arXiv subjects

Junaid Tariq

Publications and source records attributed to Junaid Tariq.

6 recordsLinked to original sources

arXiv2024

Kinetic temperature and radial flow velocity estimation using identified hadrons and light (anti-)nuclei produced in relativistic heavy-ion collisions at RHIC and LHC

We report the investigation of the kinetic freeze-out properties of identified hadrons ($π^\pm$, $K^\pm$ and $p(\bar p)$) along with light (anti-)nuclei $d (\bar d)$, $t (\bar t)$ and ${}^{3}He$ in relativistic heavy-ion collisions at RHIC and LHC energies. A simultaneous fit is performed with the Blast-Wave (BW) model to the transverse momentum ({\ppt}) spectra of identified hadrons together with light (anti-)nuclei produced in $Au+Au$ collisions at {\sqrtsNN} = 7.7 -- 200 GeV at the RHIC and in $Pb+Pb$ collisions at $\sqrt{\mathrm{s}_{_{\mathrm{NN}}}}$ = 2.76 TeV at the LHC. The energy and centrality dependence of freeze-out parameters, i.e., kinetic freeze-out temperature ($T_{kin}$) and collective flow velocity $\langle β\rangle$ has been studied. It is observed that light (anti-)nuclei also participate in the collective expansion of the medium created in the collision when included in a common fit with the light hadrons. We observe a marginal rise in $T_{kin}$ and a slight decrease in $\langle β\rangle$ when compared to the values obtained from the fit to light hadrons. A similar $\langle β\rangle$ and significantly larger $T_{kin}$ is observed when a fit is performed to only protons and light (anti-)nuclei. Both, $T_{kin}$ and $\langle β\rangle$ show a weak energy dependence at most collision energies.

nucl-th↗

arXiv2024

Effect of hadronic cascade time on freeze-out properties of Identified Hadrons in Au+Au Collisions at $\sqrt{s_{NN}}$ = 7.7-39 GeV from AMPT Model

We report the transverse momentum $p_T$ spectra of identified hadrons ($π^\pm$, $K^\pm$ and $p(\bar p)$) in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7 - 39 GeV from A Multi Phase Transport Model with string melting effect (AMPT-SM). During this study, a new set of parameters are explored to study the effect of hadronic cascade by varying hadronic cascade time $t_{max}$ = 30 $f$m/$c$ and 0.4 $f$m/$c$. No significant effect of this change is observed in the $p_T$ spectra of light hadrons and the AMPT-SM model reasonably reproduces the experimental data. To investigate the kinetic freeze-out properties the blast wave fit is performed to the $p_T$ spectra and it is found that the blast wave model describes the AMPT-SM simulations well. We additionally observe that the kinetic freeze-out temperature ($T_{kin}$) increases from central to peripheral collisions, which is consistent with the argument of short-lived fireball in peripheral collisions. Whereas the transverse flow velocity, $<β_T>$ shows a decreasing trend from central to peripheral collisions indicating a more rapid expansion in the central collisions. Both, $T_{kin}$ and $<β_T>$ show a weak dependence on the collision energy at most energies. We also observe a strong anti-correlation between $T_{kin}$ and $<β_T>$. The extracted freeze-out parameters from the AMPT-SM simulations agree with the experimental data as opposed to earlier studies that reported some discrepancies. Whereas, no significant effect is found on the freeze-out parameters by varying the $t_{max}$. We also report the $p_T$ spectra of light hadrons and their freeze-out parameters by AMPT-SM simulations at $\sqrt{s_{NN}}$ = 14.5 GeV, where no experimental data is available for comparison. Overall, the set of parameters used in this study well describes the experimental data at BES energies.

hep-ph↗

arXiv2023

Study of Baryon number transport using model simulations in $pp$ collisions at LHC Energies

We report on the excitation function of anti-baryon to baryon ratios ($\overline{p}/p$, {\alam /\lam} and {\axi / \xim}) in $pp$ collisions at {\sqrts} = 0.9, 2.76, 7 TeV from DPMJET-III, Pythia~8, EPOS~1.99, and EPOS-LHC model simulations. To study the predictions of these models at {\sqrts} = 13.6 TeV. The anti-baryon to baryon ratios are extremely important for the study of baryon number transport mechanisms. These ratios help determine the carriers of the baryon number and in the extraction of baryon structure information. Even though all models show a good agreement between model simulations and data, the ratios extracted from DPMJET-III model closely describes data at all energies. It is observed that these ratios converge to unity for various model predictions. This convergence also indicates that the anti-baryon to baryon ratios follow the mass hierarchy, such that the hyperon specie containing more strange quarks ({\alam /\lam} and {\axi / \xim}) approaches unity faster than specie containing fewer strange quarks ($\overline{p}/p$). It is also observed that the $\overline{B}/B$ ratio approaches unity more rapidly with the increase in {\sqrts} energy. At lower energies we observe an excess production of baryons over anti-baryons. However, this effect vanishes at higher energies due to the baryon-anti-baryon pair production and the baryon-anti-baryon yield becomes equal. Using model simulations, we additionally compute the asymmetry, ($A\equiv\frac{N_{p}-N_{\bar{p}}}N_{p}+N_{\bar{p}}}$) for protons. The asymmetry shows a decreasing trend with increase in energy from 0.9 to 7 TeV for all energies. This asymmetry trend is confirmed by model predictions at {\sqrts} = 13.6 TeV which will help to put possible constraints on model calculations at {\sqrts} = 13.6 TeV once the Run-III data for LHC becomes available.

