arXiv subjects

Sadhana Dash

Publications and source records attributed to Sadhana Dash.

At least 37 records · Page 2Linked to original sources

arXiv2024

Nonextensive effects on the viscous properties of hot and magnetized QCD matter

We have studied the effect of the nonextensive Tsallis mechanism on the viscous properties of hot QCD matter in the presence of a strong magnetic field. The results are compared to the case of absence of magnetic field. The viscous coefficients, such as the shear viscosity ($η$) and the bulk viscosity ($ζ$) are determined in the similar environment by utilizing the nonextensive Tsallis mechanism within the relaxation time approximation of kinetic theory. We have observed that, when the nonextensive parameter $q$ is just above unity, both shear and bulk viscosities get increased as compared to their counterparts at $q=1$. This enhancement in viscosities is more evident in the additional presence of a strong magnetic field. Furthermore, some observables pertaining to the flow characteristic, fluid behavior and conformal symmetry of the medium are also explored.

hep-ph↗

arXiv2023

Impact of nonextensivity on the transport coefficients of a magnetized hot and dense QCD matter

We have studied the impact of the nonextensivity on the transport coefficients related to charge and heat in thermal QCD. For this purpose, the electrical ($σ_{\rm el}$), Hall ($σ_{\rm H}$), thermal ($κ$) and Hall-type thermal ($κ_{\rm H}$) conductivities are determined using the kinetic theory approach in association with the nonextensive Tsallis statistical mechanism. The effect of nonextensivity is encoded in the nonextensive Tsallis distribution function, where the deviation of the parameter $q$ from 1 signifies the degree of nonextensivity in the concerned system. The thermal and electrical conductivities are found to increase with the introduction of nonextensivity, which means that the deviation of the medium from thermal equilibrium enhances both charge and heat transports. With the magnetic field, the deviations of $σ_{\rm el}$, $σ_{\rm H}$, $κ$ and $κ_{\rm H}$ from their respective equilibrated values increase, whereas these deviations decrease with the chemical potential. We have also studied how the extent of the nonextensivity modulates the longevity of magnetic field. Present work is further extended to the study of some observables associated with the aforesaid transport phenomena, such as the Knudsen number and the elliptic flow within the nonextensive Tsallis framework.

hep-ph↗

arXiv2023

Multiplicity and Transverse Spherocity dependence of $\langle p_{\rm T} \rangle$ fluctuations of charged particles in p$-$p collisions at $\sqrt{s}$ = 7 and 13 TeV

The multiplicity dependence of event-by-event fluctuations in mean transverse momentum, $\langle p_{\rm T} \rangle$, of charged particles has been studied in p$-$p collisions at $\sqrt{s}$ = 7 TeV and 13 TeV using the PYTHIA 8 event generator. The charged particles were selected in kinematic range of $0.15 < p_{\rm T}<2$ GeV$/c$ and $|η| < 0.8$. The dynamical fluctuations would indicate towards the correlated emission of particles. The measurements in A$-$A and p$-$p collisions has shown a decrease in the strength of $ \langle p_{\rm T} \rangle$ fluctuations with the average charged particle multiplicity. The effects of various microscopic processes like color reconnection and multi-partonic interactions has been studied. A minimal dependency on the collision energy is also observed. Furthermore, the fluctuation observables are investigated in the intervals of transverse spherocity in order to comprehend the relative contributions resulting from hard scattering and underlying events. The present study would act as a baseline for future measurements in A$-$A as well as p$-$p collisions at the LHC.

hep-ph↗

arXiv2023

Effects of weak magnetic field and finite chemical potential on the transport of charge and heat in hot QCD matter

We have studied the effects of weak magnetic field and finite chemical potential on the transport of charge and heat in hot QCD matter by estimating their respective response functions, such as the electrical conductivity ($σ_{\rm el}$), the Hall conductivity ($σ_{\rm H}$), the thermal conductivity ($κ_0$) and the Hall-type thermal conductivity ($κ_1$). The expressions of charge and heat transport coefficients are obtained by solving the relativistic Boltzmann transport equation in the relaxation time approximation at weak magnetic field and finite chemical potential. The interactions among partons are incorporated through their thermal masses. We have observed that $σ_{\rm el}$ and $κ_0$ decrease and $σ_{\rm H}$ and $κ_1$ increase with the magnetic field in the weak magnetic field regime. On the other hand, the presence of a finite chemical potential increases these transport coefficients. The effects of weak magnetic field and finite chemical potential on aforesaid transport coefficients are found to be more conspicuous at low temperatures, whereas at high temperatures, they have only a mild dependence on magnetic field and chemical potential. We have found that the presence of finite chemical potential further extends the lifetime of the magnetic field. Furthermore, we have explored the effects of weak magnetic field and finite chemical potential on the Knudsen number, the elliptic flow coefficient and the Wiedemann-Franz law.

