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Ankhi Roy

Publications and source records attributed to Ankhi Roy.

17 recordsLinked to original sources
arXiv2026

Centrality Dependence of the Balance Functions for Identified Particles in Pb--Pb Collisions Using Pythia + Angantyr

In this paper, we study the balance functions for pions, kaons, and protons in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 2.76$ TeV using the PYTHIA 8.3 + Angantyr model. The balance function is evaluated through two-particle azimuthal angular correlations $(\Delta \phi, \Delta \eta)$ between particle and antiparticle. Correlations are constructed for $\pi\pi$, $KK$, and $pp$, and their dependence on collision centrality is investigated. The results indicate that the balance function for pions is narrower compared to kaons and protons. Notably, the pion balance function width decreases from peripheral to central collisions, while the widths for kaons and protons remain nearly unchanged. For the Monash 2013 tune used in this study, PYTHIA 8.3 + Angantyr describes peripheral collisions reasonably well but does not quantitatively reproduce central Pb--Pb data. This suggests that an improved description of central Pb--Pb collisions may require a dedicated heavy-ion tuning of the Angantyr framework. We further explore the influence of resonance decays and collective effects by incorporating multi-parton interactions and color reconnection into the analysis. Owing to resonance effects and Bose--Einstein correlations, a dip at $\Delta \eta = 0$ and $\Delta \phi = 0$ is observed for pions and kaons.

hep-ph↗
arXiv2024

An Impact of Parton Distribution Functions on Open Heavy Flavor Azimuthal Angular Correlations in Pb-Pb Collisions at $\sqrt{s_{NN}}$ = 5.5 TeV

In this paper, we investigate the impact of modern free parton distribution functions and nuclear parton distribution functions on the azimuthal angular correlation of open heavy flavor hadrons in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.5 TeV using PYTHIA8 + Angantyr model. The method involves a transverse momentum ($p_{\rm{T}}$) differential assessment of azimuthal angular correlations between prompt $\rm{D^0-\bar{D}^0}$ and $\rm{B-\bar{B}}$. By analyzing the $p_{\rm{T}}$-dependent behavior of these correlations, we probe the interplay between different production mechanisms and assess the impact of parton distribution functions on heavy-flavor hadron production dynamics. Our results indicate that nuclear parton distribution functions significantly modify both near-side and away-side peaks of the azimuthal correlation distribution compared to the default PYTHIA8 baseline, particularly at low $p_{\rm{T}}$. The near-side double-peak structure suggests contributions from next-to-leading order (NLO) processes, such as gluon splitting, and its presence is strongly correlated with the number of hard multi-partonic interactions. Additionally, by quantitatively comparing the change in correlation widths across various PDF settings, we comment on the role of nuclear parton distribution functions in heavy-quark thermalization in heavy-ion collisions. This comprehensive study of azimuthal correlations enhances our understanding of initial-state conditions and heavy-flavor production dynamics in nuclear collisions.

hep-ex↗
arXiv2024

Probing coalescence of light nuclei via femtoscopy and azimuthal anisotropies

The production mechanism of light nuclei in heavy-ion collisions is vital to understanding the intricate details of nucleon-nucleon interactions. The coalescence of nucleons is a well-known mechanism that attempts to explain the production mechanism of these light clusters. This work investigates the formation mechanism of these nucleon clusters with a combination of coalescence and femtoscopy of nucleons and nuclei. It is achieved by appending a coalescence and correlation afterburner (\texttt{CRAB}) to the \texttt{SMASH} transport model. To have a proper view of the anisotropy of light nuclei clusters, a mean-field approach to \texttt{SMASH} is applied. The anisotropic coefficients of various light nuclei clusters are calculated and compared to experimental measurements. To incorporate hydrodynamics into the picture, the anisotropic measurements are completed in a hybrid \texttt{SMASH}+\texttt{vHLLE} mode. In both approaches, the femtoscopy of nucleons and light nuclei is performed, reported with CRAB, and compared to the latest experimental measurements. An insight into cluster formation time is drawn by extracting the emission source size with the Lednický-Lyuboshits (LL) model.

