The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
B R Webber - One of the best experts on this subject based on the ideXlab platform.
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herwig 6 an event generator for hadron emission reactions with interfering gluons including supersymmetric processes
Journal of High Energy Physics, 2001Co-Authors: Gennaro Corcella, G Marchesini, I G Knowles, M H Seymour, Stefano Moretti, Kosuke Odagiri, Peter J Richardson, B R WebberAbstract:HERWIG is a general-purpose Monte Carlo event generator, which includes the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron scattering and soft hadron-hadron collisions in one package. It uses the parton-shower approach for initial- and final-state QCD radiation, including colour coherence effects and azimuthal correlations both within and between jets. This article updates the description of HERWIG published in 1992, emphasising the new features incorporated since then. These include, in particular, the matching of first-order matrix elements with parton showers, a more correct treatment of heavy quark decays, and a wide range of new processes, including many predicted by the Minimal Supersymmetric Standard Model, with the option of R-parity violation. At the same time we offer a brief review of the physics underlying HERWIG, together with details of the input and control parameters and the output data, to provide a self-contained guide for prospective users of the program.
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herwig 6 5 an event generator for hadron emission reactions with interfering gluons including supersymmetric processes
arXiv: High Energy Physics - Phenomenology, 2000Co-Authors: Gennaro Corcella, G Marchesini, I G Knowles, M H Seymour, Stefano Moretti, Kosuke Odagiri, Peter J Richardson, B R WebberAbstract:HERWIG is a general-purpose Monte Carlo event generator, which includes the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron scattering and soft hadron-hadron collisions in one package. It uses the parton-shower approach for initial- and final-state QCD radiation, including colour coherence effects and azimuthal correlations both within and between jets. This article updates the description of HERWIG published in 1992, emphasising the new features incorporated since then. These include, in particular, the matching of first-order matrix elements with parton showers, a more correct treatment of heavy quark decays, and a wide range of new processes, including many predicted by the Minimal Supersymmetric Standard Model, with the option of R-parity violation. At the same time we offer a brief review of the physics underlying HERWIG together with details of the input and control parameters and the output data, to provide a self-contained guide for prospective users of the program. This version of the manual (version 3) is updated to HERWIG version 6.5, which is expected to be the last major release of Fortran HERWIG. Future developments will be implemented in a new C++ event generator, HERWIG++.
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longitudinally invariant k clustering algorithms for hadron hadron collisions
Nuclear Physics, 1993Co-Authors: S Catani, M H Seymour, Yu L Dokshitzer, B R WebberAbstract:Abstract We propose a version of the QCD-motivated “k⊥” jet-clustering algorithm for hadron-hadron collisions which is invariant under boosts along the beam directions. This leads to improved factorization properties and closer correspondence to experimental practice at hadron colliders. We examine alternative definitions of the resolution variables and cluster recombination scheme, and show that the algorithm can be implemented efficiently on a computer to provide a full clustering history of each event. Using simulated data at √S = 1.8 TeV, we study the effects of calorimeter segmentation, hadronization and the soft underlying event, and compare the results with those obtained using a conventional cone-type algorithm.
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the k clustering algorithm for jets in deep inelastic scattering and hadron collisions
Physics Letters B, 1992Co-Authors: S Catani, Yu L Dokshitzer, B R WebberAbstract:Abstract We propose a new QCD-motivated clustering algorithm to define jets in lepton-hadron and hadron-hadron collisions. It combines the k ⊥ algorithm, proposed earlier for e + e − annihilation, with a pre-clustering procedure that ensures the universal factorization of initial-state collinear singularities.
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herwig 5 1 a monte carlo event generator for simulating hadron emission reactions with interfering gluons
Computer Physics Communications, 1992Co-Authors: G Marchesini, B R Webber, G Abbiendi, I G Knowles, M H Seymour, L StancoAbstract:Abstract HERWIG is a general-purpose particle-physics event generator, which includes the simulation of hard lepton-lepton, lepton-hadron and hadron-hadron scattering and soft hadron-hadron collisions in one package. It uses the parton-shower approach for initial-state and final-state QCD radiation, including colour coherence effects and azimuthal correlations both within and between jets. This article includes a brief review of the physics underlying HERWIG, followed by a description of the program itself. This includes details of the input and control parameters used by the program, and the output data provided by it. Sample output from a typical simulation is given and annotated.
Abdel Nasser Tawfik - One of the best experts on this subject based on the ideXlab platform.
