scholarly journals Out-Of-Equilibrium Transverse Momentum Spectra of Pions at LHC Energies

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Abdel Nasser Tawfik
Keyword(s):  
Transverse Momentum ◽  
Entire Range ◽  
Pion Production ◽  
Ad Hoc ◽  
Chemical Potential ◽  
Alice Experiment ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Bose Einstein

In order to characterize the transverse momentum spectra (pT) of positive pions measured in the ALICE experiment, two thermal approaches are utilized; one is based on degeneracy of nonperfect Bose-Einstein gas and the other imposes an ad hoc finite pion chemical potential. The inclusion of missing hadron states and the out-of-equilibrium contribute greatly to the excellent characterization of pion production. An excellent reproduction of these pT-spectra is achieved at μπ=0.12 GeV and this covers the entire range of pT. The excellent agreement with the experimental results can be understood as a manifestation of not-yet-regarded anomalous pion production, which likely contributes to the long-standing debate on “anomalous” proton-to-pion ratios at top RHIC and LHC energies.

scholarly journals Coulomb Interaction Effects on Pion Production in Au+Au Collisions at Relativistic Energies

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Catalin Ristea ◽  
Oana Ristea ◽  
Alexandru Jipa
Keyword(s):  
Transverse Momentum ◽  
Coulomb Interaction ◽  
Beam Energy ◽  
Pion Production ◽  
Charged Pion ◽  
Centrality Dependence ◽  
Central Collisions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Coulomb Effects

Coulomb effects on charged pion transverse momentum spectra measured in Au+Au collisions at RHIC-BES energies are investigated. From these spectra the π-/π+ ratios as a function of transverse momentum are obtained and used to extract the “Coulomb kick”, pc (a momentum change due to the Coulomb interaction), and initial pion ratio for three different collision energies and various centrality classes. The Coulomb kick shows a decrease with the increase of beam energy and a clear centrality dependence, with larger values for the most central collisions. The results are connected with the kinetic freeze-out dynamics.

scholarly journals Transverse Momentum Distributions of Hadrons Produced in Pb-Pb Collisions at LHC EnergysNN=2.76TeV

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Saeed Uddin ◽  
Inam-ul Bashir ◽  
Riyaz Ahmed Bhat
Keyword(s):  
Experimental Data ◽  
Transverse Momentum ◽  
Chemical Potential ◽  
Particle Density ◽  
Strong Increase ◽  
Collective Flow ◽  
Alice Experiment ◽  
Particle Species ◽  
Transverse Momentum Spectra ◽  
Freeze Out

The transverse momentum spectra of several types of hadrons,p,p̅,K+,K-,Ks0,Λ,Ω,Ω̅,Ξ-, andΞ̅produced in most central Pb-Pb collisions at LHC energysNN=2.76 TeV have been studied at midrapidity (|y|<0.5) using an earlier proposed unified statistical thermal freeze-out model. The calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment at LHC. The model calculation fits provide the thermal freeze-out conditions in terms of the temperature and collective flow effect parameters for different particle species. Interestingly the model parameter fits to the experimental data reveal stronger collective flow in the system and lesser freeze-out temperatures of the different particle species as compared to Au-Au collisions at RHIC. The strong increase of the collective flow appears to be a consequence of the increasing particle density at LHC. The model used incorporates a longitudinal as well as transverse hydrodynamic flow. The chemical potential has been assumed to be nearly equal to zero for the bulk of the matter owing to high degree of nuclear transparency effect at such collision energies. The contributions from heavier decay resonances are also taken into account.

scholarly journals Centrality dependence of thermal freeze-out conditions at LHC in Pb+Pb collisions at sNN = 2.76TeV

2015 ◽  
Vol 30 (33) ◽  
pp. 1550167 ◽  
Author(s):  
Saeed Uddin ◽  
Inam-ul Bashir ◽  
Riyaz Ahmed Bhat ◽  
Waseem Bashir
Keyword(s):  
Experimental Data ◽  
Chemical Potential ◽  
Heavy Ion ◽  
Collective Flow ◽  
Flow Profile ◽  
Alice Experiment ◽  
Ion Collisions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Freeze Out