nucl-th↗
arXiv2024

Searching for enhancement in coalescence of in-jet (anti-)deuterons in proton-proton collisions

Recent measurements from ALICE report that $``$in-jet'' nucleons carry a higher probability of forming a deuteron via coalescence than the nucleons from the underlying event (UE). This study makes use of an event shape classifier to separate the $``$in-jet'' deuterons and the deuterons in the UE produced in high multiplicity proton-proton collisions at $\sqrt{s} = 13$ TeV. Event shape variables such as transverse spherocity allow the categorization of hard and soft components of an event, which can be divided into two respective classes; $``$jetty'' and $``$isotropic''. The $``$jetty'' deuterons minus the contribution of the deuterons from the $``$isotropic'' event are taken as $``$in-jet'' deuterons, and the coalescence mechanism is tested. The coalescence is performed with a Wigner function formalism, augmented as an afterburner to \textsc{pythia}8. The possible enhancement of the coalescence probability of $``$in-jet'' deuterons is investigated by calculating the coalescence parameter ($B_{2}$) in different spherocity classes in high-multiplicity $pp$ collisions.

hep-ph↗
arXiv2023

Exploring light nuclei production at RHIC and LHC energies with A Multi-Phase Transport model and a coalescence afterburner

In heavy-ion collisions, understanding how light nuclei species are produced can provide insight into the nature of hadronic interactions in extreme conditions. It can also shed light on understanding the matter-antimatter asymmetry and dark matter searches in astrophysical processes. To investigate the production mechanism of light nuclei such as deuteron, triton, and helium-3, we use a naive coalescence afterburner coupled to the well-known $``$A Multi-Phase Transport model" (AMPT). We focus on studying the production of light nuclei in central Au+Au collisions at different center of mass energies ($\sqrt{s_{_{\rm{NN}}}}$ = 19.6, 39, and 200 GeV) and in Pb+Pb collisions at $\sqrt{s_{_{\rm{NN}}}}$ = 2.76 TeV, at mid-rapidity. We generate events with the string melting version of AMPT, and feed the information of the nucleons with spatial and momentum conditions into the coalescence afterburner. Our study reports differential and integrated yields in transverse momentum ($p_{\rm{T}}$) of the light nuclei in different center of mass energies. We also estimate the coalescence parameters ($B_A$) as a function of $p_{\rm{T}}$ and collision energy for (anti-)deuterons, tritons and helium-3s for Au+Au and Pb+Pb collisions, which are compared to other light nuclei production studies. All results are compared with measurements from the STAR and ALICE experiments.

hep-ph↗
arXiv2023

Separation of electrons from pions in GEM TRD using deep learning

Machine learning (ML) is no new concept in the high-energy physics community, in fact, many ML techniques have been employed since the early 80s to deal with a broad spectrum of physics problems. In this paper, we present a novel technique to separate electrons from pions in the Gas Electron Multiplier Transition Radiation Detector (GEM TRD) using deep learning. The Artificial Neural Network (ANN) model is trained on the Monte Carlo data simulated using the ATHENA-based detector and simulation framework for the Electron-Ion Collider (EIC) experiment. The ANN model does a good job of separating electrons from pions.

physics.ins-det↗
arXiv2023

Jet fragmentation via azimuthal angular correlations of heavy-flavours in $pp$ collisions at $\sqrt{s} = $ 7 TeV