hep-ph↗

arXiv2023

Viscous QCD medium effects on the bottom quark transport coefficients

The bottom quark transport coefficients, i.e., drag and diffusion coefficients, have been studied for the collisional and soft gluon radiative processes within the viscous QCD medium. The thermal medium effects are incorporated using the effective fugacity quasiparticle model (EQPM). Both the shear and bulk viscous effects at leading order are embedded through the near-equilibrium distribution functions of the quark-gluon plasma (QGP) constituent quasiparticles. The transport coefficients' dependence on the bottom quark's initial momentum and QGP temperature has been investigated. The relative dominance of the radiative over the collisional process for the bottom quark seems to occur at a higher initial momentum compared to that of the charm quark. In contrast, the effect of the viscous corrections seems to be more for the charm quark.

hep-ph↗

arXiv2022

Flow of charge and heat in thermal QCD within the weak magnetic field limit: A BGK model approach

We have computed the charge and heat transport coefficients of hot QCD matter by solving the relativistic Boltzmann transport equation using the BGK model approximation with a modified collision integral in the weak magnetic field regime. This modified collision integral enhances both charge and heat transport phenomena which can be understood by the large values of the above-mentioned coefficients in comparison to the relaxation collision integral. We have also presented a comparative study of coefficients like the electrical conductivity ($σ_{el}$), Hall conductivity ($σ_{H}$), thermal conductivity ($κ$) and Hall-type thermal conductivity($κ_{H}$) in weak and strong magnetic fields in the BGK model approximation. The effects of weak magnetic field and finite chemical potential on the transport coefficients have been explored using a quasiparticle model. Moreover, we have also studied the effects of weak magnetic field and finite chemical potential on Lorenz number, Knudsen number, specific heat, elliptic flow and Wiedemann-Franz law.

hep-ph↗

arXiv2022

Study of multiplicity dependence of heavy flavor production in p-p collisions using rope hadronization mechanism

The multiplicity dependence of the production of the charm mesons in p$-$p collisions at $\sqrt{s} = 7$ TeV and 13 TeV as measured by ALICE experiment has been investigated using Pythia 8 event generator by studying the effect of various processes at partonic level such as the effect of different modes of color reconnections and rope hadronization. The relative yields ($\rm Yield/\langle Yield \rangle$) of D-mesons and $J/ψ$ as a function of relative charged particle multiplicity for various transverse momentum ($p\textsubscript{T}$) ranges as measured by the ALICE experiment are in reasonable agreement with the estimations of Pythia 8 model within the framework of microscopic processes. The relative yields of B mesons for various $p\textsubscript{T}$ intervals ($1 < p_{T} < 20$ GeV/$c$) have also been predicted in p$-$p collisions at $\sqrt{s} = 7$ TeV and $\sqrt{s} = 13$ TeV.

hep-ex↗

arXiv2022

Momentum transport properties of a hot and dense QCD matter in a weak magnetic field

We have studied the momentum transport properties of a hot and dense QCD matter in the presence of weak magnetic field by determining the shear ($η$) and bulk ($ζ$) viscosities in the relaxation time approximation of kinetic theory. The dependence of $η$ and $ζ$ on the temperature has been explored in the presence of weak magnetic field ($B$-field) and finite chemical potential ($μ$). It is observed that both shear and bulk viscosities get decreased in the presence of a weak magnetic field, whereas the finite chemical potential increases these viscosities, specifically at low temperatures. This study is important to understand the sound attenuation through the Prandtl number (Pr), the nature of the flow through the Reynolds number (Re), the fluidity and location of transition point of the matter through the ratios $η/s$ and $ζ/s$ ($s$ is the entropy density), respectively. The Prandtl number is observed to increase in the weak magnetic field, whereas the presence of a finite chemical potential reduces its magnitude as compared to the scenario of absence of $B$-field and $μ$. However, Pr still remains larger than unity, indicating that the energy dissipation due to the sound attenuation is mostly governed by the momentum diffusion. It is noticed that the weak magnetic field makes the Reynolds number larger, whereas the chemical potential makes it smaller than that in the absence of $B$-field and $μ$. We have observed that the ratio $η/s$ decreases in the weak magnetic field regime, whereas the finite chemical potential increases its value, but the ratio $ζ/s$ is found to decrease in the presence of weak magnetic field as well as finite chemical potential.

