arXiv subjects

Murad Badshah

Publications and source records attributed to Murad Badshah.

10 recordsLinked to original sources

arXiv2026

Harmonic-dependent geometry-to-flow transfer in AMPT Ru+Ru and Zr+Zr isobar collisions

We present a fixed-$N_{\rm part}$ study of geometry-to-flow transfer in string-melting AMPT simulations of $^{96}{\rm Ru}+^{96}{\rm Ru}$ and $^{96}{\rm Zr}+^{96}{\rm Zr}$ collisions at $\sqrt{s_{NN}}=200$ GeV. Four nuclear configurations are considered: deformation-only Ru+Ru, deformation-only Zr+Zr, deformation plus neutron skin Ru+Ru and deformation plus neutron skin Zr+Zr. The AMPT/HIJING initialization is modified to include deformed Woods--Saxon densities and, when enabled, separate proton and neutron Woods--Saxon radii and diffuseness parameters (neutron skin effect). We introduce an eccentricity-normalized isobar response double ratio, $D_n=(v_n^{\rm Ru}/v_n^{\rm Zr})/(\varepsilon_n^{\rm Ru}/\varepsilon_n^{\rm Zr})$, evaluated in common participant-number intervals. This observable eliminates the initial-geometry eccentricity ratio, and investigates whether the final-state flow ratio is fully determined by the initial-geometry ratio. We find that the elliptic double ratio is nearly unity, and the triangular double ratio is consistently greater than unity for the two deformation-only and deformation-plus-skin configurations. The positive $D_3-1$ pattern is maintained when varying the $N_{\rm part}$ binning, peripheral-bin treatment, flow $p_T$ range and rapidity/pseudorapidity acceptance. The result identifies a harmonic-dependent AMPT response: Ru/Zr elliptic flow follows leading eccentricity scaling to high accuracy, whereas triangular flow retains a residual response component after the triangularity ratio is divided out.

nucl-th↗

arXiv2026

Comparing EPOS-4, EPOS-LHC, and SMASH for identified-hadron observables in the NICA energy range

We present a systematic simulation study of identified hadron production in minimum bias Au+Au collisions at sqrt(sNN) = 6, 7, and 8 GeV. The event samples were generated with three modern frameworks based on different microscopic pictures: EPOS-LHC, EPOS-4, and the purely hadronic transport model SMASH. We compare observables that probe baryon stopping, transverse dynamics, hadron formation, and strangeness production: rapidity densities dN/dy, transverse momentum spectra dN/dpT, two dimensional pT-y distributions, v2/nq versus pT/nq, and the yield ratios pi-/pi+, K-/K+, pbar/p, K+/pi+, K-/pi-, p/pi+, and Lambda/pi+. For charged and neutral pions, the three models give broadly similar yields and spectral shapes in both dN/dy and dN/dpT. At these energies, resonance decays and isospin constraints reduce the sensitivity to early stage dynamics. In contrast, strange mesons and baryons remain strongly model dependent. EPOS-4 gives the largest midrapidity K+ and Lambda yields and the hardest kaon and strange baryon pT spectra. EPOS-LHC is generally intermediate, while SMASH gives lower strange hadron production. The two dimensional pT-y maps show that the EPOS models populate higher pT over a broader rapidity range. For NCQ scaled elliptic flow, the best approximate scaling is seen in EPOS-LHC, while SMASH and EPOS-4 show only partial scaling. This suggests that EPOS-LHC carries a more coherent partonic anisotropy to the hadronic stage in this energy range. Overall, the model separation grows from 6 to 8 GeV. The clearest discriminators in the NICA domain are intermediate pT baryon to meson ratios, Lambda/pi+, the rapidity dependence of pT, the pT dependence of K-/K+, and NCQ scaled v2.

hep-ph↗

arXiv2026

Collectivity Signatures in High-Multiplicity pp Collisions from Hybrid Hydro+Tsallis Modeling of Pion Spectra

