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 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 Particle Transverse Momentum Distributions in p-p Collisions at √sNN=0.9 TeV

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Inam-ul Bashir ◽  
Rameez Ahmad Parra ◽  
Riyaz Ahmed Bhat ◽  
Saeed Uddin
Keyword(s):  
Transverse Momentum ◽  
Collective Flow ◽  
Model Calculations ◽  
Flow Parameters ◽  
Momentum Distributions ◽  
Momentum Spectra ◽  
Rapidity Distributions ◽  
Transverse Momentum Spectra ◽  
Good Agreement ◽  
Freeze Out

The midrapidity transverse momentum spectra of hadrons (p, K+, Ks0, ϕ, Λ, and (Ξ-+Ξ--)) and the available rapidity distributions of the strange hadrons (Ks0, (Λ+Λ-), (Ξ-+Ξ--)) produced in p-p collisions at LHC energy √sNN = 0.9 TeV have been studied using a Unified Statistical Thermal Freeze-out Model (USTFM). The calculated results are found to be in good agreement with the experimental data. The theoretical fits of the transverse momentum spectra using the model calculations provide the thermal freeze-out conditions in terms of the temperature and collective flow parameters for different hadronic species. The study reveals the presence of a significant collective flow and a well-defined temperature in the system thus indicating the formation of a thermally equilibrated hydrodynamic system in p-p collisions at LHC. Moreover, the fits to the available experimental rapidity distributions data of strange hadrons show the effect of almost complete transparency in p-p collisions at LHC. The model incorporates longitudinal as well as a transverse hydrodynamic flow. The contributions from heavier decay resonances have also been taken into account. We have also imposed the criteria of exact strangeness conservation in the system.

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 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.

Centrality and rapidity dependences of negative pions in He–C collisions at 4.2 A GeV/c

2019 ◽  
Vol 34 (12) ◽  
pp. 1950092
Author(s):  
Akhtar Iqbal ◽  
Khusniddin Olimov ◽  
Mushtaq Ahmad ◽  
Ali Zaman ◽  
Obaidullah Jan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Transverse Momentum ◽  
String Model ◽  
Research Paper ◽  
Weak Dependence ◽  
Mathematical Functions ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Two Temperature ◽  
Alpha Carbon

In the current research paper, we investigated the dependence of [Formula: see text] spectra of [Formula: see text] mesons on centrality of collision and different rapidity [Formula: see text] range. These negative pions are produced in Alpha–Carbon collisions at a momentum of 4.2 A GeV/c. We used Boltzmann and Hagedorn functions for one and two temperature fitting, of transverse momentum spectra obtained from experimental data and Model (Quark Gluon String Model, QGSM) data. By fitting these mathematical functions, we analyzed the change in shape of slopes of [Formula: see text] spectra. The fitting results for spectral temperatures were consistently larger (both in the experiment and QGSM) for the [Formula: see text] spectra of negative pions produced in range of mid-rapidity in comparison with those produced in fragmentation regions of colliding nuclei. It was also observed that extracted spectral temperatures from experimental data have a weak dependence on the collision centrality. The pion spectra can be described nicely by fitting two temperature functions for the experimental [Formula: see text] spectra for whole range and for the interval [Formula: see text]. In the [Formula: see text] range of [Formula: see text], one temperature functions were found sufficient for fitting the experimental [Formula: see text] spectra. The extracted temperatures from experimental data were found more sensitive to the fitting range of [Formula: see text], in contrast with temperatures obtained from QGSM data.

