arXiv subjects

Abhijit Bhattacharyya

Publications and source records attributed to Abhijit Bhattacharyya.

At least 37 records · Page 2Linked to original sources

arXiv2020

Effects of hadronic repulsive interactions on the fluctuations of conserved charges

We investigate the effects of repulsive interaction between hadrons on the fluctuations of the conserved charges. We calculate the baryon,the electric charge and the strangeness susceptibilities within the ambit of hadron resonance gas model extended to include the short range repulsive interactions.The repulsive interactions are included through a mean-field approach where the single particle energy gets modified due to mean field interactions between hadrons proportional to the number density of hadrons.We assume different mean-field interactions for mesons and baryons. It is shown that the repulsive interactions play a very crucial role to describe hadronic matter near transition temperature. We also show that in order to consistently describe higher order conserved charge fluctuations mesonic repulsive interactions cannot be neglected. Further, we demonstrate that the repulsive interaction of baryons are essential to describe the lattice simulation results at finite baryonchemical potential for higher order fluctuations.

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arXiv2020

Interacting hadron resonance gas model in magnetic field and the fluctuations of conserved charges

In this paper we discuss the interacting hadron resonance gas model in presence of a constant external magnetic field. The short range repulsive interaction between hadrons are accounted through van der Waals excluded volume correction to the ideal gas pressure. Here we take the sizes of hadrons as $r_π$ (pion radius) $= 0$ fm, $r_K$ (kaon radius) $= 0.35$ fm, $r_m$ (all other meson radii) $= 0.3$ fm and $r_b$ (baryon radii) $= 0.5$ fm. We analyse the effect of uniform background magnetic field on the thermodynamic properties of interacting hadron gas. We especially discuss the effect of interactions on the behaviour of magnetization of low temperature hadronic matter. The vacuum terms have been regularized using magnetic field independent regularization scheme. We find that the magnetization of hadronic matter is positive which implies that the low temperature hadronic matter is paramagnetic. We further find that the repulsive interactions have very negligible effect on the overall magnetization of the hadronic matter and the paramagnetic property of the hadronic phase remains unchanged. We have also investigated the effects of short range repulsive interactions as well as the magnetic field on the baryon and electric charge number susceptibilities of hadronic matter within the ambit of excluded volume hadron resonance gas model.

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arXiv2020

Dynamical spectral structure of density fluctuation near QCD critical point

The expression for the dynamical spectral structure of the density fluctuation near the QCD critical point has been derived using linear response theory within the purview of Israel-Stewart relativistic viscous hydrodynamics. The change in spectral structure of the system as it moves toward critical end point has been studied. The effects of the critical point have been introduced in the system through a realistic equation of state and the scaling behaviour of various transport coefficients and thermodynamic response functions. We have found that the Brillouin and the Rayleigh peaks are distinctly visible when the system is away from critical point but the peaks tend to merge near the critical point. The sensitivity of structure of the spectral function on wave vector ($k$) of the sound wave has been demonstrated. It has been shown that the Brillouin peaks get merged with the Rayleigh peak because of the absorption of sound waves in the vicinity of the critical point.

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arXiv2020

Dispersion and suppression of sound near QCD critical point

We have used second order relativistic hydrodynamics equipped with equation of state which includes the critical point to study the propagation of perturbation in a relativistic QCD fluid. Dispersion relation for the sound wave has been derived to ascertain the fate of the perturbation in the fluid near the QCD critical end point (CEP). We observe that the threshold value of the wavelength of the sound in the fluid diverges at the CEP, implying that all the modes of the perturbations are dissipated at this point. Some consequences of the suppression of sound near the critical point have been discussed.

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arXiv2019

Finite temperature properties of a modified Polyakov$-$Nambu$-$Jona-Lasinio model

Thermodynamic properties of strongly interacting matter are investigated using the Polyakov loop enhanced Nambu$-$Jona-Lasinio model along with some modifications to include the hadrons. Various observables are shown to have a close agreement with the numerical data of QCD on lattice. The advantage of the present scheme over a similar study using a switching function is that here no extra parameters are to be fitted. As a result the present scheme can be easily extended for finite chemical potentials.

hep-ph↗

arXiv2019

Suppression of quarkonia in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

We study different processes responsible for the modification of quarkonia yields in the medium produced in PbPb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The quarkonia and heavy flavour cross sections are estimated using the measurements in pp collisions at LHC energies and shadowing corrections are obtained using the EPS09 parametrizations. A kinetic model is used which incorporates quarkonia suppression inside the Quark Gluon Plasma (QGP), suppression due to hadronic comovers, and regeneration from recombination of heavy quark pairs. The quarkonia dissociation cross section due to gluon collisions, including both color-electric dipole and color-magnetic dipole transitions, has been employed. The regeneration rate is obtained using the principle of detailed balance. The effect of these processes on the nuclear modification factors for both $\Jpsi$ and $Υ$ in different ranges of transverse momentum $\pT$ and rapidity has been studied for PbPb collisions at $\sNN =$ 5.02 TeV. The calculations are compared with the available results from LHC experiments. Both the suppression and regeneration due to a QGP are effective in the low and intermediate $\pT$ range. The large observed suppression of $\Jpsi$ at $\pT~>$ 10 GeV/$c$ is larger than the suppression expected due to gluon dissociation.

