Freezeout properties of different light nuclei at the RHIC beam energy scan

Ajaz, Muhammad; Peng, Guang; Wang, Ruiqin; Ajaz, M.; Ismail, A. Haj

doi:10.1140/epjp/s13360-021-02089-1

“…We observed that both of them decrease with increasing pseudo-rapidity due to the large energy transfer in lower pseudo-rapidity intervals. The physics behind this is that larger energy transfer in the lower pseudo-rapidity bin results in higher degree of excitation of the system which results in larger and 10 , 38 – 41 and this indicates that the system in lower pseudo-rapidity intervals comes to equilibrium quickly. In addition we also observed that q (n) is increasing (decreasing) with the increase of rapidity.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, spectra are different for different particles in the range of 0 to 100 , which makes it difficult to explain how wide is the distribution range for different energies. However, one can discuss different ranges including very low, low, intermediate, high, and very high regions 5 – 10 . Generally, spectra are the combination of two main processes, soft and hard processes.…”

Section: Introductionmentioning

confidence: 99%

Pseudorapidity dependence of the bulk properties of hadronic medium in pp collisions at 7 TeV

Ajaz

¹

,

Ismail

²

,

Waqas

³

et al. 2022

Sci Rep

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The measured charged particle $$p_T$$ p T spectra in proton-proton collisions obtained by the CMS experiment at CERN is compared with the simulation results of EPOS–LHC and Pythia8.24 models at 7 TeV center-of-mass energy. The Pythia8.24 model describes the experimental data very well, particularly in the high $$p_T$$ p T region. The model also predicts the $$p_T$$ p T spectra for $$|$$ | $$\eta $$ η $$|$$ | < 2.4 at 0 $$\le $$ ≤ $$p_T$$ p T $$\le $$ ≤ 6 $$\text {GeV/}c$$ GeV/ c . The EPOS–LHC model underpredicts the $$p_T$$ p T spectra from 0.1 to 2 $$\text {GeV/}c$$ GeV/ c in all $$\eta $$ η bins for about 20% and the $$p_T$$ p T spectrum from 0.1 to 4.2 $$\text {GeV/}c$$ GeV/ c for $$|$$ | $$\eta $$ η $$|$$ | < 2.4 by about 15% while reasonably predicts well for $$p_T$$ p T > 4.2 $$\text {GeV/}c$$ GeV/ c within the experimental errors. Furthermore, to get information about collective properties of the hadronic matter, modified Hagedorn function with embedded transverse flow velocity and thermodynamically consistent Tsallis distribution functions are used to fit the experimental data and simulated results. The values of $$\chi ^2/ndf$$ χ 2 / n d f show that the functions fit the data and simulation results well. The parameter extracted by the functions: $$\beta _T$$ β T , $$T_0$$ T 0 , and $$T_{eff}$$ T eff decreases with increasing $$\eta $$ η . The decrease in $$\beta _T$$ β T with increasing $$\eta $$ η is due to the large energy deposition in lower rapidity bins producing rapid expansion due to large pressure gradient resulting quick expansion of the fireball. Similarly, large energy transfer in the lower pseudo-rapidity bin results in higher degree of excitation of the system which results larger values of $$T_0$$ T 0 and $$T_{eff}$$ T eff . The values of the fit constant $$N_0$$ N 0 increase with $$\eta $$ η where the values of $$N_0$$ N 0 extracted from Pythia8.24 are closer to the data than the EPOS–LHC model. The Pythia8.24 model has better prediction than the EPOS–LHC model which might be connected to its flow-like features and color re-connections resulting from different Parton interactions in the initial and final state.

