimal form of the measure over paths. A variational parameter is incorporated in the measure as the exponentiated coefficient of the squared path location. The expectation value of the Hamiltonian in the trial state is evaluated for the assumption that the negative logarithm of the expectation value of a Wilson loop is proportional to the loop area. The energy is then minimized by deriving the equivalent quantum mechanical Schroedinger's equation and using the quantum mechanical 1/n expansion to estimate the effective eigenvalues. It is found that the area law behavior of the Wilson loop implies a nonzero best value of the variational parameter corresponding to a quantum broadening of the flux tube
Phenomenological SU(6) breaking of baryon wave functions and the chromodynamic spin-spin force
A contradiction is found between two successful models of SU(6) breaking. A quark-model mixing scheme (56,0+) + (70,0+) for the baryon octet has been devised to explain the ratio F/sup e/n2(x)/F/sup e/p2(x) in the valence-quark region and explains naturally other departures from the usual SU(6) predictions. On the other hand, the gluon-exchange model of SU(6) breaking accounts satisfactorily for the hadron spectrum splittings. The spin-spin contribution from this chromodynamic force is indeed shown to generate a (56,0+) + (70,0+) mixing of the octet. However, it yields a wrong sign for the mixing angle, thus pointing to a contradiction between spin-spin forces of one-gluon-exchange type and the deep-inelastic structure functions in the valence-quark region. Other spin-spin potentials, giving the right sign for the mixing angle, are shown to be also in difficulty, because of the hyperfine structure of excited levels. Finally, a careful discussion is made of the subtle Σ-Λ effect in both approaches
Study of the meson mass spectroscopy with a potential model inspired in the quantum chromodynamics
Since the discovery of QCD (Quantum Chromodynamics), there have been remarkable technical achievements in perturbative calculations applied to hadrons. However, it is difficult to use QCD directly to compute hadronic properties. In this context, phenomenological potential models have provided extremely satisfactory results on description of ordinary hadrons, more specifically about quark-antiquark bound states (mesons). In this work we propose and study the main aspects in the construction of a potential model and search a generalized description of meson spectroscopy, with emphasis in heavy quark bound states. We analyze important aspects in the choice of the treatment in good agreement with the dynamics of interacting particles, attempting to relativistic aspects as well as to the possibilities of nonrelativistic approximation analysis. Initially the 'soft QCD' is employed to determine effective potential terms establishing the asymptotic Coulomb term from one gluon exchange approximation. At the same time, a linear confinement term is introduced in accordance with QCD and phenomenological prescription. We perform the calculations of mass spectroscopy for particular sets of mesons and we verify whether the potential model could be extended to calculating the electronic transition rate (Γ(q q-bar → e-e+)). Finishing, we discuss the real physical possibilities of development of a generalized potential model (all quark flavors), its possible advantages relative to experimental parametrization, complexity in numerical calculations and in the description of physical reality in agreement with a quantum field theory (QCD). (author)
Net-proton measurements at RHIC and the quantum chromodynamics phase diagram
Bedangadas Mohanty
2014-11-01
Two measurements related to the proton and antiproton production near midrapidity in $\\sqrt{s_{NN}}$ = 7.7, 11.5, 19.6, 27, 39, 62.4 and 200 GeV Au+Au collisions using the STAR detector at the Relativistic Heavy Ion Collider (RHIC) are discussed. At intermediate impact parameters, the net-proton midrapidity d$v_1$/d, where $v_1$ and are directed flow and rapidity, respectively, shows non-monotonic variation as a function of beam energy. This non-monotonic variation is characterized by the presence of a minimum in d$v_1$/d between $\\sqrt{s_{NN}}$ = 11.5 and 19.6 GeV and a change in the sign of d$v_1$/d twice between $\\sqrt{s_{NN}}$ = 7.7 and 39 GeV. At small impact parameters the product of the moments of net-proton distribution, kurtosis × variance ( 2) and skewness × standard deviation ($S$) are observed to be significantly below the corresponding measurements at large impact parameter collisions for $\\sqrt{s_{NN}}$ = 19.6 and 27 GeV. The 2 and $S$ values at these beam energies deviate from the expectations from Poisson statistics and that from a hadron resonance gas model. Both these measurements have implications towards understanding the quantum chromodynamics (QCD) phase structures, the first-order phase transition and the critical point in the high baryonic chemical potential region of the phase diagram.
Topics in nuclear chromodynamics: Color transparency and hadronization in the nucleus
The nucleus plays two complimentary roles in quantum chromodynamics: (1) A nuclear target can be used as a control medium or background field to modify or probe quark and gluon subprocesses. Some novel examples are color transparency, the predicted transparency of the nucleus to hadrons participating in high momentum transfer exclusive reactions, and formation zone phenomena, the absence of hard, collinear, target-induced radiation by a quark or gluon interacting in a high momentum transfer inclusive reaction if its energy is large compared to a scale proportional to the length of the target. (Soft radiation and elastic initial state interactions in the nucleus still occur.) Coalescence with co-moving spectators is discussed as a mechanism which can lead to increased open charm hadroproduction, but which also suppresses forward charmonium production (relative to lepton pairs) in heavy ion collisions. Also discussed are some novel features of nuclear diffractive amplitudes--high energy hadronic or electromagnetic reactions which leave the entire nucleus intact and give nonadditive contributions to the nuclear structure function at low /kappa cur//sub Bj/. (2) Conversely, the nucleus can be studied as a QCD structure. At short distances, nuclear wave functions and nuclear interactions necessarily involve hidden color, degrees of freedom orthogonal to the channels described by the usual nucleon or isobar degrees of freedom. At asymptotic momentum transfer, the deuteron form factor and distribution amplitude are rigorously calculable. One can also derive new types of testable scaling laws for exclusive nuclear amplitudes in terms of the reduced amplitude formalism
Quantum chromodynamics at high energy, theory and phenomenology at hadron colliders
When probing small distances inside a hadron, one can resolve its partonic constituents: quarks and gluons that obey the laws of perturbative Quantum Chromodynamics (QCD). This substructure reveals itself in hadronic collisions characterized by a large momentum transfer: in such collisions, a hadron acts like a collection of partons whose interactions can be described in QCD. In a collision at moderate energy, a hadron looks dilute and the partons interact incoherently. As the collision energy increases, the parton density inside the hadron grows. Eventually, at some energy much bigger than the momentum transfer, one enters the saturation regime of QCD: the gluon density has become so large that collective effects are important. We introduce a formalism suitable to study hadronic collisions in the high-energy limit in QCD, and the transition to the saturation regime. In this framework, we derive known results that are needed to present our personal contributions and we compute different cross-sections in the context of hard diffraction and particle production. We study the transition to the saturation regime as given by the Balitsky-Kovchegov equation. In particular we derive properties of its solutions.We apply our results to deep inelastic scattering and show that, in the energy range of the HERA collider, the predictions of high-energy QCD are in good agreement with the data. We also consider jet production in hadronic collisions and discuss the possibility to test saturation at the Large Hadron Collider. (author)
Finite-Volume Effects in Quantum Chromodynamics and Functional Renormalization Group Methods
Quantum Chromodynamics (QCD) at finite temperature and density is currently a subject of great interest, due to both advances in experimental heavy-ion collisions and theoretical improvement of our understanding in recent years. Simulations of the theory on finite space-time lattices provide important theoretical advances. But in particular for investigating QCD phase transitions, finite quark masses and finite volumes in the simulations need to be taken into account. The investigation of finite-volume effects in QCD has a long tradition in the framework of chiral perturbation theory and random matrix theory and can provide useful tools for the analysis. With regard to a description of the chiral phase transition in QCD, it is very important to correctly take into account the effects of long-range fluctuations such as pions as the Goldstone bosons of spontaneous chiral symmetry breaking. It is natural to employ Renormalization Group methods for this purpose. Together with Hans-Juergen Pirner, we have initiated work in this direction, and there has been an increasing interest in the investigation of such finite-volume effects. I will give an overview over recent developments. (author)
Phenomenology of the proton and the nucleus through hard processes in quantum chromodynamics
My scientific domain is the phenomenology of the non-perturbative quantum chromodynamics (QCD). In the introduction I quickly present the history of QCD since its establishing in the seventies. The first chapter is dedicated to the achievements of the last decade concerning first the hard electroproduction at low impulse transfer in electron-proton reactions and secondly the search for the quark-gluon plasma in ultra-relativistic heavy ion reactions with the help of hard probes. In the second chapter I detail the hard electroproduction reactions with the aim of explaining their factorization in a sub-process including partons and whose amplitude can be computed in the theory of perturbations. Generalized parton distributions, that describe the transition from hadrons to partons could be useful to get more information on hadronic wave functions. Experimental implications are reviewed. The third chapter is dedicated to the J/ψ production in proton-nucleus collisions. J/ψ and the quarkonium family offer, thanks to their easy identification a useful tool to shed light on different sides of QCD such as the production of heavy quarks or the existence of the quark-gluon plasma. In the last chapter I present my last works that concern first the nuclear effects that appear in proton-nucleus collisions when we want to describe the relationship between the production cross-section of a particle and the value of the transverse momentum of the particle, and secondly the observation through radio-detection of big showers due to the interaction with the atmosphere of an ultra-high energy cosmic ray
Simulation of quantum chromodynamics on the lattice with exactly chiral lattice fermions
Aoki, Sinya; Chiu, Ting-Wai; Cossu, Guido; Feng, Xu; Fukaya, Hidenori; Hashimoto, Shoji; Hsieh, Tung-Han; Kaneko, Takashi; Matsufuru, Hideo; Noaki, Jun-Ichi; Onogi, Tetsuya; Shintani, Eigo; Takeda, Kouhei
2012-09-01
Numerical simulation of the low-energy dynamics of quarks and gluons is now feasible based on the fundamental theory of strong interaction, i.e. quantum chromodynamics (QCD). With QCD formulated on a 4D hypercubic lattice (called lattice QCD or LQCD), one can simulate the QCD vacuum and hadronic excitations on the vacuum using teraflop-scale supercomputers, which have become available in the last decade. A great deal of work has been done on this subject by many groups around the world; in this article we summarize the work done by the JLQCD and TWQCD collaborations since 2006. These collaborations employ Neuberger's overlap fermion formulation, which preserves the exact chiral and flavor symmetries on the lattice, unlike other lattice fermion formulations. Because of this beautiful property, numerical simulation of the formulation can address fundamental questions on the QCD vacuum, such as the microscopic structure of the quark-antiquark condensate in the chirally broken phase of QCD and its relation to SU(3) gauge field topology. Tests of the chiral effective theory, which is based on the assumption that the chiral symmetry is spontaneously broken in the QCD vacuum, can be performed, including the pion-loop effect test. For many other phenomenological applications, we adopt the all-to-all quark propagator technique, which allows us to compute various correlation functions without substantial extra cost. The benefit of this is not only that the statistical signal is improved but that disconnected quark-loop diagrams can be calculated. Using this method combined with the overlap fermion formulation, we study a wide range of physical quantities that are of both theoretical and phenomenological interest.
Measurement of the lepton τ spectral functions and applications to quantum chromodynamic
This thesis presents measurements of the τ vector (V) and axial-vector (A) hadronic spectral functions and phenomenological studies in the framework of quantum chromodynamics (QCD). Using the hypothesis of conserved vector currents (CVC), the dominant two- and four-pion vector spectral functions are compared to the corresponding cross sections from e+e- annihilation. A combined fit of the pion form factor from τ decays and e+e- data is performed using different parametrizations. The mass and the width of the ρ±(770) and the ρ0(770) are separately determined in order to extract possible isospin violating effects. The mass and width differences are measured to be Mρ±(770) - Mρ0(770)=(0.0±1.0) MeV/c2 and Γρ±(770) - Γρ0(770)=(0.1 ± 1.9) MeV/c2. Several QCD chiral sum rules involving the difference (V - A) of the spectral functions are compared to their measurements. The Borel-transformed Das-Mathur-Okubo sum rule is used to measure the pion polarizability to be αE=(2.68±0.91) x 10-4 fm3. The τ vector and axial-vector hadronic widths and certain spectral moments are exploited to measure αs and non-perturbative contributions at the τ mass scale. The best, and experimentally and theoretically most robust, determination of αs(Mτ) is obtained from the inclusive (V + A) fit that yields αs(Mτ)= 0.348±0.017 giving αs(MZ)=0.1211 ± 0.0021 after the evolution to the mass of the Z boson. The approach of the Operator Product Expansion (OPE) is tested experimentally by means of an evolution of the τ hadronic width to masses smaller that the τ mass. Using the difference (V - A) of the spectral functions allows one to directly measure the dominant non-perturbative OPE dimension to be D=6.9±0.5. The vector spectral functions are used to improve the precision of the experimental determination of the hadronic contribution to the anomalous magnetic moment of the muon aμ=(g - 2)/2 and to the running of the QED fine structure constant αQED(MZ2) at the Z mass
We use variationally improved perturbation theory (VIPT) for calculating the elastic form factors and charge radii of D, Ds, B, Bs and Bc mesons in a quantum chromodynamics (QCD)-inspired potential model. For that, we use linear-cum-Coulombic potential and opt the Coulombic part first as parent and then the linear part as parent. The results show that charge radii and form factors are quite small for the Coulombic parent compared to the linear parent. Also, the analysis leads to a lower as well as upper bounds on the four-momentum transfer Q2, hinting at a workable range of Q2 within this approach, which may be useful in future experimental analyses. Comparison of both the options shows that the linear parent is the better option. (author)
Hülsing, Tobias
Quantum chromodynamics, QCD, the theory of the strong interaction is split into two regimes. Scattering processes of the proton constituents, the partons, with a high momentum transfer $Q^2$ can be calculated and predicted with perturbative calculations. At low momentum transfers between the scattering particles perturbation theory is not applicable anymore, and phenomenological methods are used to describe the physics in this regime. The ATLAS experiment at the Large Hadron Collider, LHC, provides the possibility to analyze QCD processes at both ends of the momentum scale. Two measurements are presented in this thesis, emphasizing one of the two regimes each: The measurement of charged-particle event shape variables in inelastic proton–proton collisions at a center-of-mass energy of $\\sqrt{s}$ = 7 TeV analyses the transverse momentum flow and structure of hadronic events. Due to the, on average, low momentum transfer, predictions of these events are mainly driven by non-perturbative models. Three event sha...
