Landau Hydrodynamic Model Research Articles

Transverse Momentum and Pseudorapidity Spectrum of the Top Quark, Lepton, and b Jet in Proton-Proton Collisions at LHC

We study the transverse momentum and pseudorapidity spectrum of the top quark and their decay products, the t t ¯ system, and the total number of jets in proton-proton (pp) collisions at 13 TeV by using the Tsallis-Pareto-type function and the three-source Landau hydrodynamic model, respectively. The related parameters, such as the effective temperature of the interacting system ( T ), the nonextensivity of the process ( n ), and the width ( σ ) of pseudorapidity distribution, are extracted.

On pseudorapidity distribution in p-Pb and Xe–Xe collisions at high energy based on the three-source Landau hydrodynamic model

The pseudorapidity distributions of charged particles produced in p-Pb collisions and Xe-Xe collisions at LHC energies are described by the revised Landau hydrodynamic model. The research results are in agreement with the experimental data measured by ALICE collaboration at LHC. The related parameters are obtained and analyzed. And, we extracted the values of the squared speed of sound for central source are between 0.4 and 0.5.

Event patterns extracted from top quark-related spectra in proton-proton collisions at 8 TeV* * Supported by National Natural Science Foundation of China (11575103, 11747319), the Shanxi Provincial Natural Science Foundation (201701D121005), the Fund for Shanxi “1331 Project” Key Subjects Construction and the US DOE (DE-FG02-87ER40331.A008)

We analyze the transverse momentum (p T) and rapidity (y) spectra of top quark pairs, hadronic top quarks, and top quarks produced in proton-proton (pp) collisions at center-of-mass energy TeV. For spectra, we use the superposition of the inverse power-law suggested by the QCD (quantum chromodynamics) calculus and the Erlang distribution resulting from a multisource thermal model. For y spectra, we use the two-component Gaussian function resulting from the revised Landau hydrodynamic model. The modelling results are in agreement with the experimental data measured at the detector level, in the fiducial phase-space, and in the full phase-space by the ATLAS Collaboration at the Large Hadron Collider (LHC). Based on the parameter values extracted from p T and y spectra, the event patterns in three-dimensional velocity (βx -βy -βz ), momentum (px -py -pz ), and rapidity (y 1-y 2-y) spaces are obtained, and the probability distributions of these components are also obtained.

Event patterns extracted from anisotropic spectra of charged particles produced in Pb-Pb collisions at 2.76 TeV

Event patterns extracted from anisotropic spectra of charged particles produced in lead-lead collisions at 2.76 TeV are investigated. We use an inverse power-law resulted from the QCD calculus to describe the transverse momentum spectrum in the hard scattering process, and a revised Erlang distribution resulted from a multisource thermal model to describe the transverse momentum spectrum and anisotropic flow in the soft excitation process. The pseudorapidity distribution is described by a three-Gaussian function which is a revision of the Landau hydrodynamic model. Thus, the event patterns at the kinetic freeze-out are displayed by the scatter plots of the considered particles in the three-dimensional velocity, momentum, and rapidity spaces.

Event patterns (particle scatter plots) extracted from charged particle spectra in pp and Pb–Pb collisions at 2.76 TeV

The transverse momentum (pT) and pseudorapidity (η) spectra of charged particles produced in proton–proton (pp) and lead–lead (Pb-Pb) collisions at the Large Hadron Collider (LHC) are described by a hybrid model. In the model, the pT spectrum is described by a two-component distribution which contains an inverse power-law suggested by quantum chromodynamic calculus and an Erlang distribution resulted from a multisource thermal model. The η spectrum is described by a Gaussian rapidity (y) distribution resulted from the Landau hydrodynamic model and the two-component pT distribution, where the conversion between y and η is accurately considered. The modelling results are in agreement with the experimental data measured by the ATLAS Collaboration in pp collisions at center-of-mass energy TeV and in Pb–Pb collisions at center-of-mass energy per nucleon pair TeV. Based on the parameter values extracted from pT and η or y spectra, the event patterns or particle scatter plots in three-dimensional velocity and momentum spaces are obtained.

Extracting squared speed-of-sound parameter from asymmetric nuclear collisions at high energies

We apply the Landau hydrodynamic model in leading target/projectile nucleons and target/projectile cylinders in the multisource thermal model respectively, in asymmetric nuclear collisions. Each leading nucleon source or cylinder source is regarded as an energy reservoir to emit or produce particles and can be described by the Landau hydrodynamic model. The pseudorapidity distribution of final-state particles is in fact a sum of four Gaussian functions which correspond to the contributions of the leading target nucleons, target cylinder, projectile cylinder and leading projectile nucleons, respectively, in accordance with their central rapidities from low to high value. Based on the descriptions of the pseudorapidity distributions of final-state particles produced in proton-emulsion, deuteron-gold and gold-emulsion collisions, the squared speed-of-sound parameters for the four sources in asymmetric nuclear collisions have been extracted and shown to be approximately the same within the statistical error.