hep-ph↗

arXiv2018

$Ψ(2s)$ production in $p+A$ collisions

We have analyzed the data on $ψ'$ production in proton-nucleus ($p+A$) collisions, available from the NA50 Collaboration in the SPS energy domain. The investigated data sets include the absolute production cross sections as well as $ψ'$-to-Drell Yan (DY) cross section ratios. An adapted version of two component QVZ model has been employed to calculate $ψ'$ production cross sections. For both $ψ'$ and DY production, nuclear modifications to the free nucleon structure functions are taken into account. For $ψ'$, final state interaction of the produced $c\bar{c}$ pairs with the nuclear medium is also taken into account, in accordance with the previously analyzed $J/ψ$ data. A satisfactory description of the data in $p+A$ collisions is obtained. Model calculations are extrapolated to low energy regime to predict the $ψ'$ suppression in proton induced collisions at near threshold energies.

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arXiv2018

Effects of a non-zero strangeness-chemical potential in strong interaction models

The effect of a non-zero strangeness chemical potential on the strong interaction phase diagram has been studied within the framework of the SU(3) quark-hadron chiral parity-doublet model. Both, the nuclear liquid-gas and the chiral/deconfinement phase transitions are modified. The first-order line in the chiral phase transition is observed to vanish completely, with the entire phase boundary becoming a crossover. These changes in the nature of the phase transitions are expected to modify various susceptibilities, the effects of which might be detectable in particle-number distributions resulting from moderate-temperature and high-density heavy-ion collision experiments.

hep-ph↗

arXiv2017

Thermodynamics of strongly interacting matter in a hybrid model

The equation of state and fluctuations of conserved charges in a strongly interacting medium under equilibrium conditions form the baseline upon which various possible scenarios in relativistic heavy-ion collision experiments are built. Many of these quantities have been obtained in the lattice QCD framework with reliable continuum extrapolations. Recently the Polyakov$-$Nambu$-$Jona-Lasinio model has been reparametrized to some extent to reproduce quantitatively the lattice QCD equation of state at vanishing chemical potentials. The agreement was precise except at low temperatures, possibly due to inadequate representation of the hadronic degrees of freedom in the model. This disagreement was also observed for some of the fluctuation and correlations considered. Here we address this issue by introducing the effects of hadrons through the Hadron Resonance Gas model. The total thermodynamic potential is now a weighted sum of the thermodynamic potential of the Polyakov$-$Nambu$-$Jona-Lasinio model and that of the Hadron Resonance Gas model. We find that the equation of state and the fluctuations and correlations obtained in this hybrid model agrees satisfactorily with the lattice QCD data in the low temperature regime.

hep-ph↗

arXiv2017

Reparametrizing the Polyakov$-$Nambu$-$Jona-Lasinio model

The Polyakov$-$Nambu$-$Jona-Lasinio model has been quite successful in describing various qualitative features of observables for strongly interacting matter, that are measurable in heavy-ion collision experiments. The question still remains on the quantitative uncertainties in the model results. Such an estimation is possible only by contrasting these results with those obtained from first principles using the lattice QCD framework. Recently a variety of lattice QCD data were reported in the realistic continuum limit. Here we make a first attempt at reparametrizing the model so as to reproduce these lattice data. We find excellent quantitative agreement for the equation of state. Certain discrepancies in the charge and strangeness susceptibilities as well as baryon-charge correlation still remain. We discuss their causes and outline possible directions to remove them.

hep-ph↗

arXiv2017

Polyakov--Nambu--Jona-Lasinio model in finite volumes

We discuss the 2+1 flavor Polyakov loop enhanced Nambu--Jona-Lasinio model in a finite volume. The main objective is to check the volume scaling of thermodynamic observables for various temperatures and chemical potentials. We observe the possible violation of the scaling with system size in a considerable window along the whole transition region in the $T-μ_q$ plane.

hep-ph↗

arXiv2016

Exploring effects of magnetic field on the Hadron Resonance Gas

We present a study of the effects of magnetic fields on fluctuations and correlations in hadron resonance gas model. We find significant changes in the fluctuations of net baryon number, electric charge and strangeness. This is also reflected in various fluctuation ratios along the freezeout curve.

