arXiv subjects

Chitrasen Jena

Publications and source records attributed to Chitrasen Jena.

12 recordsLinked to original sources

arXiv2026

Exploring the properties of the Hadronic Phase in Heavy-Ion Collisions at RHIC Energies via Partial Chemical Equilibrium

The hadronic phase in heavy-ion collisions plays a crucial role in shaping the final-state hadron abundances. In this work, we study Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7-200 GeV using the Hadron Resonance Gas model in Partial Chemical Equilibrium (HRG-PCE). By fitting the yields of stable hadrons and short-lived resonances such as K$^*(892)^0$, we extract both chemical and kinetic freeze-out temperatures as functions of center-of-mass energy and centrality. The analysis, performed using the Thermal-FIST package, avoids assumptions about radial flow profile or freeze-out hypersurfaces. Furthermore, we estimate the baryon annihilation freeze-out temperature from the experimentally measured $\bar{\rm p}/$p ratio, using the HRG-PCE framework extended to include $B\bar{B} \leftrightarrow n\pi$ reactions. The inferred annihilation freeze-out temperature lies between the chemical and kinetic freeze-out temperatures, suggesting that baryon annihilation remains active in the early hadronic phase but ceases prior to kinetic freeze-out. These results provide a consistent picture of the sequential decoupling of hadronic processes and demonstrate that inelastic hadronic interactions significantly influence the chemical composition of the system between chemical and kinetic freeze-outs at RHIC energies.

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arXiv2024

Flavour-Dependent Chemical Freeze-Out of Light Nuclei in Relativistic Heavy-Ion Collisions

We study the production of light nuclei in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7 - 200 GeV and Pb+Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 and 5.02 TeV within a flavour-dependent freeze-out framework, assuming different flavoured hadrons undergo separate chemical freeze-out. Using the Thermal-FIST package, thermal parameters extracted from fits to various sets of hadron yields, including and excluding light nuclei, are used to calculate the ratios of the yields of light nuclei, namely, $d/p$, $\bar{d}/\bar{p}$, $t/p$, and $t/d$. A comparison with data from the STAR and ALICE collaborations shows that a sequential freeze-out scenario provides a better description of light nuclei yield ratios than the traditional single freeze-out approach. These results suggest the flavour-dependent chemical freeze-out for final state light-nuclei production persists in heavy-ion collisions at both RHIC and LHC energies.

hep-ph↗

arXiv2024

Energy dependence of particle production in Au+Au collisions at $\sqrt{s_{\text{NN}}}$ = 7.7-200 GeV using a multiphase transport model

In this study, we employ a multi-phase transport (AMPT) model to understand the production of $\pi^{\pm}$, $K^{\pm}$, $p$, $\overline{p}$, $K^{0}_{s}$, $\Lambda$, $\bar{\Lambda}$, and $\phi$ in Au + Au collisions at $\sqrt{s_{NN}} = 7.7$, $27$, $39$, $62.4$, and $200$ GeV. We have studied the energy dependence of various bulk properties of the system such as transverse momentum ($p_T$) spectra, particle yields ($dN/dy$), mean transverse mass ($\langle m_T \rangle$), and anti-particle to particle ratios. Model calculations using both default and string melting versions of the AMPT with three distinct sets of initial conditions are compared to the data from the STAR experiment. In the case of $\pi^{\pm}$, $K^{\pm}$, $p$, and $\overline{p}$, we observe that the string melting version shows better agreement with data at higher energies, while the default version performs better at lower collision energies. However, for $K^{0}_{s}$, $\Lambda$, and $\phi$, it is observed that the default version is able to describe the data better at all energies. In addition, we have used the blast-wave model to extract the kinetic freeze-out properties, like the kinetic freeze-out temperature and the radial flow velocity. We observe that these parameters are comparable with the data.

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arXiv2024

System size dependence of thermodynamic variables at kinetic freeze-out in high-energy collisions using the Tsallis distribution

We use a thermodynamically consistent form of Tsallis distribution to study the dependence of various thermodynamic quantities on the system size in high-energy collisions. The charged hadron spectra obtained in $p$+$p$, $p$+Pb, Xe+Xe, and Pb+Pb collisions at LHC are used to determine the energy density, pressure, particle density, entropy density, mean free path, Knudsen number, heat capacity, isothermal compressibility, expansion coefficient, and speed of sound at the kinetic freeze-out surface. These quantities are studied as a function of the system size. Notably, the rate of increase (or decrease) in these thermodynamic variables is found to be more rapid in small systems such as $p$+$p$ and $p$+Pb collisions than in large systems such as Xe+Xe and Pb+Pb collisions. This may be due to the small volume of the hadronic system in small collision systems at kinetic freeze-out. It is observed that high-multiplicity $p$+$p$ collisions produce similar thermodynamic conditions as peripheral heavy-ion collisions at kinetic freeze-out.

hep-ph↗

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.