Bhaskar Jyoti Hazarika; D K choudhury
2015-01-01
We use variationally improved perturbation theory (VIPT) for calculating the elastic form factors and charge radii of , $D_{s}$, $B$, $B_{s}$ and $B_{c}$ mesons in a quantum chromodynamics (QCD)-inspired potential model. For that, we use linear-cum-Coulombic potential and opt the Coulombic part first as parent and then the linear part as parent. The results show that charge radii and form factors are quite small for the Coulombic parent compared to the linear parent. Also, the analysis leads to a lower as well as upper bounds on the four-momentum transfer 2, hinting at a workable range of 2 within this approach, which may be useful in future experimental analyses. Comparison of both the options shows that the linear parent is the better option.
Burch, T
2003-01-01
While we may know the overall quantum numbers of a given meson state and that such a state is necessarily a color singlet, we do not know a priori the relative spin and color alignments of the constituents: the quarks, antiquarks, and gluons. The overall meson wavefunction may have contributions from different spin- color configurations: one where the quark and antiquark alone account for the spin of the meson; or another where a gluon excitation also contributes to the total spin (a hybrid state), while helping to form the color singlet. The determination of the relative contributions of each these configurations to the overall meson state is the focus of this work. We use the lattice formulation of quantum chromodynamics (QCD) and we restrict our analysis to the limit of heavy quark masses. We are therefore able to use a non- relativistic approximation for the quark and antiquark Hamiltonians (NRQCD). This provides the additional separation of the spin- and orbital-angular-momentum degrees of freedom of the...
Wallon, S.
1996-09-17
In this PhD thesis, we deal with high energy Deep Inelastic Scattering in Perturbative Quantum Chromodynamics (QCD). In this work, two main topics are emphasized: The first one deals with dynamics based on perturbative renormalization group, and on perturbative Regge approaches. We discuss the applicability of these predictions, the possibility of distinguishing them in the HERA experiments, and their unification. We prove that the perturbative Regge dynamic can be successfully applied to describe the HERA data. Different observables are proposed for distinguishing these two approaches. We show that these two predictions can be unified in a system of equations. In the second one, unitarization and saturation problems in high energy QCD are discussed. In the multi-Regge approach, equivalent to the integrable one-dimensional XXX Heisenberg spin chain, we develop methods in order to solve this system, based on the Functional Bethe Ansatz. In the dipole model context, we propose a new formulation of unitarity and saturation effects, using Wilson loops. (author). 120 refs.
Perturbative quantum chromodynamics
Brodsky, S.J.
1979-12-01
The application of QCD to hadron dynamics at short distances, where asymptotic freedom allows a systematic perturbative approach, is addressed. The main theme of the approach is to incorporate systematically the effects of the hadronic wave function in large momentum transfer exclusive and inclusive reactions. Although it is conventional to treat the hadron as a classical source of on-shell quarks, there are important dynamical effects due to hadronic constituent structure which lead to a broader testing ground for QCD. QCD predictions are discussed for exclusive processes and form factors at large momentum transfer in which the short-distance behavior and the finite compositeness of the hadronic wave functions play crucial roles. Many of the standard tests of QCD are reviewed including the predictions for R = sigma/sub e/sup +/e/sup -/..-->..had//sigma/sub e/sup +/e/sup -/..--> mu../sup +/..mu../sup -//, the structure functions of hadrons and photons, jet phenomena, and the QCD corrections to deep inelastic processes. The exclusive-inclusive connection in QCD, the effects of power-law scale-breaking contributions, and the important role of the available energy in controlling logarithmic scale violations are also discussed. 150 references, 44 figures. (RWR)
Perturbative quantum chromodynamics
The application of QCD to hadron dynamics at short distances, where asymptotic freedom allows a systematic perturbative approach, is addressed. The main theme of the approach is to incorporate systematically the effects of the hadronic wave function in large momentum transfer exclusive and inclusive reactions. Although it is conventional to treat the hadron as a classical source of on-shell quarks, there are important dynamical effects due to hadronic constituent structure which lead to a broader testing ground for QCD. QCD predictions are discussed for exclusive processes and form factors at large momentum transfer in which the short-distance behavior and the finite compositeness of the hadronic wave functions play crucial roles. Many of the standard tests of QCD are reviewed including the predictions for R = sigma/sub e+e-→had//sigma/sub e+e-→μ+μ-/, the structure functions of hadrons and photons, jet phenomena, and the QCD corrections to deep inelastic processes. The exclusive-inclusive connection in QCD, the effects of power-law scale-breaking contributions, and the important role of the available energy in controlling logarithmic scale violations are also discussed. 150 references, 44 figures
Beyond standard quantum chromodynamics
Brodsky, S.J.
1995-09-01
Despite the many empirical successes of QCD, there are a number of intriguing experimental anomalies that have been observed in heavy flavor hadroproduction, in measurements of azimuthal correlations in deep inelastic processes, and in measurements of spin correlations in hadronic reactions. Such phenomena point to color coherence and multiparton correlations in the hadron wavefunctions and physics beyond standard leading twist factorization. Two new high precision tests of QCD and the Standard Model are discussed: classical polarized photoabsorption sum rules, which are sensitive to anomalous couplings and composite structure, and commensurate scale relations, which relate physical observables to each other without scale or scheme ambiguity. The relationship of anomalous couplings to composite structure is also discussed.
Quantum Chromodynamics (abstract only)
Hooft, G. 't
2000-01-01
The strong interactions were the last of the fundamental forces in the twentieth century to be fully understood in terms of basic and fundamental equations. Shortly after the discovery of the renormalizable non-Abelian gauge theories that unified the electroweak forces, it was realized that the stro
Signatures for axial chromodynamics
Within the context of basic left-right symmetry and the hypothesis of unification of weak, electromagnetic and strong forces at a mass level approximately equal to 104-106 GeV, relatively light ''mass'' axial gluons, confined or liberated, must be postulated. The authors remark that the existence of such ''light'' axial gluons supplementing the familiar vector octet preserves the successes of QCD, both for deep inelastic processes and charmonium physics. Through the characteristic spin-spin force, generated by their exchange, they may even help resolve some of the discrepancies between vector QCD predictions and charmonium physics. The main remark of this note is that if colour is liberated, not only vector but also axial-vector gluons are produced in high-energy e-e+ experiments, e.g. at PETRA and PEP, with fairly large cross-section. Distinctive decay modes of such liberated axial gluons are noted
Testing quantum chromodynamics
The difficulties in isolating specific QCD mechanisms which control hadronic phenomena, and the complications in obtaining quantitative tests of QCD are discussed. A number of novel QCD effects are reviewed, including heavy quark and higher twist phenomena, initial and final state interactions, direct processes, multiparticle collisions, color filtering, and nuclear target effects. The importance of understanding hadron production at the amplitude level is stressed
Testing quantum chromodynamics
Brodsky, S.J.
1982-09-01
The difficulties in isolating specific QCD mechanisms which control hadronic phenomena, and the complications in obtaining quantitative tests of QCD are discussed. A number of novel QCD effects are reviewed, including heavy quark and higher twist phenomena, initial and final state interactions, direct processes, multiparticle collisions, color filtering, and nuclear target effects. The importance of understanding hadron production at the amplitude level is stressed.
Quantum Chromodynamics: Computational Aspects
Schaefer, Thomas
2016-01-01
We present a brief introduction to QCD, the QCD phase diagram, and non-equilibrium phenomena in QCD. We emphasize aspects of the theory that can be addressed using computational methods, in particular euclidean path integral Monte Carlo, fluid dynamics, kinetic theory, classical field theory and holographic duality.
Quantum chromodynamics, QCD, the theory of the strong interaction is split into two regimes. Scattering processes of the proton constituents, the partons, with a high momentum transfer Q2 can be calculated and predicted with perturbative calculations. At low momentum transfers between the scattering particles perturbation theory is not applicable anymore, and phenomenological methods are used to describe the physics in this regime. The ATLAS experiment at the Large Hadron Collider, LHC, provides the possibility to analyze QCD processes at both ends of the momentum scale. Two measurements are presented in this thesis, emphasizing one of the two regimes each: The measurement of charged-particle event shape variables in inelastic proton-proton collisions at a center-of-mass energy of √(s)=7 TeV analyses the transverse momentum flow and structure of hadronic events. Due to the, on average, low momentum transfer, predictions of these events are mainly driven by non-perturbative models. Three event shapes are studied: The transverse thrust, the thrust minor and the transverse sphericity. Data recorded during low pile-up beam conditions in early 2010, corresponding to an integrated luminosity of 168 μb, is analyzed. Charged particles with a transverse momentum above 500 MeV are used to compute the event shape variables. In addition to differential event shape distributions in pT of the highest-transverse-momentum particle, the evolution of each event shape variable as a function of charged particle multiplicity and summed transverse momentum is presented. Predictions from different Monte Carlo models are compared with data and they show significant deviations from data. Using the results to tune the free parameters of the phenomenological models can improve future Monte Carlo predictions and give additional insight to the non-perturbative part of the QCD. The measurement of the double-differential dijet cross section as function of the dijet mass and rapidity
Deta, U. A., E-mail: utamaalan@yahoo.co.id [Theoretical Physics Group, Physics Department of Post Graduate Program, Sebelas Maret University, Jl. Ir. Sutami 36A, Surakarta 57126, Indonesia and Physics Department, State University of Surabaya, Jl. Ketintang, Surabaya 60231 (Indonesia); Suparmi,; Cari,; Husein, A. S.; Yuliani, H.; Khaled, I. K. A.; Luqman, H.; Supriyanto [Theoretical Physics Group, Physics Department of Post Graduate Program, Sebelas Maret University, Jl. Ir. Sutami 36A, Surakarta 57126 (Indonesia)
2014-09-30
The Energy Spectra and Wave Function of Schrodinger equation in D-Dimensions for trigonometric Rosen-Morse potential were investigated analytically using Nikiforov-Uvarov method. This potential captures the essential traits of the quark-gluon dynamics of Quantum Chromodynamics. The approximate energy spectra are given in the close form and the corresponding approximate wave function for arbitrary l-state (l ≠ 0) in D-dimensions are formulated in the form of differential polynomials. The wave function of this potential unnormalizable for general case. The wave function of this potential unnormalizable for general case. The existence of extra dimensions (centrifugal factor) and this potential increase the energy spectra of system.
The Energy Spectra and Wave Function of Schrodinger equation in D-Dimensions for trigonometric Rosen-Morse potential were investigated analytically using Nikiforov-Uvarov method. This potential captures the essential traits of the quark-gluon dynamics of Quantum Chromodynamics. The approximate energy spectra are given in the close form and the corresponding approximate wave function for arbitrary l-state (l ≠ 0) in D-dimensions are formulated in the form of differential polynomials. The wave function of this potential unnormalizable for general case. The wave function of this potential unnormalizable for general case. The existence of extra dimensions (centrifugal factor) and this potential increase the energy spectra of system
Deta, U. A.; Suparmi, Cari, Husein, A. S.; Yuliani, H.; Khaled, I. K. A.; Luqman, H.; Supriyanto
2014-09-01
The Energy Spectra and Wave Function of Schrodinger equation in D-Dimensions for trigonometric Rosen-Morse potential were investigated analitically using Nikiforov-Uvarov method. This potential captures the essential traits of the quark-gluon dynamics of Quantum Chromodynamics. The approximate energy spectra are given in the close form and the corresponding approximate wave function for arbitary l-state (l ≠ 0) in D-dimensions are formulated in the form of diferential polynomials. The wave function of this potential unnormalizable for general case. The wave function of this potential unnormalizable for general case. The existence of extra dimensions (centrifugal factor) and this potential increase the energy spectra of system.