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hadron resonance mass spectrum and lattice qcd thermodynamics
European Physical Journal C, 2003Co-Authors: Frithjof Karsch, K Redlich, Abdel Nasser TawfikAbstract:We confront lattice QCD results on the transition from the hadronic phase to the quark-gluon plasma with hadron resonance gas and percolation models. We argue that for $T\leq T_{\mathrm{c}}$ the equation of state derived from Monte Carlo simulations of (2+1) quark-flavor QCD can be well described by a hadron resonance gas. We examine the quark mass dependence of the hadron spectrum on the lattice and discuss its description in terms of the MIT bag model. This is used to formulate a resonance gas model for arbitrary quark masses which can be compared to lattice calculations. We finally apply this model to the analysis of the quark mass dependence of the critical temperature obtained in lattice calculations. We show that the value of $T_{\mathrm{c}}$ for different quark masses agrees with lines of constant energy density in a hadron resonance gas. For large quark masses a corresponding contribution from a glueball resonance gas is required.
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hadron resonance mass spectrum and lattice qcd thermodynamics
arXiv: High Energy Physics - Phenomenology, 2003Co-Authors: Frithjof Karsch, K Redlich, Abdel Nasser TawfikAbstract:We confront lattice QCD results on the transition from the hadronic phase to the quark--gluon plasma with hadron resonance gas and percolation models. We argue that for T < T_c the equation of state derived from Monte--Carlo simulations of (2+1) quark--flavor QCD can be well described by a hadron resonance gas. We examine the quark mass dependence of the hadron spectrum on the lattice and discuss its description in terms of the MIT bag model. This is used to formulate a resonance gas model for arbitrary quark masses which can be compared to lattice calculations. We finally apply this model to analyze the quark mass dependence of the critical temperature obtained in lattice calculations. We show that the value of T_c for different quark masses agrees with lines of constant energy density in a hadron resonance gas. For large quark masses a corresponding contribution from a glueball resonance gas is required.
K Redlich - One of the best experts on this subject based on the ideXlab platform.
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hadron resonance mass spectrum and lattice qcd thermodynamics
European Physical Journal C, 2003Co-Authors: Frithjof Karsch, K Redlich, Abdel Nasser TawfikAbstract:We confront lattice QCD results on the transition from the hadronic phase to the quark-gluon plasma with hadron resonance gas and percolation models. We argue that for $T\leq T_{\mathrm{c}}$ the equation of state derived from Monte Carlo simulations of (2+1) quark-flavor QCD can be well described by a hadron resonance gas. We examine the quark mass dependence of the hadron spectrum on the lattice and discuss its description in terms of the MIT bag model. This is used to formulate a resonance gas model for arbitrary quark masses which can be compared to lattice calculations. We finally apply this model to the analysis of the quark mass dependence of the critical temperature obtained in lattice calculations. We show that the value of $T_{\mathrm{c}}$ for different quark masses agrees with lines of constant energy density in a hadron resonance gas. For large quark masses a corresponding contribution from a glueball resonance gas is required.
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hadron resonance mass spectrum and lattice qcd thermodynamics
arXiv: High Energy Physics - Phenomenology, 2003Co-Authors: Frithjof Karsch, K Redlich, Abdel Nasser TawfikAbstract:We confront lattice QCD results on the transition from the hadronic phase to the quark--gluon plasma with hadron resonance gas and percolation models. We argue that for T < T_c the equation of state derived from Monte--Carlo simulations of (2+1) quark--flavor QCD can be well described by a hadron resonance gas. We examine the quark mass dependence of the hadron spectrum on the lattice and discuss its description in terms of the MIT bag model. This is used to formulate a resonance gas model for arbitrary quark masses which can be compared to lattice calculations. We finally apply this model to analyze the quark mass dependence of the critical temperature obtained in lattice calculations. We show that the value of T_c for different quark masses agrees with lines of constant energy density in a hadron resonance gas. For large quark masses a corresponding contribution from a glueball resonance gas is required.
V Anosov - One of the best experts on this subject based on the ideXlab platform.