The transverse momentum (pT) distributions up to pT = 20 GeV/c for pions produced in the ten different multiplicity classes (MCs) of symmetric pp collisions at sqrt(s) = 7 TeV have been investigated. Two distinct models, the Tsallis-Pareto type function (model) and the combined BGBW model and Tsallis-Pareto type model have been employed to fit the pT distributions via the minimum chi-square method. The combined Hydro+Tsallis model is more reliably describing the pT spectra than the Tsallis-Pareto model. The Tsallis temperature (T), non-extensivity parameter (q), normalization constant (N0), Kinetic freeze-out temperature (T0), transverse flow velocity (betaT), and (mean pT) have been extracted through the fitting procedure via the employed models. The Tsallis-Pareto model gives T, q, N0 and mean pT while Hydro+Tsallis model gives T0, betaT, T, q, N0 and mean pT. Incorporating the values of the extracted T and q the thermodynamic quantities and response functions, including energy density (epsilon), particle density (n), entropy density (s), pressure (P), specific heat at constant volume (CV), squared speed of sound (cs2), mean free path (lambda), Knudsen number (Kn), isothermal compressibility (kappaT), and expansion coefficient (alpha) have been calculated at the freeze-out stage. It has been observed that T, betaT, mean pT, N0, epsilon, n, s, P, CV, cs2, and alpha increase with increasing(decreasing) the charged particles multiplicity density dNch/deta(MCs). While T0, q, lambda, Kn, and kappaT decrease with increasing(decreasing) dNch/deta(MCs). These systematic variations in the trends of parameters might suggest the gradual transition towards collectivity and thermal equilibration in the high multiplicity pp events, possibly signalling enhanced collective dynamics and partial thermalization in small collision systems.

hep-ph↗

arXiv2026

Exploring Thermalization and Multi-Freeze-Out Effects in Pb-Pb collisions Based on Tsallis pT Distributions

This study investigates transverse-momentum (pT) distributions of pi-, pi+, K-, K+, p, pbar, K0s, and Lambda in several centrality classes of Pb-Pb collisions at sqrt(sNN) = 2.76 TeV. The measured spectra are analyzed with the Tsallis non-extensive distribution, from which the effective temperature T, non-extensive parameter q, and the mean transverse momentum mean_pT are extracted for each particle species and centrality interval. To disentangle thermal and collective effects, the mean kinetic freeze-out temperature T0 is obtained from the intercept of the T-versus-mass relation, while the average transverse flow velocity betaT is extracted from the slope of mean_pT versus the mean moving mass for pions, kaons, and protons. The results show that T increases and q decreases with increasing centrality, indicating a hotter and more equilibrated system in central collisions. A clear mass dependence of T supports a multi-freeze-out scenario, with heavier particles decoupling earlier. Both T0 and betaT rise from peripheral to mid-central collisions before saturating toward central events, which may suggest the onset of collective behavior or changes in freeze-out dynamics. These observations provide new insights into the thermal and dynamical properties of the medium created in heavy-ion collisions at the LHC.

hep-ph↗

arXiv2024

Evolution of Effective Temperature, Kinetic Freeze-out Temperature and transverse flow velocity in pp Collision

This article focuses on the study of strange hadrons at 0.2 TeV centre of mass energy, recorded by STAR at RHIC, and at 0.9 TeV, 5.02 TeV and 7 TeV, recorded by CMS at LHC, in pp collision in the rapidity range from 0 to 2. The transverse momentum distributions of these strange particles have been processed using two statistical models, the Tsallis and the modified Hagedorn model. Both models fit the experimental data well. We extracted different freezeout parameters from the fit procedure using the abovementioned functions. We found that with increasing the collision energy, the effective temperature (T), in the case of the Tsallis model, and kinetic/thermal freeze-out temperature (T0) and transverse flow velocity, in the case of the modified Hagedorn model, increase because of greater energy transfer among the participants at higher colliding energies. Both T and T0 are observed to increase with the increase in the rest masses of the outgoing particles revealing the multi-freeze-out scenario. Furthermore, the multiplicity parameter (N0) decreases with the increase in the particle mass, confirming the mass differential freeze-out scenario. An inverse relationship between the non-extensivity parameter (q) and the masses of the produced particles has been noticed. Similarly, an inverse correlation between q and T has been found. For lighter particles, smaller T and greater q mean that they decouple from the system later and attain equilibrium slowly compared to heavier ones. In addition, a positive correlation between transverse flow velocity and T0 is noticed, which agrees with the literature.

