arXiv subjects

Satya Ranjan Nayak

Publications and source records attributed to Satya Ranjan Nayak.

8 recordsLinked to original sources

arXiv2026

Separating non-collective effects in d-Au collisions

In this work, we present the multiplicity and yield of charged hadrons and particle ratios in d-Au collisions at $\sqrt{s_{NN}}= 200$ GeV using the PYTHIA8/Angantyr. The model reproduces the multiplicity ($N_{ch}$) and pseudo-rapidity distribution reasonably well in minimum-biased d-Au collisions without assuming the formation of a thermalized medium. The invariant yield from Angantyr underpredicts the data in central collisions. We discussed the similarity between the nuclear modification factor $R_{AA}$ and data/MC from Angantyr and the possibility of using it as a model-dependent observable to check in-medium effects. The data/MC suggests that the central d-Au collisions exhibit signals like baryon enhancement, but no high $p_T$ suppression was found. The d-Au collisions have a much smaller invariant yield than the thermal model calculation for similar $N_{part}$.

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arXiv2026

Effects of Geometric configuration in relativistic isobaric collisions at $\sqrt{s_{NN}}=200$ GeV

In this work, we present a study on the effects of nuclear deformation ($β_2$,$β_3$) and surface diffuseness ($a$) on the charged hadron multiplicity ($N_{\mathrm{ch}}$) and elliptic flow ($v_2$), obtained in symmetric isobaric collisions of ${}^{96}_{44}\mathrm{Ru} + {}^{96}_{44}\mathrm{Ru}$ and ${}^{96}_{40}\mathrm{Zr} + {}^{96}_{40}\mathrm{Zr}$. The two extreme configurations (tip-tip and body-body) were used to determine the correlation between the final state observables and initial geometry using the HYDJET++ model. The octupole deformation parameter ($β_3$) enhances $N_{\mathrm{ch}}$ in central tip-tip Zr+Zr collisions and suppresses it in peripheral ones. In mid-central to peripheral body-body Zr+Zr collisions, $β_3$ leads to a reduction in charged hadron production. Surface-diffuseness ($a$), along with quadrapole deformation ($β_2$), also shows a significant impact on multiplicity and elliptic flow. The octupole deformation enhances elliptic flow in Zr's body-body collisions. Results are compared with the STAR blind-analysis data where available.

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arXiv2026

Physics-informed neural network (PINN) modeling of charged particle multiplicity using the two-component framework in heavy-ion collisions: A comparison with data-driven neural networks

In this study, we employ a conventional deep neural network (NN) framework integrated with physics-based constraints to predict charged hadron multiplicity ($N_{\text{ch}}$) in heavy-ion collisions. The goal is to assess the performance of a purely data-driven deep neural network in comparison to a physics-informed neural network (PINN). To accomplish this, we have taken data generated from the HYDJET++ model for testing and training purposes. We train our neural network frameworks using the data of one million individual $^{96}_{40}\text{Zr}+^{96}_{40}\text{Zr}$ collision events. Our PINN model successfully extracts the hard-scattering fraction ($x$) by learning its underlying relation from the event data. For further testing and comparison with the conventional NN, we take data of $^{96}_{44}\text{Ru}+^{96}_{44}\text{Ru}$ (isobar of Zr) and $^{197}_{79}\text{Au}+^{197}_{79}\text{Au}$ collisions using the same simulation model. We found that the NN model needs more time to train with physics. However, once trained, the PINN model is capable of accurately predicting data that it has not encountered during training, such as Au+Au collision results. Especially in a region of sparse data corresponding to high $N_{\text{ch}}$ in our study, PINN has a clear advantage over a simple NN.

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arXiv2026

Two-particle cumulant distribution: a simulation study of higher moments

In this work, we have shown the two-particle correlations of charged hadrons in d-Au collisions at 200 GeV in PYTHIA8/Angantyr simulations. These correlations were studied at different multiplicities and pseudorapidity intervals. The two-particle correlations arise due to color reconnections, resonance decays, jet correlations, and hadronic rescattering. These correlations are inversely proportional to multiplicity but remain unaffected for larger pseudorapidity windows. We treated these correlations as distributions and calculated their skewness and kurtosis. The non-flow distributions deviate greatly from a Gaussian distribution and have high skewness and kurtosis. The ``true" elliptic flow distributions resemble Gaussian distributions; they have significantly lower skewness and kurtosis. We suggest that if the two-particle cumulant flow is treated as an event-by-event distribution, its skewness and kurtosis can be instrumental in distinguishing true flow and non-flow.