Measurements in heavy-flavour azimuthal angular correlation provide insight into the production, propagation, and hadronization of heavy-flavour jets in ultra-relativistic hadronic and heavy-ion collisions. These measurements across different particle species help to isolate the possible modification in particle production and fragmentation due to different mass and quark contents. Jet correlation studies give direct access to the initial parton dynamics produced in these collisions. \\ This article studies the azimuthal angular correlations of heavy-flavour hadrons (charm and beauty mesons and charm baryons) in pp collisions at $\sqrt{s} =$ 7 TeV using PYTHIA8. We study the production of heavy-flavour jets with different parton-level processes, including multi-parton interactions and different color reconnection prescriptions. The heavy-flavour hadrons correlations are calculated in the different triggers and associated \pt intervals to characterize the impact of hard and soft scattering. The yields and the widths associated with the near-side (NS) and away-side (AS) correlation peaks are calculated and studied as a function of associated \pt for different trigger \pt ranges.

hep-ph↗
arXiv2023

Jet fragmentation via azimuthal angular correlations of heavy flavor decay electrons in pp, p--Pb, and Pb--Pb collisions using PYTHIA8+Angantyr

Measurements in heavy flavor azimuthal angular correlation provide insight into the production, propagation, and hadronization of heavy flavor jets in ultra-relativistic hadronic and heavy-ion collisions. These measurements across different colliding systems, like p--A and A--A, help us isolate the possible modification in particle production due to cold nuclear matter (CNM) effects and the formation of Quark-Gluon Plasma (QGP), respectively. Jet correlation studies give direct access to the initial parton dynamics produced in these collisions. This article studies the azimuthal angular correlations of electrons from heavy flavor hadron decays in pp, p--Pb, and Pb--Pb collisions at $\sqrt{s_\rm{NN}} =$ 5.02 TeV using PYTHIA8+Angantyr. We study the production of heavy flavor jets with different parton level processes, including multi-parton interactions, different color reconnection prescriptions, and initial and final state radiation processes. In addition, we add the hadron-level processes, i.e., Bose-Einstein and rescattering effects, to quantify the effect due to these processes. The heavy flavor electron correlations are calculated in the different trigger and associated $p_\rm{T}$ intervals to characterize the impact of hard and soft scattering in the various colliding systems. The yields and the sigmas associated with the near-side (NS) and away-side (AS) correlation peaks are calculated and studied as a function of associated $p_\rm{T}^{assoc}$ for different trigger $p_\rm{T}^{e}$ ranges.

hep-ph↗
arXiv2022

Gamma-hadron Separation in Imaging Atmospheric Cherenkov Telescopes using Quantum Classifiers

In this paper we have introduced a novel method for gamma hadron separation in Imaging Atmospheric Cherenkov Telescopes (IACT) using Quantum Machine Learning. IACTs captures images of Extensive Air Showers (EAS) produced from very high energy gamma rays. We have used the QML Algorithms, Quantum Support Vector Classifier (QSVC) and Variational Quantum Classifier (VQC) for binary classification of the events into signals (Gamma) and background(hadron) using the image parameters. MAGIC Gamma Telescope dataset is used for this study which was generated from Monte Carlo Software Coriska. These quantum algorithms achieve performance comparable to standard multivariate classification techniques and can be used to solve variety of real-world problems. The classification accuracy is improved by hyper parameter tuning. We propose a new architecture for using QSVC efficiently on large datasets and found that clustering enhance the overall performance.

astro-ph.IM↗
arXiv2022

Dynamics of Hot QCD Matter -- Current Status and Developments

The discovery and characterization of hot and dense QCD matter, known as Quark Gluon Plasma (QGP), remains the most international collaborative effort and synergy between theorists and experimentalists in modern nuclear physics to date. The experimentalists around the world not only collect an unprecedented amount of data in heavy-ion collisions, at Relativistic Heavy Ion Collider (RHIC), at Brookhaven National Laboratory (BNL) in New York, USA, and the Large Hadron Collider (LHC), at CERN in Geneva, Switzerland but also analyze these data to unravel the mystery of this new phase of matter that filled a few microseconds old universe, just after the Big Bang. In the meantime, advancements in theoretical works and computing capability extend our wisdom about the hot-dense QCD matter and its dynamics through mathematical equations. The exchange of ideas between experimentalists and theoreticians is crucial for the progress of our knowledge. The motivation of this first conference named "HOT QCD Matter 2022" is to bring the community together to have a discourse on this topic. In this article, there are 36 sections discussing various topics in the field of relativistic heavy-ion collisions and related phenomena that cover a snapshot of the current experimental observations and theoretical progress. This article begins with the theoretical overview of relativistic spin-hydrodynamics in the presence of the external magnetic field, followed by the Lattice QCD results on heavy quarks in QGP, and finally, it ends with an overview of experiment results.