The future CERN collider (LHC) has a fantastic potential of discovery, provided quantum chromodynamics can be quantitatively predicted. To do so, it is necessary to work at NLO approximation in order to reduce the dependence of the -cross-section on- the non-physical scales. To obtain results in this approximation, one has to calculate the cross-sections of the partonic subprocesses contributing to the studied reaction at the lowest order, and also the virtual corrections (loop corrections) and the real corrections. The calculation of the virtual corrections remains very complicated if the number of external particles is greater than four or if the external (internal) particles are massive. in this thesis, an automatic method which enables to calculate one loop diagrams with five external legs and which can be generalized to the case of massive particles is presented. In a first part, we describe different tools and methods necessary to such calculations. We then apply -them to the calculation of the gg →γγ g reaction, which interests the ATLAS and CMS experimentalists as the background for the Higgs boson search. We also give the explicit result for this amplitude for each helicity configuration in a compact form and a clearly gauge invariant representation. We finally present a phenomenological study of this reaction. (author)
Marquet, C
2006-09-15
When probing small distances inside a hadron, one can resolve its partonic constituents: quarks and gluons that obey the laws of perturbative Quantum Chromodynamics (QCD). This substructure reveals itself in hadronic collisions characterized by a large momentum transfer: in such collisions, a hadron acts like a collection of partons whose interactions can be described in QCD. In a collision at moderate energy, a hadron looks dilute and the partons interact incoherently. As the collision energy increases, the parton density inside the hadron grows. Eventually, at some energy much bigger than the momentum transfer, one enters the saturation regime of QCD: the gluon density has become so large that collective effects are important. We introduce a formalism suitable to study hadronic collisions in the high-energy limit in QCD, and the transition to the saturation regime. In this framework, we derive known results that are needed to present our personal contributions and we compute different cross-sections in the context of hard diffraction and particle production. We study the transition to the saturation regime as given by the Balitsky-Kovchegov equation. In particular we derive properties of its solutions.We apply our results to deep inelastic scattering and show that, in the energy range of the HERA collider, the predictions of high-energy QCD are in good agreement with the data. We also consider jet production in hadronic collisions and discuss the possibility to test saturation at the Large Hadron Collider. (author)
Chiral and deconfinement phase transitions in N{sub f}=2 and N{sub f}=2+1 quantum chromodynamics
Luecker, Jan
2013-07-15
In this thesis, we investigate the phase structure of quantum chromodynamics (QCD) in the framework of Dyson-Schwinger equations (DSEs). The aim is to study the chiral and deconfinement phase transitions at finite chemical potential. To this end, we employ and test a novel truncation scheme for the quark and gluon Dyson-Schwinger equations. We develop our truncation in three steps. To begin with, we use a quenched gluon propagator from lattice Yang-Mills theory. To account for unquenching, we then add the quark loop in the gluon DSE, firstly with bare quarks and in the final version of our truncation with fully dressed quarks. In the last step it is also possible to take into account the coupling of light and strange quarks. In effective models, fermionic fluctuations have been shown to move the critical end-point to large densities. We confirm this finding within our truncation for the unquenched gluon. However, this effect is suppressed once the full non-perturbative quark in the quark loop is taken into account. For the confinement/deconfinement transition we investigate three order parameters that are accessible from the quark and gluon propagators. These are the dressed Polyakov loop, the Polyakov-loop potential and positivity violations in the quark propagator. From both Polyakov-loop related order parameters, we find that the deconfinement transition can always be found in vicinity of the chiral transition. Especially at the critical end-point the phase transitions coincide. We also find that signals of positivity violations in the quark propagator vanish at the chiral transition for the two-flavour case. However, with 2+1 flavours, we find a region at large density where chiral symmetry is restored but positivity is violated. This requires further investigations. Finally, we improve our truncation by considering the back-reaction of pions in a model that has been developed in previous work. Within this model we find only a small impact on the phase
Polarization phenomena in quantum chromodynamics
The author discusses a number of interrelated hadronic spin effects which test fundamental features of perturbative and non-perturbative QCD. For example, the anomalous magnetic moment of the proton and the axial coupling gA on the nucleon are shown to be related to each other for fixed proton radius, independent of the form of the underlying three-quark relativistic quark wavefunction. The renormalization scale and scheme ambiguities for the radiative corrections to the Bjorken sum rule for the polarized structure functions can be eliminated by using commensurate scale relations with other observables. Other examples include (a) new constraints on the shape and normalization of the polarized quark and gluon structure functions of the proton at large and small xbj; (b) consequences of the principle of hadron helicity retention in high xF inclusive reactions; (c) applications of hadron helicity conservation to high momentum transfer exclusive reactions; and (d) the dependence of nuclear structure functions and shadowing on virtual photon polarization. He also discusses the implications of a number of measurements which are in striking conflict with leading-twist perturbative QCD predictions, such as the extraordinarily large spin correlation ANN observed in large angle proton-proton scattering, the anomalously large ρπ branching ratio of the J/ψ, and the rapidly changing polarization dependence of both J/ψ and continuum lepton pair hadroproduction observed at large xF. The azimuthal angular dependence of the Drell-Yan process is shown to be highly sensitive to the projectile distribution amplitude, the fundamental valence light-cone wavefunction of the hadron
Testing quantum chromodynamics in electroproduction
The exclusive channels in electroproduction are discussed. The study of color transparency, the formation zone, and other novel aspects of QCD by measuring exclusive reactions inside nuclear targets is covered. Diffractive electroproduction channels are discussed, and exclusive nuclear processes in QCD are examined. Non-additivity of nuclear structure functions (EMC effect) is also discussed, as well as jet coalescence in electroproduction
Quantum chromodynamics at high energy
Kovchegov, Yuri V
2012-01-01
Filling a gap in the current literature, this book is the first entirely dedicated to high energy QCD including parton saturation. It presents groundbreaking progress on the subject and describes many of the problems at the forefront of research, bringing postgraduate students, theorists and advanced experimentalists up to date with the current status of the field. A broad range of topics in high energy QCD are covered, most notably on the physics of parton saturation and the Color Glass Condensate (CGC). The material is presented in a pedagogical way, with numerous examples and exercises. Discussion ranges from the quasi-classical McLerran–Venugopalan model to the linear and non-linear BFKL/BK/JIMWLK small-x evolution equations. The authors adopt both a theoretical and experimental outlook and present the physics of strong interactions in a universal way, making it useful to physicists from various sub-communities and applicable to processes studied at high energy accelerators around the world.
Polarization phenomena in quantum chromodynamics
Brodsky, S.J.
1994-03-01
The author discusses a number of interrelated hadronic spin effects which test fundamental features of perturbative and non-perturbative QCD. For example, the anomalous magnetic moment of the proton and the axial coupling g{sub A} on the nucleon are shown to be related to each other for fixed proton radius, independent of the form of the underlying three-quark relativistic quark wavefunction. The renormalization scale and scheme ambiguities for the radiative corrections to the Bjorken sum rule for the polarized structure functions can be eliminated by using commensurate scale relations with other observables. Other examples include (a) new constraints on the shape and normalization of the polarized quark and gluon structure functions of the proton at large and small x{sub bj}; (b) consequences of the principle of hadron helicity retention in high x{sub F} inclusive reactions; (c) applications of hadron helicity conservation to high momentum transfer exclusive reactions; and (d) the dependence of nuclear structure functions and shadowing on virtual photon polarization. He also discusses the implications of a number of measurements which are in striking conflict with leading-twist perturbative QCD predictions, such as the extraordinarily large spin correlation A{sub NN} observed in large angle proton-proton scattering, the anomalously large {rho}{pi} branching ratio of the J/{psi}, and the rapidly changing polarization dependence of both J/{psi} and continuum lepton pair hadroproduction observed at large x{sub F}. The azimuthal angular dependence of the Drell-Yan process is shown to be highly sensitive to the projectile distribution amplitude, the fundamental valence light-cone wavefunction of the hadron.
Working group report: Quantum chromodynamics
V Ravindra; Pankaj Agrawal; Rahul Basu; Satyaki Bhattacharya; J Blümlein; V Del Duca; R Harlander; D Kosower; Prakash Mathews; Anurag Tripathi
2006-11-01
This is the report of the subgroup QCD of Working Group-4 at WHEPP-9. We present the activities that had taken place in the subgroup and report some of the partial results arrived at following the discussion at the working group meetings.
Exclusive processes in quantum chromodynamics
Large momentum transfer exclusive processes and the short distance structure of hadronic wave functions can be systematically analyzed within the context of perturbative QCD. Predictions for meson form factors, two-photon processes γγ → M anti M, hadronic decays of heavy quark systems, and a number of other related QCD phenomena are reviewed
Two topics in quantum chromodynamics
The two topics are (1) estimates of perturbation theory coefficients for R(e+e- → hadrons), and (2) the virtual-photon structure function, with emphasis on the analytic behavior in its squared mass. 20 refs., 4 figs., 2 tabs
Quantum chromodynamics at hadron colliders
Vittorio Del Duca
2006-11-01
QCD is an extensively developed and tested gauge theory, which models the strong interactions in the high-energy regime. In this talk, I shall review the considerable progress which has been achieved in the last few years in the most actively studied QCD topics: Monte Carlo models, higher-order corrections, and parton distribution functions. Thanks to that, QCD in the high-energy regime is becoming more and more an essential precision tool kit to analyse Higgs and new physics scenarios at the LHC.
Antiproton annihilation in quantum chromodynamics
Anti-proton annihilation has a number of important advantages as a probe of QCD in the low energy domain. Exclusive reaction in which complete annihilation of the valance quarks occur. There are a number of exclusive and inclusive /bar p/ reactions in the intermediate momentum transfer domain which provide useful constraints on hadron wavefunctions or test novel features of QCD involving both perturbative and nonperturbative dynamics. Inclusive reactions involving antiprotons have the advantage that the parton distributions are well understood. In these lectures, I will particularly focus on lepton pair production /bar p/A → /ell//bar /ell//X as a means to understand specific nuclear features in QCD, including collision broadening, breakdown of the QCD ''target length condition''. Thus studies of low to moderate energy antiproton reactions with laboratory energies under 10 GeV could give further insights into the full structure of QCD. 112 refs., 40 figs
Phase transitions in quantum chromodynamics
Meyer-Ortmanns, H
1996-01-01
The current understanding of finite temperature phase transitions in QCD is reviewed. A critical discussion of refined phase transition criteria in numerical lattice simulations and of analytical tools going beyond the mean-field level in effective continuum models for QCD is presented. Theoretical predictions about the order of the transitions are compared with possible experimental manifestations in heavy-ion collisions. Various places in phenomenological descriptions are pointed out, where more reliable data for QCD's equation of state would help in selecting the most realistic scenario among those proposed. Unanswered questions are raised about the relevance of calculations which assume thermodynamic equilibrium. Promising new approaches to implement nonequilibrium aspects in the thermodynamics of heavy-ion collisions are described.
Hoecker, A. [Paris-11 Univ., 91 - Orsay (France). Lab. de l' Accelerateur Lineaire]|[Universite de Paris Sud, 91 - Orsay (France)
1997-04-18
This thesis presents measurements of the {tau} vector (V) and axial-vector (A) hadronic spectral functions and phenomenological studies in the framework of quantum chromodynamics (QCD). Using the hypothesis of conserved vector currents (CVC), the dominant two- and four-pion vector spectral functions are compared to the corresponding cross sections from e{sup +}e{sup -} annihilation. A combined fit of the pion form factor from {tau} decays and e{sup +}e{sup -} data is performed using different parametrizations. The mass and the width of the {rho}{sup {+-}}(770) and the {rho}{sup 0}(770) are separately determined in order to extract possible isospin violating effects. The mass and width differences are measured to be M{sub {rho}{sup {+-}}{sub (770)} - M{sub {rho}{sup 0}}{sub (770)}=(0.0{+-}1.0) MeV/c{sup 2} and {gamma}{sub {rho}{sup {+-}}{sub (770)} - {gamma}{sub {rho}{sup 0}}{sub (770)}=(0.1 {+-} 1.9) MeV/c{sup 2}. Several QCD chiral sum rules involving the difference (V - A) of the spectral functions are compared to their measurements. The Borel-transformed Das-Mathur-Okubo sum rule is used to measure the pion polarizability to be {alpha}{sub E}=(2.68{+-}0.91) x 10{sup -4} fm{sup 3}. The {tau} vector and axial-vector hadronic widths and certain spectral moments are exploited to measure {alpha}{sub s} and non-perturbative contributions at the {tau} mass scale. The best, and experimentally and theoretically most robust, determination of {alpha}{sub s}(M{sub {tau}}) is obtained from the inclusive (V + A) fit that yields {alpha}{sub s}(M{sub {tau}})= 0.348{+-}0.017 giving {alpha}{sub s}(M{sub Z})=0.1211 {+-} 0.0021 after the evolution to the mass of the Z boson. The approach of the Operator Product Expansion (OPE) is tested experimentally by means of an evolution of the {tau} hadronic width to masses smaller that the {tau} mass. Using the difference (V - A) of the spectral functions allows one to directly measure the dominant non-perturbative OPE dimension to be D=6
Perez Ramos, R
2006-09-15
We exactly calculate the double and simple inclusive transverse momentum (kt) distributions and the 2-particle momentum correlations inside high energy hadronic jets at the Modified Leading Logarithmic Approximation (MLLA) of Quantum Chromodynamics. We first obtain the exact solution of the evolution equations at 'small x', which we calculate at the so called 'limiting spectrum'. We then generalize this approximation by performing the steepest descent evaluation. Our predictions are in good agreement with data from Tevatron and improve those which have been obtained in the past. The comparison with forthcoming data (Tevatron, LHC) will further test the hypothesis of Local Hadron Parton Duality, and the eventual need to incorporate next-MLLA corrections. (authors)
Quark confinement physics from quantum chromodynamics
We show the construction of the dual superconducting theory for the confinement mechanism from QCD in the maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. We find that essence of infrared abelian dominance is naturally understood with the off-diagonal gluon mass moff ≅ 1.2GeV induced by the MA gauge fixing. In the MA gauge, the off-diagonal gluon amplitude is forced to be small, and the off-diagonal gluon phase tends to be random. As the mathematical origin of abelian dominance for confinement, we demonstrate that the strong randomness of the off-diagonal gluon phase leads to abelian dominance for the string tension. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system. We investigate the monopole-current system in the MA gauge by analyzing the dual gluon field Bμ. We evaluate the dual gluon mass as mB = 0.4 ∼ 0.5GeV in the infrared region, which is the lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Owing to infrared abelian dominance and infrared monopole condensation, QCD in the MA gauge is describable with the dual Ginzburg-Landau theory
Light-cone quantization of quantum chromodynamics
We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, ''discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism
Large- quantum chromodynamics and harmonic sums
Eduardo De Rafael
2012-06-01
In the large- limit of QCD, two-point functions of local operators become harmonic sums. I review some properties which follow from this fact and which are relevant for phenomenological applications. This has led us to consider a class of analytic number theory functions as toy models of large- QCD which also is discussed.