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“…The present work is a continuation of our work published in [ 16 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ] using different statistical fit functions to extract parameters relevant to the collective properties of the hadronic medium.…”

Section: The Methods and Formalismmentioning

confidence: 94%

Analyses of pp, Cu–Cu, Au–Au and Pb–Pb Collisions by Tsallis-Pareto Type Function at RHIC and LHC Energies

Li

¹

,

Ajaz

²

,

Ajaz

³

et al. 2022

Entropy

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The parameters revealing the collective behavior of hadronic matter extracted from the transverse momentum spectra of π+, π−, K+, K−, p, p¯, Ks0, Λ, Λ¯, Ξ or Ξ−, Ξ¯+ and Ω or Ω¯+ or Ω+Ω¯ produced in the most central and most peripheral gold–gold (Au–Au), copper–copper (Cu–Cu) and lead–lead (Pb–Pb) collisions at 62.4 GeV, 200 GeV and 2760 GeV, respectively, are reported. In addition to studying the nucleus–nucleus (AA) collisions, we analyzed the particles mentioned above produced in pp collisions at the same center of mass energies (62.4 GeV, 200 GeV and 2760 GeV) to compare with the most peripheral AA collisions. We used the Tsallis–Pareto type function to extract the effective temperature from the transverse momentum spectra of the particles. The effective temperature is slightly larger in a central collision than in a peripheral collision and is mass-dependent. The mean transverse momentum and the multiplicity parameter (N0) are extracted and have the same result as the effective temperature. All three extracted parameters in pp collisions are closer to the peripheral AA collisions at the same center of mass energy, revealing that the extracted parameters have the same thermodynamic nature. Furthermore, we report that the mean transverse momentum in the Pb–Pb collision is larger than that of the Au–Au and Cu–Cu collisions. At the same time, the latter two are nearly equal, which shows their comparatively strong dependence on energy and weak dependence on the size of the system. The multiplicity parameter, N0 in central AA, depends on the interacting system’s size and is larger for the bigger system.

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“…One may also structure the three-component function from the invariant yield [Eq. (1)] directly, in which the three expressions are added directly and the parameters include the free parameters T 1 , T 2 and T 3 and the normalization constants V 1 , V 2 and V 3 . One has…”

Section: Two Analytic Functionsmentioning

confidence: 99%

Pseudorapidity dependence of the $p_T$ spectra of charged hadrons in $pp$ collisions at $\sqrt{s}$ = 0.9 and 2.36 TeV

Yang,

Ajaz,

Waqas

et al. 2022

Preprint

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We report the predictions of different Monte Carlo event generators including HIJING, Pythia, and QGSJETII in comparison with the experimental data measured by the CMS Collaboration at CERN in proton-proton (pp) collisions at center-of-mass energy √ s = 0.9 and 2.36 TeV. The CMS experimental transverse momentum (pT or p ⊥ ) spectra of charged hadrons were measured for pseudorapidity range 0 ≤ η ≤ 2.4 with bin width of η = 0.2 (for pT from 0.1 to 2 GeV/c) and a single bin of η for |η| < 2.4 (for pT from 0.1 to 4 GeV/c). Pythia reproduced the pT spectra with reasonable agreement for most of the pT range. It depicts better results in the case of the |η| < 2.4 than HIJING and QGSJETII which could reproduce the spectra in a limited pT range. Furthermore, to analyze the pT spectra of charged hadrons measured by the CMS Collaboration, we used a three-component function (structured from the Boltzmann distribution) and the q-dual function (from the q-dual statistics) to extract parameter values relevant for the study of bulk properties of hadronic matter at high energy. We have also applied the two analytic functions over the model predictions. The values extracted by the functions from the HIJING and Pythia models are closer to the experimental data than the QGSJETII model. Although the models could reproduce the pT spectra of all charged particles in some of the pT range but none of them could reproduce the distributions over the entire pT range and in all the pseudorapidity regions.

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Freezeout properties of different light nuclei at the RHIC beam energy scan

Cited by 19 publications

References 64 publications

Pseudorapidity dependence of the bulk properties of hadronic medium in pp collisions at 7 TeV

Pseudorapidity dependence of the bulk properties of hadronic medium in pp collisions at 7 TeV

Analyses of pp, Cu–Cu, Au–Au and Pb–Pb Collisions by Tsallis-Pareto Type Function at RHIC and LHC Energies

Pseudorapidity dependence of the $p_T$ spectra of charged hadrons in $pp$ collisions at $\sqrt{s}$ = 0.9 and 2.36 TeV

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