hep-ph↗

arXiv2024

Systematic analysis of the pp collisions at LHC energies with Tsallis function

This work focuses on the study of identified hadrons and strange hadrons, recorded by CMS, and light nuclei and their anti-nuclei, recorded by ALICE, at 0.9 TeV, 2.76 TeV, 7 TeV and 13 TeV centre of mass energies in pp collision at mid rapidities. The transverse momentum distributions of these particles are analyzed using the Tsallis model, which fits the experimental data very well. Several important parameters for studying the characteristics of the medium produced during such collisions are extracted. The effective temperature (T) increases monotonically with increasing particle mass and also with increasing collision energy. The non-extensivity parameter (q) decreases with the mass of the particle. For heavier particles, greater T and smaller q mean that they decouple early from the system and attain equilibrium quickly compared to lighter ones. Furthermore, with an increase in collision energy, the multiplicity parameter N0 increases.

hep-ph↗

arXiv2024

Investigating the Bulk Properties of Charged Particles in Different $η$ Bins Using a Modified Tsallis Model

This paper presents a comprehensive analysis of the double-differential $p_T$ distributions of charged particles in twelve distinct pseudorapidity regions of equal width in $pp$ collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV. Utilizing the modified Tsallis function with mean transverse flow velocity, our study demonstrates a very good agreement between experimental data and the model employed. The fit quality is consistently high across all $p_T$ ranges, as assessed by Data/Fit panels accompanying each plot. Extracted parameters, including kinetic freeze-out temperature ($T_0$), transverse flow velocity ($β_T$), non-extensivity parameter ($q$) and mean transverse momentum $\langle p_T \rangle$ dependencies are shown on pseudorapidity ($η$) and collision energy ($\sqrt{s}$). $T_0$, $β_T$ and $\langle p_T \rangle$ exhibit a decreasing trend with increasing $η$ due to lower in energy transfer along high $η$ regions, while they show a heightened sensitivity to $\sqrt{s}$. $q$ increases with $η$, indicating a closer thermal equilibrium in mid-$η$ particles. The paper also explores correlations among these parameters, emphasizing relationships between $T_0$, $β_T$, $q$ and $\langle p_T \rangle$. Our study provides valuable insights into the thermal and dynamic characteristics of high-energy proton-proton collisions, contributing to the broader understanding of the bulk properties of nuclear matter produced in these interactions.