Light-cone quantization of quantum chromodynamics
Brodsky, S.J. (Stanford Linear Accelerator Center, Menlo Park, CA (USA)); Pauli, H.C. (Max-Planck-Institut fuer Kernphysik, Heidelberg (Germany, F.R.))
1991-06-01
We discuss the light-cone quantization of gauge theories from two perspectives: as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions at fixed light cone time provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive weak decays of heavy hadrons, and intrinsic heavy-quark contributions to structure functions. A general nonperturbative method for numerically solving quantum field theories, discretized light-cone quantization,'' is outlined and applied to several gauge theories, including QCD in one space and one time dimension, and quantum electrodynamics in physical space-time at large coupling strength. The DLCQ method is invariant under the large class of light-cone Lorentz transformations, and it can be formulated such at ultraviolet regularization is independent of the momentum space discretization. Both the bound-state spectrum and the corresponding relativistic light-cone wavefunctions can be obtained by matrix diagonalization and related techniques. We also discuss the construction of the light-cone Fock basis, the structure of the light-cone vacuum, and outline the renormalization techniques required for solving gauge theories within the light-cone Hamiltonian formalism.
Quantum chromodynamics (QCD) and collider physics
Ellis, R.K. (Fermi National Accelerator Lab., Batavia, IL (USA)); Stirling, W.J. (Durham Univ. (UK))
1990-08-14
This report discusses: fundamentals of perturbative QCD; QCD in e{sup +}e{sup {minus}} {yields} hadrons; deep inelastic scattering and parton distributions; the QCD parton model in hadron-hadron collisions; large p{sub T} jet production in hadron-hadron collisions; the production of vector bosons in hadronic collisions; and the production of heavy quarks.
Quantum chromodynamics near the confinement limit
Quigg, C.
1985-09-01
These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment.
Higher order corrections in perturbative quantum chromodynamics
W L Van Neerven
2000-07-01
We present some techniques which have been developed recently or in the recent past to compute Feynman graphs beyond one-loop order. These techniques are useful to compute the three-loop splitting functions in QCD and to obtain the complete second order QED corrections to Bhabha scattering.
On de-globalization in quantum chromodynamics
The recent discovery and resummation of a class of single logarithmic effects (non-global logs), has a significant impact on several QCD observables ranging from the classic Sterman-Weinberg jet definition to currently studied event shapes and rapidity gap observables. The discovery of the above effects overturns, for example, the common wisdom that hadronic energy flow in limited inter-jet regions is dictated primarily by the colour flow of the underlying hard partonic subprocess. We discuss some features of non-global logs and the rapid progress being made in estimating and controlling such corrections. (author)
Quark Confinement Physics from Quantum Chromodynamics
Suganuma, H; Tanaka, A; Ichie, H
2016-01-01
We show the construction of the dual superconducting theory for the confinement mechanism from QCD in the maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. We find that essence of infrared abelian dominance is naturally understood with the off-diagonal gluon mass $m_{\\rm off} \\simeq 1.2 {\\rm GeV}$ induced by the MA gauge fixing. In the MA gauge, the off-diagonal gluon amplitude is forced to be small, and the off-diagonal gluon phase tends to be random. As the mathematical origin of abelian dominance for confinement, we demonstrate that the strong randomness of the off-diagonal gluon phase leads to abelian dominance for the string tension. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system. We investigate the monopole-current system in the MA gauge by analyzing the dual gluon field $B_\\mu$. We evaluate the dual gluon mass as $m_B = 0.4 \\sim$ 0.5GeV in the infrared region, which is the lattice-QCD evidence of the dual Higgs mechan...
Calculations in external fields in quantum chromodynamics
The technique of calculation of operator expansion coefficients is reviewed. The main emphasis is put on gluon operators which appear in expansion of n-point functions induced by colourless quark currents. Two convenient schemes are discussed in detail: the abstract operator method and the method based on the Fock-Schwinger gauge for the vacuum gluon field. A large number of instructive examples important from the point of view of physical applications is considered
Unification of Einstein's Gravity with Quantum Chromodynamics
Sarfatti, Jack
2010-02-01
The four tetrad and six spin-connection Cartan 1-forms of Einstein's GeoMetroDynamic (GMD) field emerge from the eight virtual gluon macro-quantum coherent QCD post-inflation vacuum condensates that form in the inflationary phase transition. This joint emergence of gravity and the strong force is similar to the emergence of irrotational superflow with vortex defects in liquid helium below the Lambda Point. Repulsive dark energy is from the residual random virtual bosons that did not cohere in the moment of inflation. Similarly, attractive dark matter is from the residual random virtual fermion-antifermion pairs. Therefore, I predict that the LHC will not detect any on-mass-shell real particles that can explain φDM˜0.23. As first suggested by Abdus Salam (f-gravity) the low energy tail of the nuclear force can be explained as strong short-range Yukawa gravity. QCD's IR confinement and UV asymptotic freedom are elementary consequences in this simple model. )
Duality and effective amplitudes in quantum chromodynamics
This work is an attempt to relate the partonic and hadronic phases of strong interactions by means of a model of effective string amplitudes which take into account color coherence without the need to restrict the phase-space. The basic idea of this approach is to construct, from open superstrings, string amplitudes which give, at the zero slope limit, QCD amplitudes. The running parameters (coupling and slope) of the model are constrained by perturbative QCD and by the consistency of string quantization. When the running slope becomes equal to the hadronic one, the model can be used in the hadronic sector. This approach could provide some hints about the effective string theory of QCD, and a better understanding of the parton-hadron duality
Quantum chromodynamics results from HERA and JLAB
Katja Krüger
2012-10-01
Recent QCD results from electron–proton interactions at HERA and JLAB are presented. Inclusive cross-section measurements as well as studies of the hadronic final state like jet production or the production of heavy quarks are discussed. The results are compared with perturbative QCD predictions and their impact on the determination of the parton density functions of the proton as well as of the strong coupling α s is discussed.
Introduction to quantum chromodynamics at hadron colliders
William B Kilgore
2011-05-01
A basic introduction to the application of QCD at hadron colliders is presented. I brieﬂy review the phenomenological and theoretical origins of QCD, and then discuss factorization and infrared safety, parton distributions, the computation of hard scattering amplitudes and applications of perturbative QCD.
Understanding QCD [Quantum Chromodynamics] at colliders
We examine Drell-Yan μ-pair production and heavy quark pair production, and demonstrate how to implement precise comparisons between the theoretical predictions of QCD and the experimental observables. Specifically, we have dealt with theoretical uncertainties arising from higher order corrections, unknown small-χ behavior, and the unknown gluon distribution. We indicate how the above processes can provide discriminating tests of the theory in the kinematic regimes which will soon be investigated by the Tevatron I and HERA facilities. 8 refs., 6 figs
Quaternion Octonion Reformulation of Quantum Chromodynamics
Pushpa,; Bisht, P. S.; Li, Tianjun; Negi, O. P. S.
2010-01-01
We have made an attempt to develop the quaternionic formulation of Yang - Mill's field equations and octonion reformulation of quantum chromo dynamics (QCD). Starting with the Lagrangian density, we have discussed the field equations of SU(2) and SU(3) gauge fields for both cases of global and local gauge symmetries. It has been shown that the three quaternion units explain the structure of Yang- Mill's field while the seven octonion units provide the consistent structure of SU(3)_{C} gauge s...
On de-globalization in quantum chromodynamics
Das-Gupta, M
2004-01-01
The recent discovery and resummation of a class of single-logarithmic effects (non-global logs), has a significant impact on several QCD observables ranging from the classic Sterman-Weinberg jet definition to currently studied event shapes and rapidity gap observables. The discovery of the above effects overturns, for example, the common wisdom that hadronic energy flow in limited interjet regions is dictated primarily by the colour flow in the underlying hard partonic subprocess. We discuss some features of non-global logs and the rapid progress being made in estimating and controlling such corrections.
From moments to functions in quantum chromodynamics
Single-scale quantities, like the QCD anomalous dimensions andWilson coefficients, obey difference equations. Therefore their analytic form can be determined from a finite number of moments. We demonstrate this in an explicit calculation by establishing and solving large scale recursions by means of computer algebra for the anomalous dimensions and Wilson coefficients in unpolarized deeply inelastic scattering from their Mellin moments to 3-loop order. (orig.)
From moments to functions in quantum chromodynamics
Bluemlein, Johannes; Klein, Sebastian [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany); Kauers, Manuel; Schneider, Carsten [Johannes Kepler Univ., Linz (Austria). Research Inst. for Symbolic Computation
2009-02-15
Single-scale quantities, like the QCD anomalous dimensions andWilson coefficients, obey difference equations. Therefore their analytic form can be determined from a finite number of moments. We demonstrate this in an explicit calculation by establishing and solving large scale recursions by means of computer algebra for the anomalous dimensions and Wilson coefficients in unpolarized deeply inelastic scattering from their Mellin moments to 3-loop order. (orig.)
Quantum chromodynamics studies at LEP2
Sunanda Banerjee
2000-07-01
Several studies have been made to the hadronic ﬁnal states in +- collisions at LEP. Studies of the annihilation process at LEP2 have given rise to results on jet rate, event shape, heavy ﬂavour production, inclusive momentum spectra, Bose–Einstein correlation and colour reconnection effects. Event shape studies have given rise to accurate determination of the strong coupling constant s using $\\mathcal{O}(^{2}_{s})$ with resummed leading and next-to-leading log calculation and also with power law corrections. Studies of 2-photon processes have yielded results on cross-section, heavy ﬂavour production, photon structure function and ** scattering.
Lattice quantum chromodynamics with approximately chiral fermions
Hierl, Dieter
2008-05-15
In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the {theta}{sup +} pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)
Lattice quantum chromodynamics with approximately chiral fermions
In this work we present Lattice QCD results obtained by approximately chiral fermions. We use the CI fermions in the quenched approximation to investigate the excited baryon spectrum and to search for the Θ+ pentaquark on the lattice. Furthermore we developed an algorithm for dynamical simulations using the FP action. Using FP fermions we calculate some LECs of chiral perturbation theory applying the epsilon expansion. (orig.)
Case studies in perturbative quantum chromodynamics
A few aspects of QCD are discussed, beginning with a discussion of the ingredients of QCD and their observational basis. A pedagogical treatment of scaling violations is presented and the argument is presented that while entirely consistent with QCD, the phenomenological situation is clouded by the potentially crucial role of higher twist effects in the theory. Some explicit calculations of higher twist effects are presented
Quantum chromodynamics near the confinement limit
These nine lectures deal at an elementary level with the strong interaction between quarks and its implications for the structure of hadrons. Quarkonium systems are studied as a means for measuring the interquark interaction. This is presumably (part of) the answer a solution to QCD must yield, if it is indeed the correct theory of the strong interactions. Some elements of QCD are reviewed, and metaphors for QCD as a confining theory are introduced. The 1/N expansion is summarized as a way of guessing the consequences of QCD for hadron physics. Lattice gauge theory is developed as a means for going beyond perturbation theory in the solution of QCD. The correspondence between statistical mechanics, quantum mechanics, and field theory is made, and simple spin systems are formulated on the lattice. The lattice analog of local gauge invariance is developed, and analytic methods for solving lattice gauge theory are considered. The strong-coupling expansion indicates the existence of a confining phase, and the renormalization group provides a means for recovering the consequences of continuum field theory. Finally, Monte Carlo simulations of lattice theories give evidence for the phase structure of gauge theories, yield an estimate for the string tension characterizing the interquark force, and provide an approximate description of the quarkonium potential in encouraging good agreement with what is known from experiment
Mahmoudi, F
2004-06-01
The future CERN collider (LHC) has a fantastic potential of discovery, provided quantum chromodynamics can be quantitatively predicted. To do so, it is necessary to work at NLO approximation in order to reduce the dependence of the -cross-section on- the non-physical scales. To obtain results in this approximation, one has to calculate the cross-sections of the partonic subprocesses contributing to the studied reaction at the lowest order, and also the virtual corrections (loop corrections) and the real corrections. The calculation of the virtual corrections remains very complicated if the number of external particles is greater than four or if the external (internal) particles are massive. in this thesis, an automatic method which enables to calculate one loop diagrams with five external legs and which can be generalized to the case of massive particles is presented. In a first part, we describe different tools and methods necessary to such calculations. We then apply -them to the calculation of the gg {yields}{gamma}{gamma} g reaction, which interests the ATLAS and CMS experimentalists as the background for the Higgs boson search. We also give the explicit result for this amplitude for each helicity configuration in a compact form and a clearly gauge invariant representation. We finally present a phenomenological study of this reaction. (author)
Fermions in light front transverse lattice quantum chromodynamics
Dipankar Chakrabarti; Asit K De; A Harindranath
2003-11-01
We brieﬂy describe motivations for studying transverse lattice QCD. Presence of constraint equation for fermion ﬁeld on the light front allows different methods to put fermions on a transverse lattice. We summarize our numerical investigation of two approaches using (a) forward and backward derivatives and (b) symmetric derivatives.