nucl-th↗
arXiv2022

Effect of various particlization scenarios on anisotropic flow and particle production using UrQMD hybrid model

We discuss the effect of various particlization scenarios available in the hybrid ultrarelativistic quantum molecular dynamics (UrQMD) event generator on different observables in non-central ($b$ $=$ 5--9 $fm$) Au + Au collisions in the beam energy range 1A-158A GeV. Particlization models switch fluid dynamic description to the transport description using various hypersurface criteria. In addition to particlization models, various equations-of-state (EoS) provided by the UrQMD hybrid model were employed. The observables examined in this paper include the excitation function of anisotropic coefficients such as directed ($v_{1}$) and elliptic flow ($v_{2}$), particle ratios of the species, and the shape of net-proton rapidity spectra at mid-rapidity. The results obtained here can help predict and compare the measurements provided by future experiments at the Facility for Antiproton and Ion Research (FAIR) and the Nuclotron-based Ion Collider fAcility (NICA) once the data becomes available. We also study the most suitable combination of the particlization model and EoS, which best describes the experimental measurements.

nucl-th↗
arXiv2022

Development of a water-based cooling system for the Muon Chamber detector system of the CBM experiment

A water-based cooling system is being investigated to meet the cooling requirement of the Gas Electron Multiplier (GEM) based Muon Chamber (MuCh) detector system of the Compressed Baryonic Matter (CBM) experiment at GSI, Germany. The system is based on circulating cold water through the channels inside an aluminium plate. The aluminium plate is attached to a GEM chamber. A feasibility study is conducted on one small and two real-size prototype cooling plates. A microcontroller based unit has been built and integrated into the system to achieve automatic control and monitoring of temperature on plate surface. The real-size prototypes have been used in a test beam experiment at the CERN SPS (Super Proton Synchrotron) with the lead beam on a lead target. A setup using three prototype modules has been prepared in the lab for testing in a simulated real life environment. This paper discusses the working principle, mechanical design, fabrication, and test results of the cooling prototypes in detail.

physics.ins-det↗
arXiv2021

Dynamics of particle production in Pb--Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV using PYTHIA8 Angantyr model

We study the dynamics of identified, strange, and multi-strange particle production in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV using the recently developed Angantyr model, incorporated within PYTHIA8. We show the interplay between multi-parton interactions (MPI) and color reconnection (CR) on the experimentally measured quantities. The charged-particle multiplicity ($N_{\rm ch}$) and mean transverse momentum ($\langle p_{\rm T}\rangle$) distributions are well explained by PYTHIA8 Angantyr with proper tuning, as presented in this paper. Predictions of $p_{\rm T}$ spectra, $\langle p_{\rm T} \rangle$, $p_{\rm T}$ integrated yields of the identified, strange and multi-strange particles are studied. To provide insight into the collective nature of the produced particles, we look into the ratio of particle yields to pions and kaons. PYTHIA8 Angantyr with CR and MPI mimic signs of collectivity and is possibly one of the suitable candidates to study ultra-relativistic heavy-ion collisions.

nucl-th↗
arXiv2021

Dependence on beam energy and nuclear equation of state dependence of anisotropic flow and particle production in low-energy heavy-ion collisions