Combined analysis of midrapidity transverse momentum spectra of the charged pions and kaons, protons and antiprotons in p+p and Pb+Pb collisions at (snn)1/2 = 2.76 and 5.02 TeV at the LHC

2020 ◽  
Vol 35 (29) ◽  
pp. 2050237
Author(s):  
Khusniddin K. Olimov ◽  
Shakhnoza Z. Kanokova ◽  
Alisher K. Olimov ◽  
Kobil I. Umarov ◽  
Boburbek J. Tukhtaev ◽  
...  
Keyword(s):  
Transverse Momentum ◽  
Center Of Mass ◽  
Heavy Ion ◽  
Transverse Flow ◽  
Alice Collaboration ◽  
Momentum Spectra ◽  
Charged Pions ◽  
Transverse Momentum Spectra ◽  
Tsallis Distribution ◽  
Freeze Out

The experimental transverse momentum spectra of the charged pions and kaons, protons and antiprotons, produced at midrapidity in [Formula: see text] collisions at [Formula: see text] and 5.02 TeV, central (0–5%) and peripheral (60–80%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] TeV, central (0–5%), semicentral (40–50%) and peripheral (80–90%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] TeV, measured by ALICE collaboration, were analyzed using the Tsallis distribution function as well as Hagedorn formula with the embedded transverse flow. To exclude the influence (on the results) of different available fitting [Formula: see text] ranges in the analyzed collisions, we compare the results obtained from combined (simultaneous) fits of midrapidity spectra of the charged pions and kaons, protons and antiprotons with the above theoretical model functions using the identical fitting [Formula: see text] ranges in [Formula: see text] as well as Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV. Using the combined fits with the thermodynamically consistent Tsallis distribution as well as the simple Tsallis distribution without thermodynamical description, it is obtained that the global temperature [Formula: see text] and non-extensivity parameter [Formula: see text] slightly increase (consistently for all the particle types) with an increase in center-of-mass (c.m.) energy [Formula: see text] of [Formula: see text] collisions from 2.76 TeV to 5.02 TeV, indicating that the more violent and faster [Formula: see text] collisions at [Formula: see text] TeV result in a smaller degree of thermalization (higher degree of non-equilibrium) compared to that in [Formula: see text] collisions at [Formula: see text] TeV. The [Formula: see text] values for pions and kaons proved to be very close to each other, whereas [Formula: see text] for protons and antiprotons proved to be significantly lower than that for pions and kaons, that is [Formula: see text]. The results of the combined fits using Hagedorn formula with the embedded transverse flow are consistent with practically no (zero) transverse (radial) flow in [Formula: see text] collisions at [Formula: see text] and 5.02 TeV. Using Hagedorn formula with the embedded transverse flow, it is obtained that the value of the (average) transverse flow velocity increases and the temperature [Formula: see text] decreases with an increase in collision centrality in Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV, which is in good agreement with the results of the combined Boltzmann–Gibbs blast-wave fits to the particle spectra in Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV in recent works of ALICE collaboration. The temperature [Formula: see text] parameter, which approximates the kinetic freeze-out temperature, was shown to coincide in central (0–5%) Pb[Formula: see text]+[Formula: see text]Pb collisions at [Formula: see text] and 5.02 TeV, which implies, taking into account the results of our previous analysis, that kinetic freeze-out temperature stays practically constant in central heavy-ion collisions in [Formula: see text] GeV energy range.

scholarly journals Comparing the Tsallis Distribution with and without Thermodynamical Description inp+pCollisions

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
H. Zheng ◽  
Lilin Zhu
Keyword(s):  
Experimental Data ◽  
Transverse Momentum ◽  
Transverse Energy ◽  
Transverse Mass ◽  
Heavy Particles ◽  
Momentum Spectra ◽  
Transverse Momentum Spectra ◽  
Extra Factor ◽  
Particle Spectra ◽  
Tsallis Distribution

We compare two types of Tsallis distribution, that is, with and without thermodynamical description, using the experimental data from the STAR, PHENIX, ALICE, and CMS Collaborations on the rapidity and energy dependence of the transverse momentum spectra inp+pcollisions. Both of them can fit the particle spectra well. We show that the Tsallis distribution with thermodynamical description gives lower temperatures than the ones without it. The extra factormT(transverse mass) in the Tsallis distribution with thermodynamical description plays an important role in the discrepancies between the two types of Tsallis distribution. But for the heavy particles, the choice to usemTorET(transverse energy) in the Tsallis distribution becomes more crucial.

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