Quark confinement and color monopoles in quantum chromodynamics
We show the construction of the dual superconducting theory for the confinement mechanism from QCD in the maximally abelian (MA) gauge using the lattice QCD Monte Carlo simulation. We find that essence of infrared abelian dominance is naturally understood with the off-diagonal gluon mass moff ≅ 1.2 GeV induced by the MA gauge fixing. In the MA gauge, the off-diagonal gluon amplitude is forced to be small, and the off-diagonal gluon phase tends to be random. As the mathematical origin of abelian dominance for confinement, we demonstrate that the strong randomness of the off-diagonal gluon phase leads to abelian dominance for the string tension. In the MA gauge, there appears the macroscopic network of the monopole world-line covering the whole system. We investigate the monopole-current system in the MA gauge by analyzing the dual gluon field Bμ. We evaluate the dual gluon mass as mB = 0.4 ∼ 0.5 GeV in the infrared region, which is the lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Owing to infrared abelian dominance and infrared monopole condensation, QCD in the MA gauge is describable with the dual Ginzburg-Landau theory. (author)
Inclusive and Exclusive Compton Processes in Quantum Chromodynamics
Ales Psaker
2005-12-31
In our work, we describe two types of Compton processes. As an example of an inclusive process, we consider the high-energy photoproduction of massive muon pairs off the nucleon. We analyze the process in the framework of the QCD parton model, in which the usual parton distributions emerge as a tool to describe the nucleon in terms of quark and gluonic degrees of freedom. To study its exclusive version, a new class of phenomenological functions is required, namely, generalized parton distributions. They can be considered as a generalization of the usual parton distributions measured in deeply inelastic lepton-nucleon scattering. Generalized parton distributions (GPDs) may be observed in hard exclusive reactions such as deeply virtual Compton scattering. We develop an extension of this particular process into the weak interaction sector. We also investigate a possible application of the GPD formalism to wide-angle real Compton scattering.
Connections between quantum chromodynamics and condensed matter physics
Shailesh Chandrasekharan
2003-11-01
Features of QCD can be seen qualitatively in certain condensed matter systems. Recently some of the analyses that originated in condensed matter physics have found applications in QCD. Using examples we discuss some of the connections between the two ﬁelds and show how progress can be made by exploiting this connection. Some of the challenges that remain in the two ﬁelds are quite similar. We argue that recent algorithmic developments call for optimism in both ﬁelds.
Discussion of Various Susceptibilities within Thermal and Dense Quantum Chromodynamics
Xu, Shu-Sheng; Shi, Yuan-Mei; Yang, You-Chang; Cui, Zhu-Fang; Zong, Hong-Shi
2015-12-01
Not Available Supported by the National Natural Science Foundation of China under Grant Nos 11275097, 11475085, 11535005, and 11265017, the Jiangsu Planned Projects for Postdoctoral Research Funds under Grant No 1402006C, the China Postdoctoral Science Foundation under Grant No 2015M571728, the Natural Science Foundation of Jiangsu Province under Grant No BK20130078, and the Guizhou-Provincial Outstanding Youth Science and Technology Talent Cultivation Object Special Funds under Grant No QKHRZ(2013)28.
Quantum chromodynamics as a microscopic theory of superfluidity
It is shown that the hypothesis of the singular Bose-condensate and collective excitation can be realized in the Yang-Mills quantum theory at a definite choice of the dynamical variables. This idea is developed by using the analogy with the microscopic theory of superfluidity. The spectrum of quasiparticle excitations is obtained for the Bose-condensate in the class of cylindrically symmetric functions. It is shown that nonobservability of coloured quasiparticles can be a result of superfluid properties of vortices of the Bose-condensate. The comparison with superfluid helium in a rotating bucket has shown that it may happen to be impossible theoretically, without experimental facts, to define the parameters of gluon ''vortices'', i.e., the dimension and spatial configuration of gluon bags
Precision tests of quantum chromodynamics and the standard model
The authors discuss three topics relevant to testing the Standard Model to high precision: commensurate scale relations, which relate observables to each other in perturbation theory without renormalization scale or scheme ambiguity, the relationship of compositeness to anomalous moments, and new methods for measuring the anomalous magnetic and quadrupole moments of the W and Z
Quantum Chromodynamics and nuclear physics at extreme energy density
This report discusses research in the following topics: Hadron structure physics; relativistic heavy ion collisions; finite- temperature QCD; real-time lattice gauge theory; and studies in quantum field theory
Large-transverse-momentum correlations in quantum chromodynamics
The QCD approach to large-transverse-momentum inclusive single-hadron production is extended to two-hadron correlations. Detailed comparisons with the data on transverse-momentum sharing (x sub(e)) distributions are presented; it is shown that the scale violations in the parton fragmentation functions are of essential importance in obtaining agreement with experiment. Opposite-side rapidity distributions are also presented and the question of back-to-back effects is discussed. It is concluded that, on the whole, QCD adequately describes the data. (author)
Precision tests of quantum chromodynamics and the standard model
Brodsky, S.J.; Lu, H.J.
1995-06-01
The authors discuss three topics relevant to testing the Standard Model to high precision: commensurate scale relations, which relate observables to each other in perturbation theory without renormalization scale or scheme ambiguity, the relationship of compositeness to anomalous moments, and new methods for measuring the anomalous magnetic and quadrupole moments of the W and Z.
Lattice quantum chromodynamics equation of state: A better differential method
Rajiv V Gavai; Sourendu Gupta; Swagato Mukherjee
2008-09-01
We propose a better differential method for the computation of the equation of state of QCD from lattice simulations. In contrast to the earlier differential method, our technique yields positive pressure for all temperatures including the temperatures in the transition region. Employing it on temporal lattices of 8, 10 and 12 sites and by extrapolating to zero lattice spacing we obtained the pressure, energy density, entropy density, specific heat and speed of sound in quenched QCD for 0.9 ≤ /c ≤ 3. At high temperatures comparisons of our results are made with those from the dimensional reduction approach and also with those from a conformal symmetric theory.
Quantum Chromodynamics and Other Field Theories on the Light Cone
Brodsky, S.; Pauli, H-C; Pinsky, S.
1997-01-01
We discuss the light-cone quantization of gauge theories as a calculational tool for representing hadrons as QCD bound-states of relativistic quarks and gluons, and also as a novel method for simulating quantum field theory on a computer. The light-cone Fock state expansion of wavefunctions provides a precise definition of the parton model and a general calculus for hadronic matrix elements. We present several new applications of light-cone Fock methods, including calculations of exclusive we...
Photon pairs: Quantum chromodynamics continuum and the Higgs boson
Edmond L Berger
2007-11-01
A new QCD calculation is summarized for the transverse momentum distribution of photon pairs produced by QCD subprocesses, including all-orders soft-gluon resummation valid at next-to-next-to-leading logarithmic accuracy. Resummation is needed to obtain reliable predictions in the range of transverse momentum where the cross-section is the largest. Results are compared with data from the Fermilab Tevatron and predictions are made for the large hadron collider. The QCD continuum is shown to have a softer spectrum than the Higgs boson signal at the LHC.
Mechanical analog for a quantum-chromodynamic phase transition
Salomone, A.; Schechter, J.
1982-07-15
A simple mechanical model involving a pendulum and a spring is shown to give the same phase-transition behavior as that of either the effective chiral Lagrangian for one-flavor QCD or the massive Schwinger model. This model, which also has been studied in catastrophe theory, permits us to get a nice understanding of what at first appears to be a complicated system. We also construct and analyze a mechanical analog model for the two-flavor case. The latter has a similar behavior, in general, but does present some interesting new features. With this experience under our belts we are able to straightforwardly analyze the situation with an arbitrary number of flavors. We also discuss what the zero-flavor (i.e., pure QCD) limit of the effective Lagrangian should look like and give a formula for the ground-state energy as a function of the instanton angle theta. A number of other questions related to the QCD effective Lagrangian are investigated.
Sign-posting the phase diagram of quantum chromodynamics
Sourendu Gupta
2012-10-01
The good agreement between lattice predictions and data for the shape of the distribution of event-by-event fluctuations of the baryon number is discussed. Such comparisons can give fine probes of thermalization, and can be used to provide a direct determination of the cross-over temperature c QCD. The logic of these comparisons and the systematics involved are discussed. The same methods can be used to further explore the phase diagram.
Quantum chromodynamics with infinite number of vector mesons
It is supposed that families of vector mesons ρ, ψ, Υ contain an infinite number of resonances with gradually increasing widths. The asymptotic freedom requirement involves a relationship between the electronic width of a resonance and its mass derivative over the number. Using of this relationship it is shown that for the families of ψ and Υ mesons the moment from experimental function R(s)is egual to the sum of the moment from a bare quark loop and the edge term which arised from replacing of summation by integration. These equalities are fulfilled up to 1% for 60 moments in the ψ-meson family and up to 2% for 96 moments in the Υ-meson family. The electronic widths of the considered resonances and the ρ-meson mass are calculated
The critical point of quantum chromodynamics through lattice and experiment
Sourendu Gupta
2011-05-01
This talk discusses methods of extending lattice computations at ﬁnite temperature into regions of ﬁnite chemical potential, and the conditions under which such results from the lattice may be compared to experiments. Such comparisons away from a critical point are absolutely essential for quantitative use of lattice QCD in heavy-ion physics. An outline of various arguments which can then be used to locate the critical point is also presented.
Operator expansion in quantum chromodynamics beyond perturbation theory
The status of operator expansion at short distances is descussed within the frameworks of nonperturbatue QCD. The question of instanton effects is investigated in various aspects. Two-point functions induced by the gluonic currents are considered. It is shown that certain gluonic correlations vanish in the field of definite duality. It is proved that there does exist a very special relation between the expansion coefficients required by consistancy between instanton calculations and the general operator expansion. At last a certain modification of the naive version of operator expansion is proposed, which allows one to go beyond the critical power and construct, if necessary, an infinite series
Testing quantum chromodynamics in anti-proton reactions
Brodsky, S.J.
1987-10-01
An experimental program with anti-protons at intermediate energy can serve as an important testing ground for QCD. Detailed predictions for exclusive cross sections at large momentum transfer based on perturbative QCD and the QCD sum rule form of the proton distribution amplitude are available for anti p p ..-->.. ..gamma gamma.. for both real and virtual photons. Meson-pair and lepton-pair final states also give sensitive tests of the theory. The production of charmed hadrons in exclusive anti p p channels may have a non-negligible cross section. Anti-proton interactions in a nucleus, particularly J/psi production, can play an important role in clarifying fundamental QCD issues, such as color transparency, critical length phenomena, and the validity of the reduced nuclear amplitude phenomenology.
Quantum chromodynamics and hadronic interactions at short distances
A brief introduction to QCD and asymptotic freedom is given. A new method to avoid scheme and scale ambiguities in perturbative QCD predictions is discussed. A detailed discussion of light-cone perturbation theory and the Fock state expansion of hadronic wavefunctions is given. The QCD equation of motion is also discussed. Measures of the hadronic wavefunction (form factors, magnetic moments, etc.), and the QCD analysis of high momentum transfer exclusive processes are discussed. It is also shown how meson distribution amplitudes can be measured in γγ → M anti M reactions. The connection of the Fock state basis to leading and higher twist contributions to deep inelastic scattering is given. How many different QCD processes are interelated through the hadronic Fock states is discussed, and a novel type of QCD subprocess - direct coupled hadron-induced reactions is considered. A new prediction for the proton form factor is also given. Also, a simple phenomenology of hadron wavefunctions is introduced, and present constraints on the form and normalization of the valence meson and nucleon Fock states are discussed. An important conclusion is that the valence Fock state as defined at equal time or the light cone appears to have a significantly smaller radius than that of the physical hadron; higher Fock states thus play an essential role in low momentum transfer phenomenology. Applications to quark jet diffraction excitation and the hidden heavy quark Fock state structure of hadrons are also discussed. 83 references
Transverse spin and momentum correlations in quantum chromodynamics
Leonard P Gamberg
2009-01-01
The naive time reversal odd (`T-odd') parton distribution and fragmentation functions are explored. We use the spectator model framework to study flavour dependence of the Boer–Mulders $(h_{1}^{⊥})$ and Sivers $(f_{1\\text{T}}^{⊥})$ functions as well as the `T-even' but chiral odd function $h_{1\\text{L}}^{⊥}$. These transverse momentum-dependent parton distribution functions are of significance for the analysis of azimuthal asymmetries in semi-inclusive deep inelastic scattering, as well as for the overall physical understanding of the distribution of transversely polarized quarks in unpolarized hadrons. In this context we also consider the Collins mechanism and the fragmentation function $H_{1}^{⊥}$. As a by-product of this analysis we calculate the leading twist unpolarized cos(2) asymmetry, and sin(2) single spin asymmetry for a longitudinally polarized target in semi-inclusive deep inelastic scattering.
