Searcharxiv⌕ Search

arXiv subjects

J. Cleymans

Publications and source records attributed to J. Cleymans.

At least 37 records · Page 2Linked to original sources

Strangeness enhancement at the hadronic chemical freeze-out

The chemical freeze-out of hadrons created in the high energy nuclear collisions is studied within the realistic version of the hadron resonance gas model. The chemical non-equilibrium of strange particles is accounted via the usual $γ_{s}$ factor which gives us an opportunity to perform a high quality fit with $χ^2/dof \simeq 63.5/55 \simeq 1.15$ of the hadronic multiplicity ratios measured from the low AGS to the highest RHIC energies. In contrast to previous findings, at low energies we observe the strangeness enhancement instead of a suppression. In addition, the performed $γ_{s}$ fit allows us to achieve the highest quality of the Strangeness Horn description with $χ^2/dof=3.3/14$. For the first time the top point of the Strangeness Horn is perfectly reproduced, which makes our theoretical horn as sharp as an experimental one. However, the $γ_{s}$ fit approach does not sizably improve the description of the multi-strange baryons and antibaryons. Therefore, an apparent deviation of multi-strange baryons and antibaryons from chemical equilibrium requires further explanation.

hep-ph↗

Chemical freeze-outs of strange and non-strange particles and residual chemical non-equilibrium

We propose an elaborate version of the hadron resonance gas model with the combined treatment of separate chemical freeze-outs for strange and non-strange hadrons and with an additional γ_{s} factor which accounts for the remaining strange particle non-equilibration. Two sets of chemical freeze-outs parameters are connected by the conservation laws of entropy, baryonic charge, isospin projection and strangeness. The developed approach enables us to perform a high-quality fit of the hadron multiplicity ratios for AGS, SPS and RHIC energies with total χ^2/dof \simeq 1.05. A special attention is paid to a complete description of the Strangeness Horn. A well-known \bar p, \bar Λand \bar Ξselective suppression problem is also discussed.

hep-ph↗

Transverse Momentum Distributions in p-Pb collisions and Tsallis Thermodynamics

The transverse momentum distributions of charged particles in p-Pb collisions as sqrt{s_{NN}} = 5.02 TeV measured by the ALICE collaboration are fitted using Tsallis statistics. The use of a thermodynamically consistent form of this distribution leads to an excellent description of the transverse momentum distributions for all rapidity intervals. The values of the Tsallis parameter q, the temperature T and the radius R of the system do not change within the measured pseudorapidity intervall.

hep-ph↗

Transverse Momentum Distributions at the LHC and Tsallis Thermodynamics

An overview is presented of transverse momentum distributions of particles at the LHC using the Tsallis distribution. The use of a thermodynamically consistent form of this distribution leads to an excellent description of charged and identified particles. The values of the Tsallis parameter q are truly remarkably consistent.

hep-ph↗

Systematic Properties of the Tsallis Distribution: Energy Dependence of Parameters

Changes in the transverse momentum distributions with beam energy are studied using the Tsallis distribution as a parameterization. The dependence of the Tsallis parameters q, T and the volume on beam energy is determined. The Tsallis parameter q shows a weak but clear increase with beam energy with the highest value being approximately 1.15. The Tsallis temperature and volume are consistent with being independent of beam energy within experimental uncertainties.

hep-ph↗

Chemical Freeze-out of Strange Particles and Possible Root of Strangeness Suppression

Two approaches to treat the chemical freeze-out of strange particles in hadron resonance gas model are analyzed. The first one employs their non-equillibration via the usual γ_s factor and such a model describes the hadron multiplicities measured in nucleus-nucleus collisions at AGS, SPS and RHIC energies with χ^2/dof = 1.15. Surprisingly, at low energies we find not the strangeness suppression, but its enhancement. Also we suggest an alternative approach to treat the strange particle freeze-out separately, but with the full chemical equilibration. This approach is based on the conservation laws which allow us to connect the freeze-outs of strange and non-strange hadrons. Within the suggested approach the same set of hadron multiplicities can be described better than within the conventional approach with χ^2/dof = 1.06. Remarkably, the fully equilibrated approach describes the strange hyperons and antihyperons much better than the conventional one.

hep-ph↗

Systematic properties of the Tsallis Distribution: Energy Dependence of Parameters in High-Energy p-p Collisions

Changes in the transverse momentum distributions with beam energy are studied using the Tsallis distribution as a parameterization. The dependence of the Tsallis parameters q, T and the volume are determined as a function of beam energy. The Tsallis parameter q shows a weak but clear increase with beam energy with the highest value being approximately 1.15. The Tsallis temperature and volume are consistent with being independent of beam energy within experimental uncertainties.

hep-ph↗

Nonequilibrium distribution functions of nucleons in relativistic nucleus-nucleus collisions

The collision smearing of the nucleon momenta about their initial values during relativistic nucleus-nucleus collisions is investigated. To a certain degree, our model belongs to the transport type, and we investigate the evolution of the nucleon system created at a nucleus-nucleus collision. However, we parameterize this development by the number of collisions of every particle during evolution rather than by the time variable. It is assumed that the group of nucleons which leave the system after the same number of collisions can be joined in a particular statistical ensemble. The nucleon nonequilibrium distribution functions, which depend on a certain number of collisions of a nucleon before freeze-out, are derived.