Searching for Minimum in Dependence of Squared Speed-of-Sound on Collision Energy

Experimental results of the rapidity distributions of negatively charged pions produced in proton-proton (p-p) and beryllium-beryllium (Be-Be) collisions at different beam momentums, measured by the NA61/SHINE Collaboration at the super proton synchrotron (SPS), are described by a revised (three-source) Landau hydrodynamic model. The squared speed-of-sound parametercs2is then extracted from the width of rapidity distribution. There is a local minimum (knee point) which indicates a softest point in the equation of state (EoS) appearing at about40A GeV/c(or 8.8 GeV) incs2excitation function (the dependence ofcs2on incident beam momentum (or center-of-mass energy)). This knee point should be related to the searching for the onset of quark deconfinement and the critical point of quark-gluon plasma (QGP) phase transition.

Event Patterns Extracted from Transverse Momentum and Rapidity Spectra ofZBosons and Quarkonium States Produced in pp and Pb-Pb Collisions at LHC

Transverse momentum (pT) and rapidity (y) spectra ofZbosons and quarkonium states (some charmoniumcc¯mesons such asJ/ψandψ(2S)and some bottomoniumbb¯mesons such asΥ(1S),Υ(2S), andΥ(3S)) produced in proton-proton (pp) and lead-lead (Pb-Pb) collisions at the large hadron collider (LHC) are uniformly described by a hybrid model of two-component Erlang distribution forpTspectrum and two-component Gaussian distribution foryspectrum. The former distribution results from a multisource thermal model, and the latter one results from the revised Landau hydrodynamic model. The modelling results are in agreement with the experimental data measured in pp collisions at center-of-mass energiess=2.76and 7 TeV and in Pb-Pb collisions at center-of-mass energy per nucleon pairsNN=2.76 TeV. Based on the parameter values extracted frompTandyspectra, the event patterns (particle scatter plots) in two-dimensionalpT-yspace and in three-dimensional velocity space are obtained.

On Distributions of Emission Sources and Speed-of-Sound in Proton-Proton (Proton-Antiproton) Collisions

The revised (three-source) Landau hydrodynamic model is used in this paper to study the (pseudo)rapidity distributions of charged particles produced in proton-proton and proton-antiproton collisions at high energies. The central source is assumed to contribute with a Gaussian function which covers the rapidity distribution region as wide as possible. The target and projectile sources are assumed to emit isotropically particles in their respective rest frames. The model calculations obtained with a Monte Carlo method are fitted to the experimental data over an energy range from 0.2 to 13 TeV. The values of the squared speed-of-sound parameter in different collisions are then extracted from the width of the rapidity distributions.

On Pseudorapidity Distribution and Speed of Sound in High Energy Heavy Ion Collisions Based on a New Revised Landau Hydrodynamic Model

We propose a new revised Landau hydrodynamic model to study systematically the pseudorapidity distributions of charged particles produced in heavy ion collisions over an energy range from a few GeV to a few TeV per nucleon pair. The interacting system is divided into three sources, namely, the central, target, and projectile sources, respectively. The large central source is described by the Landau hydrodynamic model and further revised by the contributions of the small target/projectile sources. The modeling results are in agreement with the available experimental data at relativistic heavy ion collider, large hadron collider, and other energies for different centralities. The value of square speed of sound parameter in different collisions has been extracted by us from the widths of rapidity distributions. Our results show that, in heavy ion collisions at energies of the two colliders, the central source undergoes a phase transition from hadronic gas to quark-gluon plasma liquid phase; meanwhile, the target/projectile sources remain in the state of hadronic gas. The present work confirms that the quark-gluon plasma is of liquid type rather than being of a gas type.

Pseudorapidity distributions of charged particles produced in p–p collisions at center-of-mass energies from 23.6 GeV to 900 GeV

In p–p collisions there are two leading particles, one in the projectile and the other in the target fragmentation region. In this paper we show that, just like in nucleus–nucleus collisions, the revised Landau hydrodynamic model alone does not provide a good enough description of the measured pseudorapidity distributions of charged particles produced in p–p collisions. Only after the leading particles are taken into account can the experimental data be properly matched with the theoretical model in the entire available energy region from [Formula: see text] to 900 GeV.

Pseudorapidity distributions of the produced charged particles in nucleus-nucleus collisions at low energies at the BNL relativistic heavy ion collider

The revised Landau hydrodynamic model is used to discuss the pseudorapidity distributions of the produced charged particles in Au+Au and Cu+Cu collisions at energies of √sNN = 19.6 and 22.4 GeV respectively at the BNL Relativistic Heavy Ion Collider. It is found that the revised Landau hydrodynamic model alone can give a good description of the experimental measurements. This is different from the result with the same collisions but at the maximum energy of √sNN = 200 GeV, where in addition to the revised Landau hydrodynamic model, the effects of leading particles have to be taken into account in order to explain the experimental observations. This can be attributed to the different degrees of transparency of participants at the different incident energies.