hep-ph↗

arXiv2016

Microscopic folding model analysis of the radiative $(n,γ)$ reactions near the $Z=28$ shell-closure and the weak s-process

The radiative thermal neutron capture cross sections over the range of thermal energies from 1 keV to 1 MeV are studied in statistical Hauser-Feshbach formalism. The optical model potential is constructed by folding the density dependent M3Y nucleon-nucleon interaction with radial matter densities of target nuclei obtained from relativistic-mean-field (RMF) theory. The standard nuclear reaction code TALYS1.8 is used for calculation of cross sections. The nuclei studied in the present work reside near the $Z=28$ proton shell closure and are of astrophysical interests taking part in p-, s-, and r-process of nucleosynthesis. The Maxwellian-averaged cross-section (MACS) values for energies important for astrophysical applications are presented.

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arXiv2016

Microscopic potential model analysis of the radiative $(n,γ)$ cross sections near the $Z=50$ shell closure taking part in the main s-component

The neutron capture cross sections have been studied near the $Z=50$ closed shell for a number of nuclei those take part in heavy element nucleosynthesis, the slow and the rapid neutron capture processes and the proton capture process. An optical model potential is constructed in theoretical approach by folding the density dependent M3y purely real nucleon-nucleon interaction with the target radial matter density in relativistic mean field (RMF) approach. The standard code TALYS1.8 is used for cross-section calculation. We have presented the Maxwellian-averaged capture cross-section (MACS) values and stellar neutron capture reaction rates at astrophysically relevant thermal energies and temperatures.

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arXiv2016

Radiative proton capture cross sections in the mass range $40-55$

Proton capture cross sections in the energy range of astrophysical interest for mass region 40-54 have been calculated in the Hauser-Feshbach formalism with reaction code TALYS1.6. The density dependent M3Y effective nucleon-nucleon interaction folded with target radial matter densities from relativistic mean field approach is used to obtain the semi-microscopic optical potential. A definite normalization of potential-well depths has been used over the entire mass region. The $(p,γ)$ rates of some reactions, important in the astrophysical scenario, are calculated using the potential in the relevant mass region.

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arXiv2016

Neutron capture reactions relevant to s-process and p-process in the domain of the $N=50$ shell closure

Radiative thermal neutron capture cross sections for nuclei participating in s-process and p-process nucleosynthesis in and around $N=50$ closed neutron shell have been calculated in statistical semi-microscopic Hauser-Feshbach approach for the energy range of astrophysical interest. A folded optical model potential is constructed utilizing the standard DDM3Y real nucleon-nucleon interaction. The folding of the interaction with target radial matter densities, obtained from the relativistic-mean-field approach, is done in coordinate space using the spherical approximation. The standard nuclear reaction code TALYS1.8 is used for cross-section calculation. The cross sections are compared with experimental results and reasonable agreements are found for almost all cases. Maxwellian-averaged cross sections (MACS) for the nuclei are presented at a single thermal energy of 30 keV relevant to s-process. We have also presented the MACS values over a range of energy from 5 to 100 keV for neutron magic nuclei with $(N=50)$.

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arXiv2015

Massive neutron stars with hyperonic core : a case study with the IUFSU model

The recent discoveries of massive neutron stars, such as PSR J$0348+0432$ and PSR J$1614-2230$, have raised questions about the existence of exotic matter such as hyperons in the neutron star core. The validity of many established equations of states (EoS's) like the GM1 and FSUGold are also questioned. We investigate the existence of hyperonic matter in the central regions of massive neutron stars using Relativistic Mean Field (RMF) theory with the recently proposed IUFSU model. The IUFSU model is extended by including hyperons to study the neutron star in $β$ equilibrium. The effect of different hyperonic potentials, namely $Σ$ and $Ξ$ potentials, on the EoS and hence the maximum mass of neutron stars has been studied. We have also considered the effect of stellar rotation since the observed massive stars are pulsars. It has been found that a maximum mass of $1.93M_{\odot}$, which is within the 3$σ$ limit of the observed mass of PSR J$0348+0432$, can be obtained for rotating stars, with certain choices of the hyperonic potentials. The said star contains a fair amount of hyperons near the core.

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arXiv2015

Neutron Capture Reactions near N=82 Shell-Closure

Neutron capture cross-sections have been calculated in nuclei near the N=82 neutron shell closure. These nuclei are of astrophysical interest, participating in s-process and p-process. A semi-microscopic optical model have been used with the potential being obtained through folding the target density with the DDM3Y nucleon nucleon interaction. Theoretical density values have been calculated in the relativistic mean field approach. The calculated cross-section, as a function of neutron energy, agree reasonably well with experimental measurements. Maxwellian averaged cross-sections, important for astrophysical processes, have been calculated.

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