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arXiv2026

Statistical properties of non-flow correlations in pp and heavy-ion collisions at RHIC energies

In this work, we have studied the two-particle cumulant in pp, d-Au, and Au-Au collisions. The two-particle cumulant was treated as an event-by-event distribution, and its skewness and kurtosis were analyzed. The non-flow correlations, like jets and decays, constantly produced a skewed distribution, regardless of the model used. On the contrary, HYDJET++ produced a smooth Gaussian distribution at higher $η$ windows in fixed impact parameter collisions. The skewness increased consistently for higher $η$ windows in all non-QGP models like PYTHIA, PHOJET, QGSJET, and DPMJET. The kurtosis of the distribution also increased with $η$ windows in non-QGP models. The skewness and kurtosis of the distributions produced by HYDJET++ decreased with $Δη$ and eventually reached zero at higher $Δη$.

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arXiv2025

Study of Particle Production in Au+Au Collisions at $\sqrt{s_{NN}} =$ 11.5-200 GeV Using HYDJET++ Framework

Using the HYDJET++ model, we study the production of multi-strange particles($ϕ$ and $Ω$) in Au+Au collisions at $\sqrt{s_{NN}} =$ 11.5, 19.6, 27, 39, and 200 GeV as functions of transverse momentum and centrality. The model calculations employ earlier freeze-out hypersurfaces for multi-strange particle production and are compared with STAR experimental data. Results indicate that the HYDJET++ model demonstrates a better agreement with experimental data for multi-strange particles at higher energies, particularly in relation to early thermal freeze-out. Meanwhile, the default version performs more accurately for lighter, non-strange particles at the same energy scales. We also analyze identified particle and mixed particle ratios, providing insights into strangeness enhancement. The results provide additional constraints on parton energy loss models, contributing to a more precise determination of the transport properties of hot and dense QCD matter.

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arXiv2025

Beam energy dependence of transverse momentum distribution and elliptic flow in Au-Au collisions using HYDJET++ model

In this work, we present the particle ratios, transverse momentum spectra, and elliptic flow ($v_2$) of $π^\pm,k^\pm,$ $p$, and $\bar{p}$ in Au-Au collisions at $\sqrt{s_{NN}}=$ 62.4, 39.0, 27.0, 19.6 and 11.5 GeV using HYDJET++ model. The particle ratios match the experimental data that validates the Cleymans-Reidlich parameterization of freeze-out parameters at lower beam energies under the HYDJET++ framework. The lower collision energies produce a system of high baryon chemical potential ($μ_B$) and have a lower inelastic cross section. The interplay between these effects affects the overall shape of the $p_T$ spectra. The HYDJET++ model calculations for $p_T$ spectra agree well with the available experimental data. The invariant yield ratio of central and peripheral collisions is independent of beam energy. The elliptic flow is calculated based on the scaling between initial and final azimuthal spatial anisotropy ($k$). This interpretation of $v_2$ successfully describes the experimental data for all the collision energies studied in this work. The positive correlation of $k$ with beam energy leads to a small $v_2$ at lower collision energies. The hadrons containing strange quarks tend to have smaller values of $k$ than the non-strange hadrons.

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arXiv2025

A background for thermal photons in heavy ion collisions

In this work, we present the transverse momentum spectra of prompt and decay photons in Au-Au collisions for $\sqrt{s_{NN}}=$ 200 GeV, 62.4 GeV, 39 GeV, and 27 GeV. The major sources of the photons in Angantyr include hard processes, Parton showers, and resonance decay. The multiparton interactions and hadronic rescatterings significantly increase the photon yield. The model shows a good match with the available experimental data at high $p_T$. The difference in yield at low $p_T $ suggests that Quark Gluon Plasma of $T_{eff}$ = 0.167 GeV/c in central Au-Au collision at 200 GeV is formed, the new effective temperature is less than the ones extracted without removing background photons. At low $p_T$ the decay photon spectra scales with $(\frac{dN_{ch}}{dη})^{1.25}$, the scaling is independent of collision energy and system size. The scaling no longer holds at high $p_T$ and the spectra become beam energy dependent. The scaled $p_T$ spectra of p-p and d-Au collisions show an opposite trend at high $p_T$, their scaled yield is greater than the Au-Au collision at the same energy.

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