We have analyzed the available midrapidity [Formula: see text] transverse momentum spectra of identified particles such as protons [Formula: see text], kaons [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] for different centralities of Pb+Pb collisions at the LHC energy [Formula: see text]. We have used our earlier proposed unified statistical thermal freeze-out model. The model incorporates the effect of nuclear transparency in such energetic collisions and the resulting asymmetry in the collective-flow profile along the longitudinal and the transverse directions. Our calculated results are found to be in good agreement with the experimental data measured by the ALICE experiment. The model calculation fits the experimental data for different particle species which provide thermal freeze-out conditions in terms of temperature and collective-flow parameters. The analysis shows a rise in the thermal freeze-out temperature and a mild decrease in the transverse collective-flow velocity as we go from central to the peripheral collisions. The baryon chemical potential is assumed to be nearly zero for the bulk of the matter [Formula: see text], a situation expected in the heavy ion collisions at LHC energies in the Bjorken approach owing to nearly complete nuclear transparency. The contributions from the decay of the heavier resonances are also taken into account in our calculations.

scholarly journals Energy and multiplicity dependence of hadronic resonance production with ALICE at the LHC

2020 ◽  
Vol 1643 (1) ◽  
pp. 012007
Author(s):  
Angela Badalà
Keyword(s):  
Transverse Momentum ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Pp Collisions ◽  
Alice Experiment ◽  
Ion Collisions ◽  
Scattering Effects ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Hadronic Resonances

Abstract The study of hadronic resonances plays an important role both in pp and in heavy-ion collisions. Since the lifetimes of short-lived resonances are comparable with the lifetime of the fireball formed in heavy-ion collisions, regeneration and re-scattering effects can modify the measured yields, especially at low transverse momentum. Measurements in pp collisions at different energies constitute a baseline for studies in heavy-ion collisions and provide constraints for tuning QCD-inspired event generators. Furthermore, high multiplicity pp collisions, where the density and the volume of the system are expected to be larger compared to minimum bias pp collisions, can help in the search for the onset of collective phenomena. Here we present recent results on short-lived hadronic resonances obtained by the ALICE experiment at LHC energies in different collision systems (pp, p–Pb and Pb–Pb) including new results obtained in Xe–Xe collisions. The ALICE results on transverse momentum spectra, yields and their ratios to long-lived particles will be discussed.

scholarly journals Transverse momentum spectra and nuclear modification factors of identified charged hadrons in p-Pb and Pb-Pb collisions at √sNN = 5.02 TeV with ALICE

2018 ◽  
Vol 182 ◽  
pp. 02126
Author(s):  
Maria Vasileiou
Keyword(s):  
Transverse Momentum ◽  
Lower Energy ◽  
Initial State ◽  
Alice Experiment ◽  
Strong Suppression ◽  
Nuclear Modification ◽  
Wide Range ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Nuclear Modification Factors

The ALICE experiment has measured the production of identified light-flavour hadrons in p-Pb and Pb-Pb collisions at 5.02 TeV in a wide range of transverse momentum. The newest ALICE results on pion, kaon and proton transverse momentum spectra, yield ratios and nuclear modification factors will be presented and discussed in comparison to lower energy results. In particular, the production of identified hadrons in most central Pb-Pb collisions relative to pp collisions is found to be strongly suppressed at high transverse momenta (pT > 8 GeV/c) whereas in p-Pb collisions the nuclear modification factors are consistent with unity. This indicates that the strong suppression of high-pT hadrons measured in central Pb-Pb collisions is not due to an initial state effect but instead to the energy loss of partons traversing a hot and dense QCD medium.

scholarly journals Hadronic resonance production with ALICE at the LHC

2019 ◽  
Vol 204 ◽  
pp. 03015
Author(s):  
Sergey Kiselev
Keyword(s):  
Transverse Momentum ◽  
Resonance Production ◽  
Alice Experiment ◽  
Nuclear Modification ◽  
Model Predictions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Nuclear Modification Factors ◽  
Hadronic Resonances

We present recent results on short-lived hadronic resonances obtained in the ALICE experiment at LHC energies, including results from the Xe-Xe run. The ALICE results on transverse momentum spectra, yields, their ratio to long-lived particles, and nuclear modification factors will be discussed. The results will be compared with model predictions and measurements at lower energies.

Identified charged particle distributions in Au + Au collisions at s NN = 9.2GeV

2015 ◽  
Vol 30 (24) ◽  
pp. 1550139 ◽  
Author(s):  
Inam-ul Bashir ◽  
Saeed Uddin ◽  
Riyaz Ahmed Bhat ◽  
Waseem Bashir
Keyword(s):  
Transverse Momentum ◽  
Chemical Potential ◽  
Center Of Mass ◽  
Particle Distributions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Star Experiment ◽  
Mass Frame ◽  
Data Points ◽  
Freeze Out