Chromodynamics of hadronic and nuclear reactions in the perturbative vacuum
In this report we discuss two topics which can be considered as positive practical tests of QCD: an estimate of the rise of total hadronic cross sections by means of QCD at the leading logarithm approximation and an estimate of the dependence in the atomic number of structure functions of nuclei (the so called EMC effect also by means of QCD)
Bag-model quantum chromodynamics for hyperons at low energy
In a non-perturbative bag model framework, gluon exchange which mediates quark exchange scattering in conjunction with quark interchange is shown to be the basis of the OBE interactions of hyperons at low energy. (orig.)
Bag-model quantum chromodynamics for hyperons at low energy
Weber, H. J.; Maslow, J. N.
1980-09-01
In a non-perturbative bag model framework, gluon exchange which mediates quark exchange scattering in conjunction with quark interchange is shown to be the basis of the OBE interactions of hyperons at low energy.
Open flavour charmed mesons in a quantum chromodynamics potential model
Krishna Kingkar Pathak; D K Choudhury
2012-12-01
We modify the mesonic wave function by using a short distance scale 0 in analogy with hydrogen atom and estimate the values of masses and decay constants of the open flavour charm mesons , $D_{s}$ and $B_{c}$ within the framework of a QCD potential model. We also calculate leptonic decay widths of these mesons to study branching ratios and lifetime. The results are in good agreement with experimental and other theoretical values.
Quantum chromodynamics and hadronic interactions at short distances
The main purpose of this lecture is to begin to extend QCD phenomenology by taking into account the physics of hadronic wavefunctions. The eventual goal is to obtain a parametrization of the wavefunctions which will bridge the gap between the non-perturbative and perturbative aspects of QCD. The lack of knowledge of hadronic matrix elements is the main difficulty in computing and normalizing dynamical higher twist contributions for many processes
Testing quantum chromodynamics in anti-proton reactions
An experimental program with anti-protons at intermediate energy can serve as an important testing ground for QCD. Detailed predictions for exclusive cross sections at large momentum transfer based on perturbative QCD and the QCD sum rule form of the proton distribution amplitude are available for anti p p → γγ for both real and virtual photons. Meson-pair and lepton-pair final states also give sensitive tests of the theory. The production of charmed hadrons in exclusive anti p p channels may have a non-negligible cross section. Anti-proton interactions in a nucleus, particularly J/psi production, can play an important role in clarifying fundamental QCD issues, such as color transparency, critical length phenomena, and the validity of the reduced nuclear amplitude phenomenology
Quantum chromodynamics and deep inelastic e - N scattering at TRISTAN
An introductory survey is given on the formulation of QCD in deep inelastic lepton-hadron scatterings. Typical predictions of QCD are presented in the kinematical region of TRISTAN, including detailed descriptions of the scaling violation, QCD correction to the current algebra sum rules, problem of quark masses and higher order effects. Some suggestions for experiments at TRISTAN are made. (author)
Microcanonical and hybrid simulations of lattice quantum chromodynamics with dynamical fermions
Lattice QCD is simulated using Microcanonical and Hybrid (Micro-canonical/Langevin) methods to facilitate the inclusion of dynamical fermions (quarks). We report on simulations with 4 flavors of light dynamical quarks on a 103 x 6 lattice to study the finite temperature deconfinement/chiral transition which should be observable in relativistic heavy ion collisions, as a function of quark mass. A first order transition is observed at large mass, weakens at intermediate mass and strengthens for very small quark mass
The SLUGGS survey: chromo-dynamical modelling of the lenticular galaxy NGC 1023
Cortesi, Arianna; Pota, Vincenzo; Foster, Caroline; Coccato, Lodovico; de Oliveira, Claudia Mendes; Forbes, Duncan A; Merrifield, Michael M; Bamford, Steven P; Romanowsky, Aaron J; Brodie, Jean P; Kartha, Sreeja S; Alabi, Adebusola B; Proctor, Robert N; Almeida, Andres
2015-01-01
Globular clusters (GCs) can be considered discrete, long-lived, dynamical tracers that retain crucial information about the assembly history of their parent galaxy. In this paper, we present a new catalogue of GC velocities and colours for the lenticular galaxy NGC 1023, we study their kinematics and spatial distribution, in comparison with the underlying stellar kinematics and surface brightness profile, and we test a new method for studying GC properties. Specifically, we decompose the galaxy light into its spheroid (assumed to represent the bulge + halo components) and disk components and use it to assign to each GC a probability of belonging to one of the two components. Then we model the galaxy kinematics, assuming a disk and spheroidal component, using planetary nebulae (PNe) and integrated stellar light. We use this kinematic model and the probability previously obtained from the photometry to recalculate for each GC its likelihood of being associated with the disk, the spheroid, or neither. We find th...
Stathopoulos, Andreas
2007-01-01
We present a new algorithm that computes eigenvalues and eigenvectors of a Hermitian positive definite matrix while solving a linear system of equations with Conjugate Gradient (CG). The algorithm capitalizes on the vectors already available from CG, building a small window of vectors that approximates the eigenvectors. While this window is restarted in a locally optimal way, the CG is not. Our algorithm converges almost identically to unrestarted Lanczos, yet without the need to store all Lanczos vectors. After the solution of the linear system, eigenvectors that have not accurately converged can be improved in an incremental fashion by solving additional linear systems. When solving systems with multiple right hand sides, eigenvectors identified in earlier linear systems can be used to deflate, and thus accelerate, the convergence of subsequent systems. We have used this algorithm with excellent results in lattice QCD applications, where hundreds of right hand sides may be needed. Specifically, our deflatio...
Adams, Allan; Schaefer, Thomas; Steinberg, Peter; Thomas, John E
2012-01-01
Strongly correlated quantum fluids are phases of matter that are intrinsically quantum mechanical, and that do not have a simple description in terms of weakly interacting quasi-particles. Two systems that have recently attracted a great deal of interest are the quark-gluon plasma, a plasma of strongly interacting quarks and gluons produced in relativistic heavy ion collisions, and ultracold atomic Fermi gases, very dilute clouds of atomic gases confined in optical or magnetic traps. These systems differ by more than 20 orders of magnitude in temperature, but they were shown to exhibit very similar hydrodynamic flow. In particular, both fluids exhibit a robustly low shear viscosity to entropy density ratio which is characteristic of quantum fluids described by holographic duality, a mapping from strongly correlated quantum field theories to weakly curved higher dimensional classical gravity. This review explores the connection between these fields, and it also serves as an introduction to the Focus Issue of N...
We derive commensurate scale relations which relate perturbatively calculable QCD observables to each other, including the annihilation ratio Re+e-, the heavy quark potential, τ decay, and radiative corrections to structure function sum rules. For each such observable one can define an effective charge, such as αR(√s)/π ≡ R e+e-(√s)/(3Σeq2)-1. The commensurate scale relation connecting the effective charges for observables A and B has the form αA(QA) αB(QB)(1 + r A/Bπ/αB + hor-ellipsis), where the coefficient rA/B is independent of the number of flavors ∫ contributing to coupling renormalization, as in BLM scale-fixing. The ratio of scales QA/QB is unique at leading order and guarantees that the observables A and B pass through new quark thresholds at the same physical scale. In higher orders a different renormalization scale Qn* is assigned for each order n in the perturbative series such that the coefficients of the series are identical to that of a invariant theory. The commensurate scale relations and scales satisfy the renormalization group transitivity rule which ensures that predictions in PQCD are independent of the choice of an intermediate renormalization scheme C. In particular, scale-fixed predictions can be made without reference to theoretically constructed singular renormalization schemes such as MS. QCD can thus be tested in a new and precise way by checking that the effective charges of observables track both in their relative normalization and in their commensurate scale dependence. The commensurate scale relations which relate the radiative corrections to the annihilation ratio Re+e- to the radiative corrections for the Bjorken and Gross-Llewellyn Smith sum rules are particularly elegant and interesting
Polyakov loop and the color-flavor locked phase of Quantum Chromodynamics
Ciminale, M; Ruggieri, M; Gatto, R
2007-01-01
We consider the Polyakov Nambu Jona Lasinio model with three massless quarks at high density and moderate temperature in the superconductive color flavor locking phase. We compute the critical temperature $T_c$ as a function of the baryonic chemical potential for the phase transition from the superconductive state to the normal phase. We find that $T_c$ is higher by a factor 1.5 -2 in comparison to the model containing no Polyakov loop. We also compute the specific heat $C_v$ near the second order phase transition and we show that the inclusion of the Polyakov loop does not change the value of the critical exponent.
Developments in lattice quantum chromodynamics for matter at high temperature and density
Gert Aarts
2015-05-01
A brief overview of the QCD phase diagram at nonzero temperature and density is provided. It is explained why standard lattice QCD techniques are not immediately applicable for its determination, due to the sign problem. A selection of recent lattice approaches that attempt to evade the sign problem are then discussed and classified according to the underlying principle: constrained simulations (density of states, histograms), holomorphicity (complex Langevin, Lefschetz thimbles), partial summations (clusters, subsets, bags) and change in integration order (strong coupling, dual formulations).
A model of unified quantum chromodynamics and Yang-Mills gravity
Hsu, Jong-Ping
2011-01-01
Based on a generalized Yang-Mills framework, gravitational and strong interactions can be unified in analogy with the unification in the electroweak theory. By gauging $T(4) \\times [SU(3)]_{color} $ in flat space-time, we have a unified model of chromo-gravity with a new tensor gauge field, which couples universally to all gluons, quarks and anti-quarks. The space-time translational gauge symmetry assures that all wave equations of quarks and gluons reduce to a Hamilton-Jacobi equation with the same `effective Riemann metric tensors' in the geometric-optics (or classical) limit. The emergence of effective metric tensors in the classical limit is essential for the unified model to agree with experiments. The unified model suggests that all gravitational, strong and electroweak interactions appear to be dictated by gauge symmetries in the generalized Yang-Mills framework.
Challenges to quantum chromodynamics: Anomalous spin, heavy quark, and nuclear phenomena
The general structure of QCD meshes remarkably well with the facts of the hadronic world, especially quark-based spectroscopy, current algebra, the approximate point-like structure of large momentum transfer inclusive reactions, and the logarithmic violation of scale invariance in deep inelastic lepton-hadron reactions. QCD has been successful in predicting the features of electron-positron and photon-photon annihilation into hadrons, including the magnitude and scaling of the cross sections, the shape of the photon structure function, the production of hadronic jets with patterns conforming to elementary quark and gluon subprocesses. The experimental measurements appear to be consistent with basic postulates of QCD, that the charge and weak currents within hadrons are carried by fractionally-charged quarks, and that the strength of the interactions between the quarks, and gluons becomes weak at short distances, consistent with asymptotic freedom. Nevertheless in some cases, the predictions of QCD appear to be in dramatic conflict with experiment. The anomalies suggest that the proton itself as a much more complex object than suggested by simple non-relativistic quark models. Recent analyses of the proton distribution amplitude using QCD sum rules points to highly-nontrival proton structure. Solutions to QCD in one-space and one-time dimension suggest that the momentum distributions of non-valence quarks in the hadrons have a non-trival oscillatory structure. The data seems also to be suggesting that the ''intrinsic'' bound state structure of the proton has a non- negligible strange and charm quark content, in addition to the ''extrinsic'' sources of heavy quarks created in the collision itself. 144 refs., 46 figs., 2 tabs
Color transparency and the structure of the proton in quantum chromodynamics
Many anomalies suggest that the proton itself is a much more complex object than suggested by simple non-relativistic quark models. Recent analyses of the proton distribution amplitude using QCD sum rules points to highly-nontrivial proton structure. Solutions to QCD in one-space and one-time dimension suggest that the momentum distributions of non-valence quarks in the hadrons have a non-trivial oscillatory structure. The data seems also to be suggesting that the ''intrinsic'' bound state structure of the proton has a non-negligible strange and charm quark content, in addition to the ''extrinsic'' sources of heavy quarks created in the collision itself. As we shall see in this lecture, the apparent discrepancies with experiment are not so much a failure of QCD, but rather symptoms of the complexity and richness of the theory. An important tool for analyzing this complexity is the light-cone Fock state representation of hadron wavefunctions, which provides a consistent but convenient framework for encoding the features of relativistic many-body systems in quantum field theory. 121 refs., 44 figs., 1 tab
Polyakov loop and the color-flavor locked phase of Quantum Chromodynamics
Ciminale, M.; Nardulli, G.; Ruggieri, M.; Gatto, R.
2007-01-01
We consider the Polyakov Nambu Jona Lasinio model with three massless quarks at high density and moderate temperature in the superconductive color flavor locking phase. We compute the critical temperature $T_c$ as a function of the baryonic chemical potential for the phase transition from the superconductive state to the normal phase. We find that $T_c$ is higher by a factor 1.5 -2 in comparison to the model containing no Polyakov loop. We also compute the specific heat $C_v$ near the second ...
