arXiv subjects

Salman Khurshid Malik

Publications and source records attributed to Salman Khurshid Malik.

6 recordsLinked to original sources

arXiv2026

Scaling of soft QGP signatures in relativistic lead, xenon and oxygen collisions in EPOS4

The collective expansion and hydrodynamic evolution in heavy-ion collisions is well-established. However, whether femtometer-scale droplets of QGP are produced in small systems at high energies remains a fundamental open question. Analysis of Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, Xe$-$Xe at $\sqrt{s_{\mathrm{NN}}}$ = 5.44 TeV and O$-$O collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.36 TeV using EPOS4 is reported to make predictions and postdictions. The results are compared with ALICE data for Pb$-$Pb and Xe$-$Xe collisions. Charged particle multiplicity (d$N_{\mathrm{ch}}$/d$η$), transverse-momentum ($p_{\mathrm{T}}$) spectra for pions ($π^{\pm}$), kaons ($K^{\pm}$), and protons ($\text{p}(\overline{\text{p}})$) are studied. The inclusion of hadronic afterburner, UrQMD (Ultra-relativistic Quantum Molecular Dynamics) is found to be necessary to correctly describe baryon yields. $p_{\mathrm{T}}$-fluctuations are also studied via normalized $p_{\mathrm{T}}$ correlator, $\sqrt{\langle \langle Δp_{\mathrm{T},i}Δp_{\mathrm{T},j} \rangle \rangle}\mathrm{/} \langle \langle p_{\mathrm{T}} \rangle \rangle$. Lastly, anisotropic flow harmonics ($v_{\mathrm{2}} \{2\}$, $v_{\mathrm{3}} \{2\}$) are computed as a function of $p_{\mathrm{T}}$ and centrality. Since EPOS4 has not been extensively studied for flow observables, this study thereby provides a non-trivial assessment of its collective dynamics. The results are compared with experiment wherever data is available. Taken together, this study provides a unified description of soft observables from Pb$-$Pb through Xe$-$Xe down to O$-$O and offer quantitative guidance on how such collisions may inform of the properties of the QGP.

hep-ph↗

arXiv2026

Topological analysis of scale-invariant spatial fluctuations in ultrarelativistic heavy-ion collisions

The QGP-to-hadronic matter phase transition and QCD critical point in heavy-ion collisions can be identified by studying spatial fluctuations among final-state particles using intermittency analysis. First CMC-based intermittency analysis in the two-dimensional angular ($η$, $φ$) phase space, using EPOS as the background model is presented. Critical fluctuation signals are extremely weak, constituting only a few percent of the total event sample and are severely diluted by the overwhelming non-critical background, rendering traditional intermittency analyses insufficient for reliable signal extraction. To extract the weak critical signal, we employ a two-stage topological machine learning framework combining Topological Data Analysis (TDA) with deep learning. In the first stage, particle events are represented as two-dimensional point clouds and a Delaunay-based sub-level set filtration is constructed to extract Betti curves as multiscale topological invariants, corrected for multiplicity bias via azimuthal randomisation and classified by two complementary architectures, a TopoPointNet (TPN) and Boosted Decision Trees (BDT). Since event-level classification alone is insufficient to restore the critical scaling, a second stage applies a particle-level density filter, explicitly stripping away the diffuse thermal background and isolating the densely packed critical clusters. The two stage pipeline successfully restores the power-law scaling of the normalized factorial moments, enabling accurate recovery of the intermittency index in ($η$, $φ$) space and establishing topological machine learning as a robust data driven tool for probing the QCD critical point and the phase structure of strongly interacting matter in heavy-ion collisions at LHC energies.

hep-ph↗

arXiv2026

Intermittency and fractal behaviour of charged particles in EPOS4 and PYTHIA8 generated events at LHC energies

Large number density fluctuations of the charged particles produced in heavy-ion collisions are a promising signature for exploring the QCD phase transition and critical point in the nuclear matter phase diagram. Intermittency methodology is used to probe the fractal and scale invariant nature of these fluctuations. Intermittency is the phenomenon of power-law growth of the normalized factorial moments ($F_{\rm{q}}$) of the number density distributions over decreasing bin size. The charged particles generated in the midrapidity region using PYTHIA8 and EPOS4 (UrQMD ON/OFF) for Pb--Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV are studied. Scaling behaviour of $F_{\rm{q}}$ are studied as a function of phase space partitioning and second order moments to quantify the particle production nature within the default constraints of the two models. The scaling exponent related to the phase transition and parameters connected to fractal nature obtained for both these models show the absence of fluctuations of critical nature and multifractal behaviour.

hep-ex↗

arXiv2023

Normalized factorial moments of spatial distributions of particles in high multiplicity events: A Toy model study

In ultra-relativistic heavy-ion collisions a strongly interacting complex system of quarks and gluons is formed. The nature of the system so created and the mechanism of multi-particle production in these collisions may be revealed by studying the normalized factorial moments ($F_{\rm{q}}$) as function of various parameters. The resilience of $F_{\rm{q}}$ moments studied using Toy model events shows that these are sensitive to the presence of dynamical fluctuations in the system and are robust against the uniform efficiencies in the data measurements. Results of this study serve as a suitable reference baseline for the experimental and simulation studies.

hep-ph↗

arXiv2022

Intermittency analysis of charged hadrons generated in Pb-Pb collisions at $\sqrt{s_{NN}}$= 2.76 TeV and 5.02 TeV using PYTHIA8/Angantyr

Local density fluctuations are expected to scale as a universal power-law when the system approaches critical point. Such power-law fluctuations are studied within the framework of intermittency through the measurement of normalized factorial moments in ($η$, $ϕ$) phase space. Observations and results from the intermittency analysis performed for charged particles in Pb-Pb collisions using PYTHIA8/Angantyr at 2.76 TeV and 5.02 TeV are reported. We observe no scaling behaviour in the particle generation for any of the centrality studied in narrow p$_T$ bins. The scaling exponent $ν$ shows no dependence on the centrality ranges.

nucl-ex↗

arXiv2020

Intermittency study of charged particles generated in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}\text{= 2.76 TeV}$ using EPOS3

Charged particle multiplicity fluctuations in Pb-Pb collisions are studied for the central events generated using EPOS3 (hydro and hydro+cascade) at $\sqrt{s_{\mathrm{NN}}}\text{ = 2.76 TeV}$. Intermittency analysis is performed in the mid-rapidity region in two-dimensional ($η$, $ϕ$) phase space within the narrow transverse momentum ($p_\rm{T}$) bins in the low $p_\rm{T}$~region ($p_\rm{T}~\leq~1.0~GeV/\textit{c}$). Power-law scaling of the normalized factorial moments with the number of bins is not observed to be significant in any of the $p_\rm{T}$-bin. Scaling exponent $ν$, deduced for a few $p_\rm{T}$ bins is greater than that of the value 1.304, predicted for the second order phase-transition by the Ginzburg-Landau theory. The link in the notions of fractality is also studied. Fractal dimensions, $D_{q}$ are observed to decrease with the order of the moment $q$ suggesting the multifractal nature of the particle generation in EPOS3.

hep-ex↗