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arXiv2019

Energy Loss Due to Defect Formation from $^{206}$Pb Recoils in SuperCDMS Germanium Detectors

The Super Cryogenic Dark Matter Search experiment (SuperCDMS) at the Soudan Underground Laboratory studied energy loss associated with Frenkel defect formation in germanium crystals at mK temperatures using in situ $^{210}$Pb sources. We examine the spectrum of $^{206}$Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of $\left(6.08\pm0.18\right)$ %, which we attribute to defect formation. From this result and using TRIM simulations, we extract the first experimentally determined average displacement threshold energy of $\left(19.7^{+0.6}_{-0.5}\right)$ eV for germanium. This has implications for the analysis thresholds of future germanium-based dark matter searches.

physics.ins-det↗

arXiv2018

Role of system size on freezeout conditions extracted from transverse momentum spectra of hadrons

The data on hadron transverse momentum spectra in different centrality classes of p+Pb collisions at $\sqrt{s}_{NN} = 5.02$ TeV has been analysed to extract the freezeout hypersurface within a simultaneous chemical and kinetic freezeout scenario. The freezeout hypersurface has been extracted for three different freezeout schemes that differ in the way strangeness is treated: i. unified freezeout for all hadrons in complete thermal equilibrium (1FO), ii. unified freezeout for all hadrons with an additional parameter $γ_S$ which accounts for possible out-of-equilibrium production of strangeness (1FO$+γ_S$), and iii. separate freezeout for hadrons with and without strangeness content (2FO). Unlike in heavy ion collisions where 2FO performs best in describing the mean hadron yields as well as the transverse momentum spectra, in p+Pb we find that 1FO$+γ_S$ with one less parameter than 2FO performs better. This confirms expectations from previous analysis on the system size dependence in the freezeout scheme with mean hadron yields: while heavy ion collisions that are dominated by constituent interactions prefer 2FO, smaller collision systems like proton + nucleus and proton + proton collisions with lesser constituent interaction prefer a unified freezeout scheme with varying degree of strangeness equilibration.

hep-ph↗

arXiv2017

A Review of Elliptic Flow of Light Nuclei in Heavy-Ion Collisions at RHIC and LHC Energies

We present a review of the measurements of elliptic flow ($v_{2}$) of light nuclei ($d$,$\bar{d}$, $t$, $^{3}\rm He$, and $^{3}\overline{\rm He}$) from the RHIC and LHC experiments. Light (anti)nuclei $v_{2}$ have been compared with that of (anti)proton. We observed a similar trend in light nuclei $v_{2}$ to that in identified hadron $v_{2}$ with respect to the general observations such as ($p_{\rm T}$) dependence, low $p_{\rm T}$ mass ordering, and centrality dependence. We also compared the difference of nuclei and antinuclei $v_{2}$ with the corresponding difference of $v_{2}$ of proton and antiproton at various collision energies. Qualitatively they depict similar behavior. We also compare the data on light nuclei $v_{2}$ to various theoretical models such as blast-wave and coalescence. We then present a prediction of $v_{2}$ for $^{3}\rm He$ and $^{4}\rm He$ using coalescence and blast-wave models.

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arXiv2015

Measurements of open-charm production in pp and p-Pb collisions with the ALICE detector at the LHC