Brodsky, S.J. [Stanford Linear Accelerator Center, Menlo Park, CA (United States); Lu, H.J. [Maryland Univ., College Park, MD (United States). Dept. of Physics
1994-10-01
We derive commensurate scale relations which relate perturbatively calculable QCD observables to each other, including the annihilation ratio R{sub e+}e{sup {minus}}, the heavy quark potential, {tau} decay, and radiative corrections to structure function sum rules. For each such observable one can define an effective charge, such as {alpha}{sub R}({radical}s)/{pi} {equivalent_to} R {sub e+}e{sup {minus}}({radical}s)/(3{Sigma}e{sub q}{sup 2}){minus}1. The commensurate scale relation connecting the effective charges for observables A and B has the form {alpha}{sub A}(Q{sub A}) {alpha}{sub B}(Q{sub B})(1 + r {sub A/B}{sub {pi}}/{sup {alpha}B} + {hor_ellipsis}), where the coefficient r{sub A/B} is independent of the number of flavors {integral} contributing to coupling renormalization, as in BLM scale-fixing. The ratio of scales Q{sub A}/Q{sub B} is unique at leading order and guarantees that the observables A and B pass through new quark thresholds at the same physical scale. In higher orders a different renormalization scale Q{sup n*} is assigned for each order n in the perturbative series such that the coefficients of the series are identical to that of a invariant theory. The commensurate scale relations and scales satisfy the renormalization group transitivity rule which ensures that predictions in PQCD are independent of the choice of an intermediate renormalization scheme C. In particular, scale-fixed predictions can be made without reference to theoretically constructed singular renormalization schemes such as MS. QCD can thus be tested in a new and precise way by checking that the effective charges of observables track both in their relative normalization and in their commensurate scale dependence. The commensurate scale relations which relate the radiative corrections to the annihilation ratio R{sub e{sup +}e{sup {minus}}} to the radiative corrections for the Bjorken and Gross-Llewellyn Smith sum rules are particularly elegant and interesting.
A model for deep inelastic lepton-hadron scattering is presented that includes non-perturbative effects as intrinsic transverse momentum, target, quark masses and hadronization, in QCD-perturbation theory in a way consistent with factorization. It allows realistic predictions for the Q2-evolution of structure functions as well as in combination with a semi-classical fragmentation model using a Monte-Carlo simulation for any measurable quantity in deep-inelastic scattering. The model is applied to various observables in muon-proton-reactions. The numerical results which are in good agreement with experimental data for a mean intrinsic transverse momentum of =0.7 GeV, differ from those of pure perturbation theory. (orig.)
The road towards the international linear collider: Higgs, top/quantum chromodynamics, loops
S Heinemeyer
2007-11-01
The international linear +− collider (ILC) could go into operation in the second half of the upcoming decade. Experimental analyses and theory calculations for the physics at the ILC are currently performed. We review recent progress, as presented at the LCWS06 in Bangalore, India, in the fields of Higgs boson physics and top/QCD. Also the area of loop calculations, necessary to achieve the required theory precision, is included.
Two-dimensional sigma models: modelling non-perturbative effects of quantum chromodynamics
The basic features of the O(N) sigma models are discussed. Some aspects of the Wilson opera,tor expansion (OPE) are considered: mathematical formulation of OPE, its physical meaning and non-perturbative vacuum expectations of local operators. It is concluded that OPE is well defined outside the perturabation theory. The anomaly in the trace of the energy-momentum tensor is studied. It is shown that the anomaly determines the masses of physical particles. Low-energy theorems which relate low-energy scattering amplitudes to non-perturbative vacuum expectation values of some operators are investigated
A survey of lattice results on ﬁnite temperature quantum chromodynamics
E Laermann
2003-04-01
The talk summarizes some new results of lattice investigations of QCD at ﬁnite temperature. The topics discussed cover the ﬂavor dependence of the critical temperature and the equation-of-state as well as hadronic correlation functions.
Experimental results on QCD [Quantum Chromodynamics] from e+e- annihilation
A review is given on QCD results from studying e+e- annihilation with the PEP and PETRA storage rings with special emphasis on jet physics and the determination of the strong coupling constant α/sub s/. 92 refs., 28 figs., 3 tabs
Experimental results on QCD (Quantum Chromodynamics) from e/sup +/e/sup -/ annihilation
de Boer, W.
1987-09-01
A review is given on QCD results from studying e/sup +/e/sup -/ annihilation with the PEP and PETRA storage rings with special emphasis on jet physics and the determination of the strong coupling constant ..cap alpha../sub s/. 92 refs., 28 figs., 3 tabs.
As the value of the longitudinal momentum carried by partons in a ultra-relativistic hadron becomes small, one observes a growth of their density. When the parton density becomes close to a value of order 1/αs, it does not grow any longer, it saturates. These high density effects seem to be well described by the Color Glass Condensate effective field theory. On the experimental side, the LHC provides the best tool ever for reaching the saturated phase of hadronic matter. For this reason saturation physics is a very active branch of QCD during these past and coming years since saturation theories and experimental data can be compared. I first deal with the phenomenology of the proton-lead collisions performed in winter 2013 at the LHC and whose data are about to be available. I compute the di-gluon production cross-section which provides the simplest observable for funding quantitative evidences of saturation in the kinematic range of the LHC. I also discuss the limit of the strongly correlated final state at large transverse momenta and by the way, generalize parton distribution to dense regime. The second main topic is the quantum evolution of the quark and gluon spectra in nucleus-nucleus collisions having in mind the proof of its universal character. This result is already known for gluons and here I detail the calculation carefully. For quarks universality has not been proved yet but I derive an intermediate leading order to next-to leading order recursion relation which is a crucial step for extracting the quantum evolution. Finally I briefly present an independent work in group theory. I detail a method I used for computing traces involving an arbitrary number of group generators, a situation often encountered in QCD calculations. (author)
A model of unified quantum chromodynamics and Yang-Mills gravity
HSU Jong-Ping
2012-01-01
Based on a generalized Yang-Mills framework,gravitational and strong interactions can be unified in analogy with the unification in the clectroweak theory.By gauging T(4) × [SU(3)]color in fiat space-time,we have a unified model of chromo-gravity with a new tensor gauge field,which couples universally to all gluons,quarks and anti-quarks.The space-time translational gauge symmetry assures that all wave equations of quarks and gluons reduce to a Hamilton-Jacobi equation with the same ‘effective Riemann metric tensors' in the geometric-optics (or classical) limit.The emergence of effective metric tensors in the classical limit is essential for the unified model to agree with experiments.The unified model suggests that all gravitational,strong and electroweak interactions appear to be dictated by gauge symmetries in the generalized Yang-Mills framework.
The MIT bag model Hamiltonian as an effective Hamiltonian of quantum chromodynamics
A possibility of derivation of the MIT bag model Hamiltonian from QCD is discussed. The bags are interpreted as wave packets of hadrons localized in the region x ≤ R where R is the bag radius. In the Fock space of gluodynamics a subspace P of the localized states is constructed and it is shown that projection of the Yang-Mills Hamiltonian into P has a representation in the Fock space PV of a Hamiltonian HV that depends on gluon fields defined inside a spherical cavity of radius R. The gluon fields obey boundary conditions. The one-to-one correspondence of vectors P and PV conserves Hermitian product, matrix elements of the Yang-Mills Hamiltonian between the states P are equal to the matrix elements of HV between the corresponding states of PV. Explicit form of the Hamiltonian HV is found. The MIT bag model Hamiltonian approximates in rough features the Hamiltonian HV
19th High-Energy Physics International Conference in Quantum Chromodynamics (QCD)
2016-01-01
Experimental and Theoretical Issues on: Perturbative and Non-Perturbative QCD QCD at colliders Tau, Kaon and B decays, CP-violation Exotic Hadrons Spectroscopy Precision Tests of the Standard Model Physics Beyond the Standard Model.
Quantum chromodynamics phase transition in the early Universe and quark nuggets
Abhijit Bhattacharyya; Shibaji Banerjee; Sanjay K Ghosh; Sibaji Raha; Bikash Sinha; Hiroshi Toki
2003-05-01
A ﬁrst-order quark hadron phase transition in the early Universe may lead to the formation of quark nuggets. The baryon number distribution of these quark nuggets have been calculated and it has been found that there are sizeable number of quark nuggets in the stable sector. The nuggets can clump and form bigger objects in the mass range of 0.0003$M_{\\odot}$ to 0.12$M_{\\odot}$. It has been discussed that these bigger objects can be possible candidates for cold dark matter.
During the first year of our renewed research program significant progress has been made on the following research problems: in computing both elastic and inelastic pion-nucleon scattering phase shifts in the (1,1) and (3,3) channels within our pionic nontopological soliton model; in developing a new method for computing quantum soliton states and energies for all momenta in relativistic quantum field theory; and in applying the subsidiary condition theorem to soliton quantization in relativistic quantum field theory. These topics are discussed in this paper
Spin Effects in Quantum Chromodynamics and Recurrence Lattices with Multi-Site Exchanges
Ananikyan, Lev
2009-01-01
In this thesis, we consider some spin effects in QCD and recurrence lattices with multi-site exchanges. Main topic of our manuscript are critical phenomena in spin systems defined on the recurrence lattices. Main tool of our approach is the method of recursive (hierarchical) lattices. We apply the method of dynamical mapping (or recursive lattices) for investigation of magnetic properties of the fluid and solid $^3$He, phase transitions in crystals and macromolecules. First, we analyze the helix-coil phase transition for polypeptides and proteins, and describe an quasi unfolding transition (like the cold denaturation process) for the degree of helicity (the order parameter for macromolecules). Next we consider the recurrent models of $^3$He defined on the square, Husimi and hexagon lattices. Using the method of dynamical mapping, the magnetization curves with plateaus, bifurcation point and one period doubling are obtained. Then we investigate the model with cubic symmetry defined on the Bethe lattice and con...
Low-energy effective models for two-flavor quantum chromodynamics and the universality hypothesis
Our thesis is centered around the question of which order the chiral phase transition of two-flavor QCD is. First of all we outline several general aspects of phase transitions which are of central importance for the understanding of the RG approach towards them. Our focus lies on reviewing the universality hypothesis, a crucial ingredient when it comes to the construction of effective theories for order parameters, the credibility of which often heavily depends on universality arguments. We finish the chapter with an attempt to formulate the latter more precisely than usually done. The next chapter discusses the chiral phase transition from a general point of view. We supplement well-known facts with a detailed discussion of the so-called O(4) conjecture. Thereafter we introduce the nonperturbative method we use, the FRG method. Furthermore, we discuss the relation between effective models for QCD and the underlying fundamental theory making use of the FRG perspective. The next chapter is concerned with a mathematical subject indispensable for our approach towards the study of phase transitions, namely the systematic construction of polynomial invariants characterizing a given symmetry. With this thesis we point out its relevance in the context of high-energy physics. We present a simple, but novel, brute-force algorithm to effectively construct invariants of a given polynomial order. The next chapter is devoted to RG studies of several dimensionally reduced theories which are capable to either predict or to rule out the possible existence of a second-order phase transition. Of main interest for us is the linear sigma model, particularly in presence of the axial anomaly. It turns out that the fixed-point structure of the latter is rather complicated, requiring a deeper understanding of the underlying method and its preconditions. This leads us to a careful analysis of the fixed-point structure of several models, which is of great benefit for our review of the universality hypothesis and has several spin-off effects. For example, in the course of studying the influence of vector and axial-vector mesons we encounter a new universality class, which might be more relevant in other areas where chirality plays a role. Some important questions, however, cannot be addressed in the framework of dimensionally reduced theories where the explicit dependence of temperature has been eliminated. We are therefore pushed towards FRG studies where the temperature is kept as an explicit variable. We note that a great part of our work consisted in finding our own implementations of suitable algorithms to solve the encountered partial differential equations numerically. Then our main goal, the application to effective models for QCD, is discussed.
A model of unified quantum chromodynamics and Yang-Mills gravity
Hsu, Jong-Ping
2011-01-01
Based on a generalized Yang-Mills framework, gravitational and strong interactions can be unified in analogy with the unification in the electroweak theory. By gauging $T(4) \\times [SU(3)]_{color} $ in flat space-time, we have a unified model of chromo-gravity with a new tensor gauge field, which couples universally to all gluons, quarks and anti-quarks. The space-time translational gauge symmetry assures that all wave equations of quarks and gluons reduce to a Hamilton-Jacobi equation with t...
应和平; 董绍静; 张剑波
2003-01-01
With an exact chiral symmetry, overlap fermions allow us to reach very light quark region. In the minimummps = 179 MeV, the quenched chiral logarithm diverge is examined. The chiral logarithm parameter δ is calculatedfrom both the pseudo-scalar meson mass mp2s diverge channel and the pseudo-scalar decay constant f p channel.In both the cases, we obtain δ = 0.25 ± 0.03. We also observe that the quenchedchiral logarithm diverge occursonly in the mps ≤400 MeV region.
Mueller, B.
1993-05-15
This report discusses research in the following topics: Hadron structure physics; relativistic heavy ion collisions; finite- temperature QCD; real-time lattice gauge theory; and studies in quantum field theory.