Hydrodynamic description for the pseudorapidity distributions of the charged particles produced in nucleus+nucleus collisions at high energy

By using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of the charged particles produced in high-energy heavy-ion collisions. The leading particles are assumed to have the rapidity distributions with Gaussian forms with the normalization constant being equal to the number of participants, which can be figured out in theory. The results from the revised Landau hydrodynamic model, together with the contributions from leading particles, were found to be consistent with the experimental data obtained by the PHOBOS Collaboration on RHIC (Relativistic Heavy Ion Collider) at BNL (Brookhaven National Laboratory) in different centrality Cu+Cu and Au+Au collisions at high energies.

Pseudorapidity Distribution of Charged Particles and Square Speed of Sound Parameter inp-porp-p-Collisions over an Energy Range from 0.053 to 7 TeV

Pseudorapidity distributions of charged particles produced in proton-proton (p-p) or proton-antiproton (p-p-) collisions over an energy range from 0.053 to 7 TeV are studied by using the four-component Landau hydrodynamic model. The results calculated by the model are in agreement with the experimental data of the UA5, PHOBOS, UA1, P238, CDF, ALICE, and CMS Collaborations which present orderly from low to high energies. According to the distribution widths of different components, the values and some features of square speed of sound parametercs2for “participant” and “spectator” quark components are obtained. It is shown that the speed of sound for “participant” quark components agrees approximately with that for “spectator” quark components in the error ranges. The present work is useful for studying nucleus-nucleus collisions in the related energy range.

THE HYDRODYNAMIC DESCRIPTION OF THE ENERGY AND CENTRALITY DEPENDENCES OF THE PSEUDORAPIDITY DISTRIBUTIONS OF THE PRODUCED CHARGED PARTICLES INAu+AuCOLLISIONS

By using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of produced charged particles in high energy heavy-ion collisions. The charged particles resulted from the freeze-out of the matter produced in collisions possess the Gaussian-like rapidity distributions. The leading particles are assumed having the rapidity distributions of the Gaussian form with the normalization constant being equal to the number of participants, which can be figured out in theory. It is found that the results from the revised Landau hydrodynamic model together with the contributions from leading particles are well consistent with the experimental data carried out by BNL-RHIC-PHOBOS Collaboration in different centrality Au + Au collisions at energies of [Formula: see text], 130 and 62.4 GeV , respectively.

Revised Landau hydrodynamic model and the pseudorapidity distributions of charged particles produced in nucleus-nucleus collisions at maximum energy at the BNL Relativistic Heavy Ion Collider

By using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of produced charged particles in nucleus-nucleus collisions at high energy. The theoretical results are in good agreement with the experimental measurements carried out by PHOBOS Collaboration in different centrality Au+Au and Cu+Cu collisions at the maximum energy of $\sqrt{{s}_{\mathrm{NN}}}=200\phantom{\rule{0.28em}{0ex}}\mathrm{GeV}$ at the BNL Relativistic Heavy Ion Collider.

Speed of Sound Parameter from RHIC and LHC Heavy-Ion Data

In framework of combing the participant-spectator model and the Landau hydrodynamic model, the pseudorapidity distributions of charged particles produced in heavy-ion (or nucleus-nucleus) collisions at RHIC and LHC energies are described by a modified Landau hydrodynamic model, where the Landau hydrodynamic model is applied to the target/projectile spectators and the target/projectile participants, respectively. The modeling results are in agreement with the PHOBOS and ALICE experimental data. Then, the values of square speed of sound (cs2) for the participants and spectators can be obtained from the widths of charged particle pseudorapidity distributions. Some features ofcs2for different centralities and center-of-mass energies are obtained too.

The revised Landau hydrodynamic model and the pseudorapidity distributions of produced charged particles in high energy heavy ion collisions

Using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of produced charged particles in high energy heavy ion collisions. As usual, the leading particles here mean the particles which inherit the quantum numbers of colliding nucleons and carry off most parts of the incident energy. We argue that the rapidity distributions of leading particles have the Gaussian form with the normalization constant being equal to the number of participants. We find that the results from the hydrodynamic model alone are not consistent with the experimental data carried out by BNL-RHIC-PHOBOS Collaboration in Au + Au collisions at . Only after the contributions from leading particles are included, can the experimental measurements be described well.

Landau Hydrodynamics and RHIC Phenomena

The basic physical assumptions and results of Landau's hydrodynamic model of particle production are reviewed. It is argued that these results have a substantial descriptive and predictive power in strong-interaction phenomenology, including recent RHIC data.

Fluctuations in hadronic and nuclear collisions

We investigate several fluctuation effects in high-energy hadronic and nuclear collisions through the analysis of different observables. To introduce fluctuations in the initial stage of collisions, we use the Interacting Gluon Model (IGM) modified by the inclusion of the impact parameter. The inelasticity and leading-particle distributions follow directly from this model. The fluctuation effects on rapidity distributions are then studied by using Landau's Hydrodynamic Model in one dimension. To investigate further the effects of the multiplicity fluctuation, we use the Longitudinal Phase-Space Model, with the multiplicity distribution calculated within the hydrodynamic model, and the initial conditions given by the IGM. Forward-backward correlation is obtained in this way.