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azimuthal asymmetries of charged hadrons produced in high energy muon scattering off longitudinally polarised deuterons
arXiv: High Energy Physics - Experiment, 2016Co-Authors: C Adolph, M Aghasyan, R Akhunzyanov, M Alexeev, G D Alexeev, A Amoroso, V Andrieux, N V Anfimov, V Anosov, K AugstenAbstract:Single hadron azimuthal asymmetries of positive and negative hadrons produced in muon semi-inclusive deep inelastic scattering off longitudinally polarised deuterons are determined using the 2006 COMPASS data and also combined all deuteron COMPASS data. For each hadron charge, the dependence of the azimuthal asymmetry on the hadron azimuthal angle $\phi$ is obtained by means of a five-parameter fitting function that besides a $\phi$-independent term includes four modulations predicted by theory: $\sin\phi$, $\sin 2 \phi$, $\sin 3\phi$ and $\cos\phi$. The amplitudes of the five terms have been extracted, first, for the hadrons in the whole available kinematic region. In further fits, performed for hadrons from a restricted kinematic region, the $\phi$-dependence is determined as a function of one of three variables (Bjorken-$x$, fractional energy of virtual photon taken by the outgoing hadron and hadron transverse momentum), while disregarding the others. Except the $\phi$-independent term, all the modulation amplitudes are very small, and no clear kinematic dependence could be observed within experimental uncertainties.
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The COMPASS setup for physics with hadron beams
Nuclear Instruments and Methods in Physics Research Section A: Accelerators Spectrometers Detectors and Associated Equipment, 2015Co-Authors: P. Abbon, C Adolph, R Akhunzyanov, G D Alexeev, A Amoroso, V Andrieux, V Anosov, Yu. Alexandrov, M.g. Alexeev, A. AustregesiloAbstract:The main characteristics of the COMPASS experimental setup for physics with hadron beams are described. This setup was designed to perform exclusive measurements of processes with several charged and/or neutral particles in the final state. Making use of a large part of the apparatus that was previously built for spin structure studies with a muon beam, it also features a new target system as well as new or upgraded detectors. The hadron setup is able to operate at the high incident hadron flux available at CERN. It is characterised by large angular and momentum coverages, large and nearly flat acceptances, and good two and three-particle mass resolutions. In 2008 and 2009 it was successfully used with positive and negative hadron beams and with liquid hydrogen and solid nuclear targets. This paper describes the new and upgraded detectors and auxiliary equipment, outlines the reconstruction procedures used, and summarises the general performance of the setup.
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azimuthal asymmetries of charged hadrons produced by high energy muons scattered off longitudinally polarised deuterons
European Physical Journal C, 2010Co-Authors: C Adolph, M Aghasyan, R Akhunzyanov, M Alexeev, G D Alexeev, A Amoroso, V Andrieux, N V Anfimov, V AnosovAbstract:Azimuthal asymmetries in semi-inclusive production of positive (h+) and negative hadrons (h−) have been measured by scattering 160 GeV muons off longitudinally polarised deuterons at CERN. The asymmetries were decomposed in several terms according to their expected modulation in the azimuthal angle φ of the outgoing hadron. Each term receives contributions from one or several spin and transverse-momentum-dependent parton distribution and fragmentation functions. The amplitudes of all φ-modulation terms of the hadron asymmetries integrated over the kinematic variables are found to be consistent with zero within statistical errors, while the constant terms are nonzero and equal for h+ and h− within the statistical errors. The dependencies of the φ-modulated terms versus the Bjorken momentum fraction x, the hadron fractional momentum z, and the hadron transverse momentum \(p_{h}^{T}\) were studied. The x dependence of the constant terms for both positive and negative hadrons is in agreement with the longitudinal double-spin hadron asymmetries, measured in semi-inclusive deep-inelastic scattering. The x dependence of the sin φ-modulation term is less pronounced than that in the corresponding HERMES data. All other dependencies of the φ-modulation amplitudes are consistent with zero within the statistical errors.
Johann Rafelski - One of the best experts on this subject based on the ideXlab platform.
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hadron production and phase changes in relativistic heavy ion collisions
European Physical Journal A, 2008Co-Authors: Jean Letessier, Johann RafelskiAbstract:We study soft hadron production in relativistic heavy-ion collisions in a wide range of reaction energy, 4.8 GeV \( \sqrt{{s_{{\rm NN}}}}\)≥200 GeV, we use continuity of particle yields and statistical parameters to predict the hadron production at \( \sqrt{{s_{{\rm NN}}}}\) = 62.4 GeV, and obtain total yields of hadrons at \( \sqrt{{s_{{\rm NN}}}}\) = 130 GeV. We consider, in depth, the pattern we uncover within the hadronization condition, and discuss possible mechanisms associated with the identified rapid change in system properties at \( \sqrt{{s_{{\rm NN}}^{{\rm cr}}}}\) . We propose that the chemically over-saturated 2 + 1 flavor hadron matter system undergoes a 1st-order phase transition.