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.

nucl-th↗

arXiv2022

Separating Diffractive and Non-Diffractive events in High energy Collisions at LHC energies

The charged particle multiplicity distribution in high energy hadronic and nuclear collisions receive contribution from both diffractive and non diffractive processes. It is experimentally challenging to segregate diffractive events from non-diffractive events. The present work aims to separate and extract the charged particle multiplicity distribution of diffractive and non-diffractive events in hadronic collisions at LHC energies. A data driven model using the topic modelling statistical tool, DEMIX, has been used to demonstrate the proof of concept for p p collisions at 7 TeV generated by Pythia 8 event generator. The study suggests that DEMIX technique can be used to extract the underlying base distributions and fractions for experimental observables pertaining to diffractive and non-diffractive events at LHC energies and can therefore be used as a step forward for an experimental determination of precise inelastic cross-sections in pp collisions.

hep-ph↗

arXiv2022

Effect of color reconnection and hadronic re-scattering on underlying events in pp collisions at LHC energies

Underlying events dominate most of the hadronic activity in p$-$p collisions and are spanned from perturbative to non-perturbative QCD, having a sensitivity ranging from the multi-scale to very low-x scale physics. A detailed understanding of such events plays a crucial role in the accurate understanding of Standard Model ()SM and Beyond Standard Model physics. The underlying event activities has been studied within the framework of Pythia 8 Monte Carlo model, considering the underlying events observables mean charged particle multiplicity density , $\langle d^{2}N /dηdϕ\rangle$ and mean scalar $p_T$ sum, $\langle d^{2} \sum p_{T} /dηdϕ\rangle$ as a function of leading charged particle in towards, away, and transverse region of p$-$p collisions at $\sqrt{s}$ = 2.76, 7 and 13 TeV. The towards, away, and transverse regions have been defined on an azimuthal plane relative to leading particle in p$-$p collisions. The energy dependence of underlying events and their activities in the central and forward region has also been studied. The effect of hadronic re-scattering, color reconnection, and rope hadronization mechanism implemented in Pythia 8 has been studied in details to gain insight into the different processes contributing to underlying events in soft sector.

hep-ph↗

arXiv2021

Heavy quark transport coefficients in a viscous QCD medium with collisional and radiative processes

The heavy quark drag and momentum diffusion coefficients in the presence of both the collisional and radiative processes have been studied in a hot viscous QCD medium. The thermal medium effects are incorporated by employing the effective fugacity quasiparticle model based on the lattice QCD equation of state. Viscous effects are embedded into the heavy quark transport through the near-equilibrium distribution functions of the constituent medium particles of the quark-gluon plasma. The viscous corrections to the momentum distributions have been estimated from the effective Boltzmann equation. The effect of shear viscous correction to drag and diffusion is investigated by considering the soft gluon radiation by heavy quarks along with the elastic collisional processes of the heavy quark with the light quarks and gluons within the QGP medium. The momentum and temperature dependence of the heavy quark transport coefficients are seen to be sensitive to the viscous coefficient of the QGP for the collisional and radiative processes. The collisional and radiative energy loss of the heavy quark in the viscous quark-gluon plasma has also been explored.

hep-ph↗

arXiv2020

Identical-particle (pion and kaon) femtoscopy in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with Therminator2 modeled with (3+1)D viscous hydrodynamics

The three-dimensional femtoscopic correlations of pions and kaons are presented for Pb$-$Pb collisions at \rootsNN = 5.02 TeV within the framework of (3+1)D viscous hydrodynamics combined with THERMINATOR 2 code for statistical hadronization. The femtoscopic radii for pions and kaons are obtained as a function of pair transverse momentum and centrality in all three pair directions. The radii showed a decreasing trend with an increase of pair transverse momentum and transverse mass for all centralities. These observations indicate the presence of strong collectivity. A simple effective scaling of radii with pair transverse mass was observed for both pion and kaons.

hep-ph↗

arXiv2020

Baseline study for net-proton number fluctuations at top energies available at the BNL Relativistic Heavy Ion Collider and at the CERN Large Hadron Collider with the Angantyr model

The multiplicity percentile dependence of cumulants, of net-proton number distributions in Au$-$Au collisions at $\sqrt{s_{NN}} = $ 200 GeV and Pb$-$Pb collisions at $\sqrt{s_{NN}} = $ 2.76 TeV has been investigated using the Angantyr model (the heavy-ion extension of the \textsc{Pythia 8} model). The effects of finite transverse momentum ($p_{\mathrm T}$) and pseudorapidity ($η$) acceptance on the net-proton cumulants have also been studied. Furthermore, the effects of the hydrodynamic expansion and feed down from weak decays were explored. It was found that radial flow has substantial impact on the cumulants and their ratios, while weak decays have a finite but relatively smaller effect. The obtained values of cumulants and their ratios with the Angantyr model, where the formation of thermalized medium is not assumed can serve as a baseline for future measurements.

hep-ph↗

arXiv2020

Understanding long-range near-side ridge correlations in p$-$p collisions using rope hadronization at LHC energies