Renormalization scheme-dependence of perturbative quantum chromodynamics corrections to quarkonia
QCD radiative corrections to physical quantities are studied using Stevenson's principle of minimal sensitivity (PMS) to define the renormalization. We examine several naive potentials (Cornell group, power law and logarithmic), as well as the more sophisticated Richardson model in order to determine the spectra for the non-relativistic heavy charmonium and bottomonium systems. Predictions are made for the values of hyperfine splittings, leptonic and hadronic decay widths and E1 transition rates for these families of mesons. It is shown that good agreement with experimental data may be achieved by using a constant value of Λ/sub QCD/, which is determined by the PMS scheme and the potential model
Bhaskar Jyoti Hazarika; D K Choudhury
2010-09-01
We used variationally improved perturbation theory (VIPT) in calculating the slope and curvature of Isgur–Wise (I–W) function with the Cornell potential $− \\dfrac{4_{s}}{3r} br + c$ instead of the usual stationary state perturbation theory as done earlier. We used $−(4_{s} /3r)$, i.e. the Coulombic potential, as the parent and the linear one, i.e. $br +c$ as the perturbed potential in the theory and calculated the slope and curvature of Isgur–Wise function including three states in the summation involved in the first-order correction to wave function in the method.
A brief summary of the progress made for the year is given for each of the following areas: (1) quark-gluon plasma and relativistic heavy ion collisions (nine contributions); (2) effective theories for hadrons and nuclei (four contributions); (4) renormalization group approach to field theory at finite temperature; (5) symmetry-preserving regularization; and (6) an effective field theory approach to the cosmological constant problem
XIONG Wen-Yuan; HU Zhao-Hui; WANG Xin-Wen; ZHOU Li-Juan; XIA Li-Xin; MA Wei-Xing
2008-01-01
Based on analysis of scattering matrix S, and its properties such as analyticity, unitarity, Lorentz invariance, and crossing symmetry relation, the Regge theory was proposed to describe hadron-hadron scattering at high energies before the advent of QCD, and correspondingly a Reggeon concept was born as a mediator of strongly interaction. This theory serves as a successful approach and has explained a great number of experimental data successfully, which proves that the Regge theory can be regarded as a basic theory of hadron interaction at high energies and its validity in many applications. However, as new experimental data come out, we have some difficulties in explaining the data. The new experimental total cross section violates the predictions of Regge theory, which shows that Regge formalism is limited in its applications to high energy data. To understand new experimental measurements, a new exchange theory was consequently born and its mediator is called Pomeron, which has vacuum quantum numbers. The new theory named as Pomeron exchange theory which reproduces the new experimental data of diffractive processes successfully. There are two exchange mediators: Reggeon and Pomeron. Reggeon exchange theory can only produce data at the relatively lower energy region, while Pomeron exchange theory fits the data only at higher-energy region, separately. In order to explain the data in the whole energy region, we propose a Reggeon-Pomeron model to describe high-energy hadron-hadron scattering and other diffractive processes. Although the Reggeon-Pomeron model is successful in describing high-energy hadron-hadron interaction in the whole energy region, it is a phenomenological model After the advent of QCD, people try to reveal the mystery of the phenomenological theory from QCD since hadron-hadron processes is a strong interaction, which is believed to be described by QCD. According to this point of view, we study the QCD nature of Reggeon and Pomeron. We claim that the Reggeon exchange is an exchange of multigluon, the color singlet gluon bound state. In particular, the Pomeron could be a Reggeized tensor glueba11 ξ(2230) with mass of 2.23 GeV, quantum numbers IG, JPC = 0+, 2++ and decay width of about 100 MeV. The glueball exchange theory reproduces data quite well. Accordingly, we believe that the Odderon, consisting of three Reggeized gluons, and predicted by QCD, should also contribute to hadron-hadron scattering and many other diffractive processes. We search for the Odderon by studying pp and pp elastic scatterings at high energies. Our investigations on the differential cross section da / dt of hadron-hadron scattering at various energies and comparisons with experimental data show that the Odderon plays an essential role in fitting to data. Therefore, we suggest that the measurements should be urgently done in order to confirm the existences of the Odderon and to test QCD.
This report briefly discusses the following topics: quark-gluon plasma and high-energy collisions; hadron structure and chiral dynamics; nonperturbative studies and nonabelian gauge theories; and studies in quantum field theory
The form factors which govern the semileptonic decays of pseudoscalar particles (M→M'+l+ν(l)) are constrained by the knowledge of the two-point function PIsup(μv)(q) in the deep euclidean region. We derive the precise constrains from a QCD calculation of PIsup(μv) which includes perturbative contributions to two-loops as well as leading non-perturbative contributions. Applications to PIl3, Kl3 and D+→antiK0 e+νe decays are discussed
A study on the determination of the scale parameter ΛMS of quantum chromodynamics at LEP I energies
A method of measuring independently of jet rates the scale parameter Λsub(anti Manti S) for the determination of the running coupling constant αs of QCD is investigated. Using the LUND-program with exact matrix elements, the method is based on the energy dependence of observables like reduced thrust, jet masses and integrated asymmetry of energy-energy correlation (IAEEC). Only the IAEEC is able to reproduce the input scale parameter, Λsub(anti Manti S)=0.500 GeV, whereas the other variables yield smaller results than predicted. If the three jet cross section is, however, formulated with ERT-matrix elements, which are not included in the standard LUND code, it is possible to reproduce Λsub(anti Manti S) also from reduced thrust and jet masses. (orig.)
We have constructed fundamental tests which can be used to probe discrete symmetries, and their possible violations, in the required ''new physics'' beyond the standard model. For spin 0 decay into tau+tau- yielding an observable lepton pair l2l2 we have obtained analytically the full sequential decay correlation function I(E1, E2, cos psi12) = S + γ/sub CP/D in the Higgstechnipion rest frame. For fixed psi12, contour plots of this E1 energy-E2 energy correlation function have been made for M/sub H/ = 9 GeV and 70 GeV to show the difference between γ/sub CP/ = +-. We are continuing to investigate our proposal that partons be identified with nearly degenerate, coherent quark-gluon ''jet'' states in order to settle whether the associated ''jet based factorization'' is a natural property of QCD and whether it maintains the universality of mass singularities and the factorization of QCD processes into short-distance and long-distance parts. 4 figs
Inclusive measurements of protons and antiprotons, at ninety degrees, generated in proton-antiproton or proton-proton interactions, give different information. After an improvement in the particles' identification as a result of the association of silicagel detectors and the time of flight, the following results were achieved: the global test of the CR and CP invariances in strong proton-antiproton, and the need of a proton scalar diquark under-structure to explain the anomalous level of protons, either in agreement to other similar experiments or very different. The name of covalon or coquark for this bound state is proposed. In ultra-relativistic heavy ions interactions, the covalons' suppression would be a new and strong identification sign for quarks and gluons plasma
Hisao Nakkagawa; Hiroshi Yokota; Koji Yoshida; Yuko Fueki
2003-05-01
Chiral phase transition in thermal QCD is studied by using the Dyson–Schwinger (DS) equation in the real time hard thermal loop approximation. Our results on the critical temperature and the critical coupling are signiﬁcantly different from those in the preceding analyses in the ladder DS equation, showing the importance of properly taking into account the essential thermal effects, namely the Landau damping and the unstable nature of thermal quasiparticles.
The present state of the art in elementary particle theory is reviewed. Topics include quantum electrodynamics, weak interactions, electroweak unification, quantum chromodynamics, and grand unified theories. 113 references
(Experimental and theoretical basic research in high energy physics)
1991-04-01
This report discusses the measurement of charm and b decays via hadronic production in a hybrid emulsion spectrometer, quantum chromodynamics, quantum electrodynamics, weak interactions, and cosmological applications. (LSP)
[Experimental and theoretical basic research in high energy physics
This report discusses the measurement of charm and b decays via hadronic production in a hybrid emulsion spectrometer, quantum chromodynamics, quantum electrodynamics, weak interactions, and cosmological applications
Expectations for ultra-high energy interactions
Strong interactions at ultra-high energies are discussed with emphasis on the hadrons produced in high energy collisions. Evidence is considered that quantum chromodynamics might be the right theory, and also some estimates are given of quantum chromodynamics asymptotic-freedom phenomena, the work under discussion being very preliminary. 6 references
Quarks in Coulomb gauge perturbation theory
Popovici, C; Reinhardt, H
2008-01-01
Coulomb gauge quantum chromodynamics within the first order functional formalism is considered. The quark contributions to the Dyson-Schwinger equations are derived and one-loop perturbative results for the two-point functions are presented.
Glossary for new particles and new quantum numbers
Definitions of the terms; asymptotic freedom, charm, charmonium, colour, gauge theories, gluon, hadron, heavy lepton, lepton, quantum chromodynamics (q.c.d.), quark, quark confinement, unified gauge theory, weak interactions, and W-meson, are given. (U.K.)
Research in high energy physics
This report discusses research being conducted in high energy physics in the following areas: quantum chromodynamics; drift chambers; proton-antiproton interactions; particle decays; particle production; polarimeters; quark-gluon plasma; and conformal field theory. (LSP)
Spectroscopy of mesonic states containing light quarks (u,d,s) or gluons
In this thesis the description of meson spectra in the framework of quantum chromodynamics is reviewed. Particularly considered are quarkonium states, glueballs, hermaphrodites, and four-quark states. (HSI)
Nuclear theory progress report, April 1991--April 1992
1992-07-01
This report discusses research in nuclear theory on the following topics: nuclear astrophysics; quantum chromodynamics; quark matter; symmetry breaking; heavy ion reactions; hadronic form factors; neutrino processes; nuclear structure; weak interaction physics; and other related topics. (LSP)
Nuclear theory progress report, April 1991--April 1992
1992-01-01
This report discusses research in nuclear theory on the following topics: nuclear astrophysics; quantum chromodynamics; quark matter; symmetry breaking; heavy ion reactions; hadronic form factors; neutrino processes; nuclear structure; weak interaction physics; and other related topics. (LSP)
Cross sections for five jet production above the W+W- threshold in e+e- annihilation
We describe the calculation of five jet production from the W+W- intermediate state in e+e- annihilation in lowest order quantum chromodynamics. Some results for integrated Cross-sections are presented. (author)
Intriguing solutions of the Bethe-Salpeter equation for radially excited pseudoscalar charmonia
Šauli, Vladimír
2014-01-01
Roč. 90, č. 1 (2014), 016005. ISSN 1550-7998 Institutional support: RVO:61389005 Keywords : quantum chromodynamics * confinement * quarks * gluons Subject RIV: BE - Theoretical Physics Impact factor: 4.643, year: 2014
EMC effect: asymptotic freedom with nuclear targets
General features of the EMC effect are discussed within the framework of quantum chromodynamics as expressed via the operator product expansion and asymptotic freedom. These techniques are reviewed with emphasis on the target dependence. 22 references
Phase diagram of two-color quark matter at nonzero baryon and isospin density
Andersen, J. O.; Brauner, Tomáš
2010-01-01
Roč. 81, č. 9 (2010), 096004/1-096004/14. ISSN 0556-2821 Institutional research plan: CEZ:AV0Z10480505 Keywords : COLOR SUPERCONDUCTIVITY * QUANTUM CHROMODYNAMICS * PERTURBATION-THEORY Subject RIV: BE - Theoretical Physics
Theory and phenomenology of strong and weak interaction high energy physics
This paper reviews research done on theoretical high energy physics. Areas of discussion are: chiral symmetry; quantum chromodynamics; quark-gluon plasma; particle decay of kaons; photonuclear reactions from cosmic ray showers; symmetry breaking and other related topics
Fritzsch, Harald; Heusch, Karin
Introduction -- Electrons and atomic nuclei -- Quantum properties of atoms and particles -- The knives of Democritus -- Quarks inside atomic nuclei -- Quantum electrodynamics -- Quantum chromodynamics -- Mesons, baryons, and quarks -- Electroweak interactions -- Grand unification -- Conclusion.
Research in high energy physics
This report discusses research being conducted in high energy physics in the following areas: quantum chromodynamics; drift chambers; proton-antiproton interactions; particle decays; particle production; polarimeters; quark-gluon plasma; and conformed field theory
Parton production via vacuum polarization
We discuss the production mechanism of partons via vacuum polarization during the very early, gluon-dominated phase of an ultrarelativistic heavy-ion collision in the framework of the background field method of quantum chromodynamics. (author)
Problems of high energy physics
Some problems of high energy physics are discussed. The main attention is paid to describibg the standard model. The model comprises quantum chromodynamics and electroweak interaction theory. The problem of CP breaking is considered as well. 8 refs.; 1 tab
Research in high energy physics
This report discusses research being conducted in high energy physics in the following areas; quantum chromodynamics; drift chambers; proton-antiproton interactions; particle decays; particle production; polarimeters; quark-gluon plasma; and conformed field theory
2013 CERN - Latin-American School of High-Energy Physics
Mulders, M; CLASHEP 2013
2015-01-01
The CERN–Latin-American School of High-Energy Physics is intended to give young physicists an introduction to the theoretical aspects of recent advances in elementary particle physics. These proceedings contain lecture notes on the Standard Model of electroweak interactions, quantum chromodynamics, flavour physics, quantum chromodynamics under extreme conditions, cosmic-ray physics, cosmology, recent highlights of LHC results, practical statistics for particle physicists and a short introduction to the principles of particle physics instrumentation.
An empirical approach to the theory of particle and nuclear phenomena: Review and some new ideas
Raja Ramanna; Sudhir R Jain
2001-08-01
Experimental data on masses and lifetimes of unstable particles falls into a pattern, a brief review of some interesting consequences is presented here. From the experience in semiclassical methods and recent advances in quantum chromodynamics, it is proposed that an appropriate generalization of the Gutzwiller trace formula for ﬁeld theories may lead to a systematic semiclassical chromodynamics theory. The theory can be developed to get appropriate dynamics leading to an explanation of pattern discovered in the empirical data.