hep-ph↗

arXiv2024

Thermodynamic Signatures and Phase Transitions in High-Energy Au-Au Collisions

In this study, we systematically investigate the dynamics of various hadrons namely $ π^+ $, $ π^- $, $ K^+ $, $ K^- $, $ p $, $ \bar{p} $, $ Λ$, $ \barΛ $, $ Ξ^- $ and $ \barΞ^+ $ produced in central Au-Au collisions. We analyze data of AGS and RHIC, which span a broad range of collision energies, ranging from $ \sqrt{s_{NN}}$ = 1.9 to 200 GeV. To analyze the transverse momentum ($ p_T $) and transverse mass ($ m_T $) distributions, we employ a two-component standard distribution function, achieving a very good representation of the experimental data across these energy regimes. We extract key thermodynamic parameters, including the effective temperature $ T $, the mean transverse momentum $ \langle p_T \rangle $, and the initial temperature $ T_i $, and analyze their dependence on the values of collision energy and particle mass. Our findings reveal a distinct transition behaviour around $ \sqrt{s_{NN}} = 19.6 $ GeV. Below $ \sqrt{s_{NN}} = 19.6 $ GeV, the values of $ T $, $ \langle p_T \rangle $, and $ T_i $ increase monotonically for all hadrons due to higher energy transfer into the system. Above this energy threshold, these extracted parameters plateau, suggesting that the additional energy is utilized as latent heat for phase transition rather than increasing the system's temperature. These observations delineate two distinct regions: a hadron-dominated region at lower energies and a parton-dominated region at higher energies, each potentially indicative of different phases of matter, with the latter possibly signalling the onset of a Quark-Gluon Plasma (QGP). The study thus provides critical insights into the complex interplay of thermodynamics, phase transitions, and particle interactions in high-energy Au-Au collisions.

hep-ph↗

arXiv2024

Multiplicity dependence of the freezeout parameters in high energy hadron-hadron collisions

We examined the transverse momentum spectra of various identified particles, across different multiplicity classes in proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 7 TeV. Utilizing the Tsallis and Hagedorn models, parameters relevant to the bulk properties of nuclear matter were extracted. Both models exhibit good agreement with experimental data. In our analyses, we observed a consistent decrease in the effective temperature for the Tsallis model and the kinetic or thermal freeze-out temperature for the Hagedorn model, as we transition from higher multiplicity (class-I) to lower multiplicity (class-X). Additionally, the transverse flow velocity experiences a decline from class-I to class-X. The normalization constant which represents the multiplicity of produced particles is observed to decrease as we move towards higher multiplicity classes. While the effective and kinetic freeze-out temperatures, as well as the transverse flow velocity, show a mild dependency on multiplicity for lighter particles, this relationship becomes more pronounced for heavier particles. Various particle species are observed to undergo decoupling from the fireball at distinct temperatures: lighter particles exhibit lower temperatures, while heavier ones show higher temperatures, thereby supporting the concept of multiple freeze-out scenarios. Moreover, we identified a positive correlation between the kinetic freeze-out temperature and transverse flow velocity, a scenario where particles experience stronger collective motion at higher freeze-out temperature. The reason for this positive correlation is that as the multiplicity increases, more energy is transferred into the system. This heightened energy causes greater excitation and pressure within the system, leading to a quick expansion.

hep-ph↗

arXiv2020

Constraints on $H^\pm$ parameter space in 2HDM at $\sqrt{s}=$ 8 TeV and $\sqrt{s}=$ 13 TeV

This paper reflects the heavy Higgs scenario where the mass of charged Higgs is equal to or greater than 200 GeV. The CMS observed and expected values of upper limits on the product $σ_H^\pm BR(H^\pm \rightarrow tb^\mp)$, assuming $H^\pm \rightarrow tb^\mp=1$, both at 8 TeV (at integrated luminosity of 19.7 $fb^{-1}$ ) and 13 TeV (at integrated luminosity of 35.9 $fb^{-1}$ ) c.m energies are used. By comparing these expected and observed upper limits with computational values , we find out the expected and observed exclusion regions of charged Higgs parameter space ($ m_H^\pm - tanβ$ space ) in 2HDM both at $\sqrt{s}=$8 and $\sqrt{s}=$ 13 TeV. We compare the expected and observed exclusion regions and observe that exclusion regions made by observed upper limits are always greater than the exclusion made by expected upper limits both at 8 and 13 TeV c.m energies. Only in the mass range from 200 GeV to 220 GeV the expected exclusion region is greater than the observed one only at $\sqrt{s}=$13 TeV. We also equate the exclusion regions at these two different center of mass energies and find that the expected exclusion region and observed exclusion region at $\sqrt{s}=$13 TeV are always greater than the expected exclusion region and observed exclusion region at $\sqrt{S}=$8 TeV respectively.

hep-ph↗