The observation of long range ridge-like structure in the near-side region of the two particle $Δη-Δϕ$ correlations as measured by LHC experiments in high multiplicity p$-$p collisions indicated towards the presence of collective effects which are similar to that observed in p$-$A(nucleon-nucleus) and A$-$A (nucleus-nucleus) collisions. The two particle correlation between the charged particles in $Δη-Δϕ$ for p$-$p collisions at $\sqrt{s}$ = 7 TeV and 13 TeV is studied using Pythia 8 event generator within the framework of final-state partonic color reconnection effects as well as the microscopic rope hadronization model. The rope hadronization relies on the formation of ropes due to overlapping of strings in high multiplicity events followed by string shoving. A near side ridge-like structure which is qualitatively similar to the observed ridge in data was observed for high-multiplicity events when the mechanism of rope hadronization (with shoving) was enabled.

hep-ph↗

arXiv2019

Effect of color reconnection and rope formation on resonance production in p$-$p collisions in Pythia 8

The resonance production in proton$-$proton collisions at $\sqrt{s}$ = 7 TeV and 13 TeV have been investigated using Pythia 8 event generator within the framework of microscopic processes like color reconnection and rope hadronization. Specifically, the observable effects of different modes of color reconnections on the ratio of yields of mesonic and baryonic resonances with respect to their stable counterpart have been explored as a function of event activity. A suppression in the ratio is observed as a function of number of multi-partonic interactions for mesonic resonances. The $\mathrm{ϕ/K}$ and $\mathrm{ϕ/π}$ ratios show an enhancement for high multiplicity events due to enhanced production of strange quarks via the microscopic process of rope hadronization in the partonic phase. The mechanism of the hadronization of color ropes together with the QCD-based color reconnection of partons predicted an enhancement in the ratio for baryonic resonances to non-resonance baryons having similar quark content. The yield ratios of resonances are found to be independent of the collision energy and strongly dependent on event activity.

hep-ph↗

arXiv2019

Modeling of Charged-Neutral Kaon Fluctuations as a Signature of DCC Production in A--A Collisions

Anomalous event-by-event fluctuations of the relative yields of neutral (K$^0_s$) and charged kaon (K$^\pm$) have been predicted to yield a signature for the formation of Disoriented Chiral Condensate (DCC) in relativistic heavy-ion collisions. In this work, we model the production and decay of DCCs in the context of heavy-ion collisions at the Large Hadron Collider, and estimate the sensitivity of large acceptance detectors, such as the ALICE detector, towards the identification of such anomalous decays. Our study is based on the robust statistical observable, $ν_{\rm dyn}$, known for its sensitivity to dynamical fluctuations. We first present simulations without DCCs, based on the HIJING and AMPT models, in order to establish an approximate reference for the magnitude of $ν_{\rm dyn}({\rm K}^{\pm},{\rm K}^{0}_{s})$ and its centrality evolution in Pb--Pb collisions at the TeV energy scale. We next introduce simple phenomenological models of K$^0_s$ vs. K$^\pm$ event-by-event yield fluctuations, which we use to study the feasibility and sensitivity of detection of the production of DCCs in heavy-ion collisions. Although the precision of models such as HIJING and AMPT limit their use as absolute references and thus render anomalous fluctuations difficult to define precisely, our studies demonstrate that the magnitude of $ν_{\rm dyn}({\rm K}^{\pm},{\rm K}^{0}_{s})$ is in fact very sensitive to the presence of small admixture of DCCs in normal non-DCC events. Consequently, while large values of $ν_{\rm dyn}({\rm K}^{\pm},{\rm K}^{0}_{s})$ may not be sufficient to identify the existence of DCCs, nonetheless they constitute a first and necessary condition to signal their possible production in heavy-ion collisions.

hep-ph↗

arXiv2019

Multiplicity dependence of strange and multi-strange hadrons in p$-$p, p$-$Pb and Pb$-$Pb collisions at LHC energies using Tsallis-Weibull Formalism

The transverse momentum ($p_{T}$) distribution of strange hadrons ($K_{S}^{0}$ and $Λ$) and multi-strange hadrons( $Ξ$ and $Ω$) measured in p$-$p, p$-$Pb, and Pb$-$Pb collisions at LHC energies have been studied for different multiplicity classes using Tsallis-Weibull (or q$-$Weibull)formalism. The distribution describes the measured $p_{T}$ spectra for all multiplicity (or centrality)classes. The multiplicity dependence of the extracted parameters are studied for the mentioned collisions systems. The $λ$ parameter was observed to increase systematically with the collision multiplicity and follows a mass hierarchy for all collision system. This characteristic feature indicates that $λ$ can be associated to the strength of collectivity for heavy ion collisions. It can also be related to strength of dynamic effects such as multi-partonic interactions and color reconnections which mimic collectivity in smaller systems. The non-extensive $q$ parameter is found to be greater than one for all the particles suggesting that the strange particles are emitted from a source which is not fully equilibrated.

hep-ph↗