nucl-th↗

The Tsallis Distribution at the LHC

The Tsallis distribution has been used widely in high energy physics to describe the transverse momnetum distributions of particles. In this note we show that the use of a thermodynamically consistent form of this distribution leads to a description of identified particles with the same values of the temperature $T$ and the parameter $q$.

hep-ph↗

Relativistic Thermodynamics: Transverse Momentum Distributions in High-Energy Physics

Transverse momentum distributions measured by the STAR and PHENIX collaborations at the Relativistic Heavy Ion Collider and by the ALICE, ATLAS and CMS collaborations at the Large Hadron Collider can be considered in the framework of relativistic thermodynamics using the Tsallis distribution. Theoretical issues are clarified concerning the thermodynamic consistency in the case of relativistic high energy quantum distributions. An improved form is proposed for describing the transverse momentum distribution and fits are presented together with estimates of the parameter q and the temperature T.

hep-ph↗

The Thermal Model at the Large Hadron Collider

A discussion is presented of results with identified particles at the Large Hadron Collider. Possible deviations from the standard statistical distributions are investigated by considering in detail results obtained using the Tsallis distribution. Matter-antimatter production is discussed within the framework of chemical equilibrium in \pp and heavy ion collisions.

hep-ph↗

The Tsallis Distribution in Proton-Proton Collisions at $\sqrt{s}$ = 0.9 TeV at the LHC

The Tsallis distribution has been used recently to fit the transverse momentum distributions of identified particles by the STAR and PHENIX collaborations at the Relativistic Heavy Ion Collider and by the ALICE and CMS collaborations at the Large Hadron Collider. Theoretical issues are clarified concerning the thermodynamic consistency of the Tsallis distribution in the particular case of relativistic high energy quantum distributions. An improved form is proposed for describing the transverse momentum distribution and fits are presented together with estimates of the parameter $q$ and the temperature $T$.

hep-ph↗

Chiral condensate and Mott-Anderson freeze-out

We present the idea of a Mott-Anderson freeze-out that suggests a key role of the localization of the hadron wave functions when traversing the hadronization transition. The extension of hadron wave functions in dense matter is governed by the behavior of the chiral quark condensate such that its melting at finite temperatures and chemical potentials entails an increase of the size of hadrons and thus their geometrical strong interaction cross sections. It is demonstrated within a schematic resonance gas model, that a kinetic freeze-out condition reveals a correlation with the reduction of the chiral condensate in the phase diagram up to 50 % of its vacuum value. Generalizing the description of the chiral condensate by taking into account a full hadron resonance gas such correlation gets distorted. We discuss, that this may be due to our approximations in calculating the chiral condensate which disregard both, in-medium effects on hadron masses and hadron-hadron interactions. The latter, in particular due to quark exchange reactions, could lead to a delocalization of the hadron wave functions in accordance with the picture of a Mott-Anderson transition.

hep-ph↗

THERMUS

THERMUS is a package of C++ classes and functions allowing statistical-thermal model analyses of particle production in relativistic heavy-ion collisions to be performed within the ROOT framework of analysis. Calculations are possible within three statistical ensembles; a grand-canonical treatment of the conserved charges $B$, $S$ and $Q$, a fully canonical treatment of the conserved charges, and a mixed-canonical ensemble combining a canonical treatment of strangeness with a grand-canonical treatment of baryon number and electric charge. THERMUS allows for the assignment of decay chains and detector efficiencies specific to each particle yield, which enables sensible fitting of model parameters to experimental data.

hep-ph↗

The Tsallis Distribution and Transverse Momentum Distributions in High-Energy Physics

The Tsallis distribution has been used recently to fit the transverse momentum distributions of identified particles by the STAR collaboration \cite{Abelev:2006cs} at the Relativistic Heavy Ion Collider and by the ALICE \cite{Aamodt:2011zj} and CMS \cite{Khachatryan:2011tm} collaborations at the Large Hadron Collider. Theoretical issues are clarified concerning the thermodynamic consistency of the Tsallis distribution in the particular case of relativistic high energy quantum distributions. An improved form is proposed for describing the transverse momentum distribution and fits are presented together with estimates of the parameter $q$ and the temperature $T$.

hep-ph↗

Antimatter production in proton-proton and heavy-ion collisions at ultrarelativistic energies

One of the striking features of particle production at high beam energies is the near equal abundance of matter and antimatter in the central rapidity region. In this paper we study how this symmetry is reached as the beam energy is increased. In particular, we quantify explicitly the energy dependence of the approach to matter/antimatter symmetry in proton-proton and in heavy-ion collisions. Expectations are presented also for the production of more complex forms of antimatter like antihypernuclei.

hep-ph↗

Dynamical and thermal descriptions in parton distribution functions

We suggest a duality between the standard (dynamical) and statistical distributions of partons in the nucleons. The temperature parameter entering into the statistical form for the quark distributions is estimated. It is found that this effective temperature is practically the same for the dependence on longitudinal and transverse momenta and, in turn, it is close to the freeze-out temperature in high energy heavy-ion collisions.

hep-ph↗