hep-ph↗

arXiv2023

Study of strange quark density fluctuations in Au+Au Collisions at $\sqrt{s_{NN}}$ = 7.7-200 GeV from AMPT Model

The strangeness production is an important observable to study the QCD phase diagram. The yield ratios of strange quark can be helpful to search for the QCD critical end point (CEP) and/or first-order phase transition. In this work, we studied the production of $K^{\pm}$, $Ξ^-(\barΞ^{+})$, $ϕ$ and $Λ(\bar Λ)$ in {\auau} collisions at {\sqrtsNN} = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV from A Multi-Phase Transport model with string melting version (AMPT-SM). We calculated the invariant yield of these strange hadrons using a different set of parameters compared to those reported in earlier studies and also by varying the hadronic cascade time ($t_{max}$) in the AMPT-SM model. We also calculated the yield ratios, $\mathcal{O}_{K^{\pm}-Ξ^{-}(\bar Ξ^{+})-ϕ-Λ(\bar Λ)}$ which are reported as sensitive to the strange quark density fluctuations and found that the AMPT-SM model fails to describe the non-monotonic trend observed by the experimental data. The negative particle ratio are found to be higher than the ratio of positive particles which is consistent with the experimental data. A significant effect is also seen on these ratios by varying the $t_{max}$. For a crossover transition between the Quark-Gluon Plasma (QGP) and hadronic matter, the double yield ratios considered in the present study based on AMPT-SM model do not show any non-monotonic behaviors and thus providing a baseline for the search of CEP, because there is no first-order or second-order phase transition in the AMPT model. The more realistic equation of state based dynamical modeling is still required for the heavy-ion collisions in order to extract the definite physics conclusion about the non-monotonic energy dependence behavior.

hep-ph↗

arXiv2022

Freeze-out Properties of Different Strange Hadrons from {\auau} Collisions at {\sqrtsNN}~= 54.4 GeV

We analyzed the transverse momentum {\ppt} spectra of different particle species containing strange quark {\ks}, {\lam (\alam)} and {\xim ({\axi})} in different centrality intervals at mid-rapidity ($y$) from {\auau} collisions at {\sqrtsNN}= 54.4 GeV. The {\ppt} spectra of these strange hadrons are investigated by Tsallis-like distribution. The Tsallis-like distribution satisfactorily fits the experimental data. The effective temperature, entropy based parameter $q$ and mean {\ppt} extracted from the Tsallis-like distribution function while the kinetic freeze-out temperature ($T_0$) and transverse flow velocity ($β_T$) are extracted by an alternative method. The effective temperature, entropy based parameter $q$ and mean {\ppt} are found to be strongly dependent on centrality. The effective temperature of multi-strange particle ({\xim ({\axi})}) is larger as compared to singly-strange particles {\lam (\alam)} and {\ks}. Furthermore, the extracted parameters from alternative approach decreases from central collisions to peripheral collisions, except the parameter $q$ which shows an opposite behaviour. A mass dependent kinetic freeze-out scenario is observed as the effective flow is larger for massive particles than the lighter one. Furthermore, the $T$, $β_T$ and mean {\ppt} ($\langle p_T \rangle$) shows decreasing trend as we go from central collisions to peripheral collisions. The entropy parameter $q$ increases from central to peripheral collisions.

hep-ph↗

arXiv2022

A Comprehensive Study of Energy Dependence of Particle Ratios in $pp$ Collisions from SPS to LHC Energies

A comprehensive study has been performed to estimate the kaon to pion ($K^\pm$/$π^\pm$) yield ratio and total kaon to total pion ($K$/$π$) yield ratio as a function of centre of mass energy in $pp$ collisions at different energies i.e., \sqrts~= 6.3, 17.3, 62.4, 200, 900 GeV, 2.76 TeV, 7 TeV, 13 TeV and 14 TeV using EPOS1.99, EPOS-LHC, HIJING, QGSJETII-03 and Sibyll2.3d model simulations. NA61/SHINE experiment reported that $K^+/π^+$ yield ratio exhibits rapid changes at the SPS energy range. A horn like structure appears in $K/π$ yield ratio as a function of collision energy. Significant presence of horn in $K^+$/$π^+$ and $K^-$/$π^-$ yield ratio is suggested by experimental data at lower energies, which is confirmed by HIJING and EPOS-LHC models. A smooth increase in $K/π$ yield ratio is also seen at higher energies. The model simulations predict similar increase in yield ratio with increasing energies. On the basis of previous available measurements, we also study model predictions of these yield ratios at \sqrts~= 13 and 14 TeV where no data is available. Almost all models suggest a saturation in the yield ratio within statistical fluctuations at these energies except EPOS1.99 and QGSJETII-03 which slightly over predict the yield ratio. These systematic comparisons are helpful to apply possible constraints on various hadronic event generators to significantly improve the predictions of Standard Model physics as well as for the understanding of underlying physics mechanisms in high energy collisions.

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