Midrapidity results on multiplicity density [Formula: see text] and transverse momentum distributions [Formula: see text] of pions, kaons and protons in Au + Au collisions at [Formula: see text] are reproduced by using our earlier proposed Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in fairly good agreement with the experimental data points taken from STAR experiment. Freeze-out conditions in terms of a transverse flow velocity parameter and the thermal freeze-out temperature are extracted from the fits of transverse momentum spectra of the particles at different collision centralities. A large value of midrapidity chemical potential reveals the effects of almost complete stopping in the center-of-mass frame of the system produced. The resonance decay contributions are found to have a negligible effect on the transverse momentum spectra of the particles while these are found to be significant for determining the shape of the rapidity spectra.

scholarly journals On Descriptions of Particle Transverse Momentum Spectra in High Energy Collisions

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Fu-Hu Liu ◽  
Ya-Qin Gao ◽  
Hua-Rong Wei
Keyword(s):  
Transverse Momentum ◽  
High Energy ◽  
Emission Source ◽  
Angular Distributions ◽  
Nuclear Collisions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Tsallis Distribution ◽  
High Energy Collisions ◽  
Bose Einstein

The transverse momentum spectra obtained in the frame of an isotropic emission source are compared in terms of Tsallis, Boltzmann, Fermi-Dirac, and Bose-Einstein distributions and the Tsallis forms of the latter three standard distributions. It is obtained that, at a given set of parameters, the standard distributions show a narrower shape than their Tsallis forms which result in wide and/or multicomponent spectra with the Tsallis distribution in between. A comparison among the temperatures obtained from the distributions is made with a possible relation to the Boltzmann temperature. An example of the angular distributions of projectile fragments in nuclear collisions is given.

scholarly journals Study of Dependence of Kinetic Freezeout Temperature on the Production Cross-Section of Particles in Various Centrality Intervals in Au–Au and Pb–Pb Collisions at High Energies

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 488
Author(s):  
Muhammad Waqas ◽  
Guang-Xiong Peng
Keyword(s):  
Transverse Momentum ◽  
Flow Velocity ◽  
Production Cross ◽  
Center Of Mass ◽  
Wave Model ◽  
Transverse Flow ◽  
Peripheral Collisions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Transverse Flow Velocity

Transverse momentum spectra of π+, p, Λ, Ξ or Ξ¯+, Ω or Ω¯+ and deuteron (d) in different centrality intervals in nucleus–nucleus collisions at the center of mass energy are analyzed by the blast wave model with Boltzmann Gibbs statistics. We extracted the kinetic freezeout temperature, transverse flow velocity and kinetic freezeout volume from the transverse momentum spectra of the particles. It is observed that the non-strange and strange (multi-strange) particles freezeout separately due to different reaction cross-sections. While the freezeout volume and transverse flow velocity are mass dependent, they decrease with the resting mass of the particles. The present work reveals the scenario of a double kinetic freezeout in nucleus–nucleus collisions. Furthermore, the kinetic freezeout temperature and freezeout volume are larger in central collisions than peripheral collisions. However, the transverse flow velocity remains almost unchanged from central to peripheral collisions.

scholarly journals Analyzing Transverse Momentum Spectra of Pions, Kaons and Protons in p–p, p–A and A–A Collisions via the Blast-Wave Model with Fluctuations

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 803
Author(s):  
Hai-Ling Lao ◽  
Fu-Hu Liu ◽  
Bo-Qiang Ma
Keyword(s):  
Transverse Momentum ◽  
Flow Velocity ◽  
Blast Wave ◽  
Proper Time ◽  
Wave Model ◽  
Transverse Flow ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Transverse Flow Velocity ◽  
Freeze Out

The transverse momentum spectra of different types of particles, π±, K±, p and p¯, produced at mid-(pseudo)rapidity in different centrality lead–lead (Pb–Pb) collisions at 2.76 TeV; proton–lead (p–Pb) collisions at 5.02 TeV; xenon–xenon (Xe–Xe) collisions at 5.44 TeV; and proton–proton (p–p) collisions at 0.9, 2.76, 5.02, 7 and 13 TeV, were analyzed by the blast-wave model with fluctuations. With the experimental data measured by the ALICE and CMS Collaborations at the Large Hadron Collider (LHC), the kinetic freeze-out temperature, transverse flow velocity and proper time were extracted from fitting the transverse momentum spectra. In nucleus–nucleus (A–A) and proton–nucleus (p–A) collisions, the three parameters decrease with the decrease of event centrality from central to peripheral, indicating higher degrees of excitation, quicker expansion velocities and longer evolution times for central collisions. In p–p collisions, the kinetic freeze-out temperature is nearly invariant with the increase of energy, though the transverse flow velocity and proper time increase slightly, in the considered energy range.

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