Hadrons containing heavy quarks, i.e. charm and beauty, are effective probes to investigate the properties of the hot, dense and strongly-interacting medium formed in high-energy nuclear collisions. The relatively large masses of heavy quarks ensure that they are predominantly produced in the early stages of the collision and probe the complete space-time evolution of the expanding medium. The measurements of D-meson production in pp collisions provide an important test of pQCD calculations and serve as an essential baseline for the comprehensive studies in heavy-ion collisions. The study of D-meson production in p-Pb collisions is necessary to disentangle the cold nuclear matter effects from hot nuclear matter effects. The measurement of heavy-flavour production as a function of charged-particle multiplicity in pp and p-Pb collisions could provide insight into the role of multi-parton interactions at LHC energies. We present ALICE results on D-meson production in pp collisions at $\sqrt{s} =$ 7 TeV and p-Pb collisions at $\sqrt{s_{\rm {NN}}}=$ 5.02 TeV. The D-meson yields per event, measured in different multiplicity intervals and normalized to their multiplicity-integrated values, are presented for pp and p-Pb collisions. The $p_{\rm {T}}$-differential production cross section and nuclear modification factor of prompt D mesons are measured in p-Pb collisions. The nuclear modification factor, $R_\mathrm{pPb}$, is compatible with unity within uncertainties, indicating that cold nuclear matter effects are small for $p_{\mathrm{T}} \gtrsim 3$ GeV/$c$. The D-meson transverse momentum distributions in p-Pb collisions relative to pp collisions, measured in several multiplicity classes, are also discussed.

nucl-ex↗

arXiv2014

Measurement of D-meson production in pp, p-Pb, and Pb-Pb collisions at the LHC with the ALICE detector

Heavy quarks are a powerful probe for investigating the properties of the Quark-Gluon Plasma created in heavy-ion collisions, since they are produced in initial hard scattering processes and experience all the stages of the medium evolution. ALICE has measured the production of $\mathrm{D}^0$, $\mathrm{D}^+$, $\mathrm{D}^{*+}$, and $\mathrm{D}_{\mathrm{s}}^+$ mesons at central rapidity in their hadronic decay channels in various collision systems and energies. We present recent results for D-meson production measured by the ALICE Collaboration in pp collisions at $\sqrt{s}=7$ and 2.76 TeV, Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV and p-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV.

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arXiv2011

Longitudinal scaling of observables in heavy-ion collision models

Longitudinal scaling of pseudorapidity distribution of charged particles ($dN_{\mathrm {ch}}/dη$) is observed when presented as a function of pseudorapidity ($η$) shifted by the beam rapidity ($η$ - $y_{\mathrm {beam}}$) for a wide range of collision systems ($e^{+}+e^{-}$, p+p, $d$+A and A+A) and beam energies. Such a scaling is also observed for the elliptic flow ($v_{2}$) of charged hadrons in A+A collisions. This is a striking observation, as $v_{2}$ is expected to be sensitive to the initial conditions, the expansion dynamics and the degrees of freedom of the system, all of which potentially varies with collision system and colliding energies. We present a study of the longitudinal scalings of $dN_{\mathrm {ch}}/dη$, average transverse momentum ($< p_{\mathrm T}>$) and $v_{2}$ using transport models UrQMD and AMPT for Au+Au collisions at center of mass energies ($\sqrt{s_{\mathrm {NN}}}$) of 19.6, 62.4, 200 GeV and Pb+Pb collisions at 2760 GeV. Only the AMPT models which includes partonic effects and quark coalescence as a mechanism of hadronization, shows longitudinal scaling for $dN_{\mathrm {ch}}/dη$, $< p_{\mathrm T}>$ and $v_{2}$. Whereas the UrQMD and AMPT default versions show longitudinal scaling only for $dN_{\mathrm {ch}}/dη$ and $ $. We also discuss the possibility of longitudinal scaling of $v_{2}$ within two extreme scenarios of models with hydrodynamic and collisionless limits. We find the longitudinal scaling of bulk observables to be an important test for the underlying physics mechanism in models of particle production.

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arXiv2011

Elliptic flow of light nuclei in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

We present the elliptic flow ($v_{2}$) of light nuclei at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. The results are measured in the STAR experiment at RHIC. The $v_{2}$ measurement for light nuclei as a function of transverse momentum $p_{T}$ is found to follow an approximate atomic mass number ($A$) scaling. We compare the measured nuclei $v_{2}$ to results from a dynamical coalescence model calculation. The $v_{2}$ values for light nuclei are further scaled to the number of constituent quarks (NCQ) of their constituent nucleons and are consistent with NCQ scaled $v_{2}$ for baryons and mesons. The dominance of partonic collectivity in the transverse expansion dynamics in these collisions naturally produces such a consistent picture. Similar to other hadrons, an increase of $p_{T}$-integrated $v_{2}$ scaled by the participant eccentricity as a function of collision centrality has been observed.

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