We analyse various flow coefficients of anisotropic momentum distribution of final state particles in mid-central ($b$ $=$ 5--9 $fm$) Au + Au collisions in the beam energy range $\rm E_{\rm Lab}$ $=$ $1A -158A$ GeV. Different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode, are employed for this investigation. In the hybrid UrQMD model, the ideal hydrodynamical evolution is integrated with the pure transport calculation for description of the evolution of the fireball. We opt for the different available equations of state (EoS) replicating the hadronic as well as partonic degrees of freedom together with possible phase transitions, viz. hadron gas, chiral + deconfinement EoS and bag model EoS, to investigate their effect on the properties of the final state particles. We also attempt to gain insights about the dynamics of the medium by studying different features of particle production such as particle ratios and net-proton rapidity distribution. The results and conclusions drawn here would be useful to understand the response of various observables to the underlying physics of the model as well as to make comparisons with the upcoming measurements of the future experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

nucl-th↗
arXiv2020

Hierarchy of kinetic freeze-out parameters in low energy heavy-ion collisions

We study the mass dependent hierarchy of kinetic freeze-out parameters of hadrons in low energy heavy-ion collisions. For this purpose, the transverse momentum and rapidity spectra of the identified hadrons produced in central Pb+Pb collisions, available at SPS energies ranging from $\rm E_{Lab}=20A-158A $ GeV, are analyzed within a generalized non boost-invariant blast wave model. We consider separate simultaneous fits for light hadrons ($π^{-}$, $K^{\pm}$) and heavy strange hadrons ($Λ$, $\barΛ$, $ϕ$, $Ξ^{\pm}$, $Ω^{\pm}$), for which the transverse momentum spectra as well as rapidity spectra are available. We also perform a separate fit to transverse momentum spectra of charmonia ($J/Ψ$, $Ψ'$) at $158A $ GeV collisions. We find a clear mass dependent hierarchy in the fitted kinetic freeze-out parameters. Further, we study the rapidity spectra using analytical Landau flow solution for non-conformal systems. We find that the fitted value of sound velocity in the medium also shows a similar hierarchy.

hep-ph↗
arXiv2019

Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state

In this article, we examine the equation of state (EoS) dependence of the anisotropic flow parameters ($v_{1}$, $v_{2}$ and $v_{4}$) of charged and identified hadrons, as a function of transverse momentum ($p_{\rm T}$), rapidity ($y_{c.m.}$) and the incident beam energy ($\rm E_{\rm Lab}$) in mid-central Au + Au collisions in the energy range $\rm E_{\rm Lab} = 6 -25$ A GeV. Simulations are carried out by employing different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode. In the hybrid mode, transport calculations are coupled with the ideal hydrodynamical evolution. Within the hydrodynamic scenario, two different equations of state (EoS) viz. Hadron gas and Chiral + deconfinement EoS have been employed separately to possibly mimic the hadronic and partonic scenarios, respectively. It is observed that the flow parameters are sensitive to the onset of hydrodynamic expansion of the fireball in comparison to the pure transport approach. The results would be useful as predictions for the upcoming low energy experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

nucl-th↗
arXiv2018

Kinetic freeze out conditions in nuclear collisions with $2A$ - $158A$ GeV beam energy within a non-boost-invariant blast-wave model

We study the kinetic freeze out conditions of bulk hadrons in nuclear collisions. The transverse and longitudinal momentum spectra of the identified hadrons produced in central Au+Au and Pb+Pb collisions, in the beam energy range of $E_b = 2A - 158 A$ GeV are analysed for this purpose, within a generalised non boost-invariant blast wave model. The kinetic freeze out temperature is found to vary in the range of 55 - 90 MeV, whereas the average transverse velocity of collective expansion is found to be around $0.5c$ to $0.6c$. The mean longitudinal velocity of the fireball is seen to increase monotonically with increasing longitudinal boost. The results would be useful to understand the gross collision dynamics for the upcoming experiments at the FAIR and NICA accelerator facilities.

nucl-th↗