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B. K. Patra

Publications and source records attributed to B. K. Patra.

13 recordsLinked to original sources
arXiv2009

Dissociation of 1 p quarkonium states in a hot QCD medium

We extend the analysis of a very recent work (Phys. Rev. {\bf C 80}, 025210 (2009)) to study the dissociation phenomenon of 1p states of the charmonium and bottomonium spectra ($χ_c$ and $χ_b$) in a hot QCD medium. This study employed a medium modified heavy quark potential which is obtained by incorporating both perturbative and non-perturbative medium effects encoded in the dielectric function to the full Cornell potential. The medium modified potential has a quite different form (a long range Coulomb tail in addition to the usual Yukawa term) compared to the usual picture of Debye screening. We further study the flavor dependence of their binding energies and dissociation temperatures by employing the perturbative, non-perturbative, and the lattice parametrized form of the Debye masses. These results are consistent with the predictions of the current theoretical works.

nucl-th↗
arXiv2007

Comment on the paper "Energy Loss of Charm Quarks in the Quark-Gluon Plasma : Collisional vs Radiative"

In the article by M. G. Mustafa published in Phys. Rev. C {\bf 72}, 014905 (2005) the author has estimated the total energy loss of a charm quark and quenching of hadron spectra due to the collisional energy loss of energetic partons in an expanding quark-gluon plasma employing Fokker-Planck equation. We wish to point out through this Comment that some of conceptual and numerical results of the said paper are unreliable. For the sake of clarity our discussion will focus on the massless case (although a few remarks on the $m\neq 0$ case are also made).

hep-ph↗
arXiv2007

Quenching of Hadron Spectra in a chemically equilibrating Quark-Gluon Plasma

Using the Fokker-Planck equation we have studied the drag co-efficient $A(t)$ and the consequent shift $Δp_\perp (L)$ in the transverse momentum due to collisional energy loss of energetic partons while passing through a chemically equilibrating quark-gluon plasma. Based on these we estimate the quenching factor $Q(p_\perp)$ when the medium is undergoing longitudinal expansion governed by master rate equations. In contrast to the case of chemically equilibrated plasma investigated earlier by Mustafa and Thoma \cite{mus} we find less quenching because our calculated $Q(p_\perp)$ is always greater at all momenta. This result is attributed to the weak drag coefficient operating during initial state interactions.

hep-ph↗
arXiv2006

J/ψ$ Gluonic Dissociation Revisited : III. Effects of Transverse Hydrodynamic Flow

In a recent paper [Eur. Phys. J {\bf C 44}, 567 (2005)] we developed a very general formulation to take into account explicitly the effects of hydrodynamic flow profile on the gluonic breakup of $J/ψ$'s produced in an equilibrating quark-gluon plasma. Here we apply that formulation to the case when the medium is undergoing cylindrically symmetric {\it transverse} expansion starting from RHIC or LHC initial conditions. Our algebraic and numerical estimates demonstrate that the transverse expansion causes enhancement of local gluon number density $ŋ$, affects the $\pt$-dependence of the average dissociation rate $\tilg$ through a partial-wave interference mechanism, and makes the survival probability $\spt$ to change with $\pt$ very slowly. Compared to the previous case of longitudinal expansion the new graph of $\spt$ is pushed up at LHC, but develops a rich structure at RHIC, due to a competition between the transverse catch-up time and plasma lifetime.

nucl-th↗
arXiv2005

$J/ψ$ Gluonic Dissociation Revisited : II. Hydrodynamic Expansion Effects

We explicitly take into account the effect of hydrodynamic expansion profile on the gluonic breakup of $J/ψ$'s produced in an equilibrating parton plasma. Attention is paid to the space-time inhomogeneities as well as Lorentz frames while deriving new expressions for the gluon number density $n_g$, average dissociation rate $<\tildeΓ>$, and $ψ$ survival probability $S$. A novel type of partial wave {\em interference} mechanism is found to operate in the formula of $<\tildeΓ>$. Nonrelativistic longitudinal expansion fro small length of the initial cylinder is found to push the $S(p_T)$ graph above the no flow case considered by us earlier \cite{rev1}. However, relativistic flow corresponding to large length of the initial cylinder pushes the curve of $S(p_T)$ downwards at LHC but upwards at RHIC. This mutually different effect on $S(p_T)$ may be attributed to the different initial temperatures generated at LHC and RHIC.

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arXiv2004

$J/ψ$ Gluonic Dissociation Revisited : I. Fugacity, Flux And Formation Time Effects

We revisit the standard treatment [Xu, Kharzeev, Satz and Wang, Phys. Rev. C {\bf 53}, 3051 (1996)] of $J/ψ$ suppression due to gluonic bombardment in an equilibrating quark-gluon plasma. Effects arising from gluon fugacity, relative $g-ψ$ flux, and $ψ$ meson formation time are correctly incorporated in the formulation of the gluon number density, velocity-weighted cross section, and the survival probability. Our new formulae are applied to numerically study the pattern of $J/ψ$ suppression in the central rapidity region at RHIC/LHC energies. The temperature and transverse momentum dependence of our graphs have noticeable differences from those of Xu et al.

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arXiv2002

Spectral Representation at Finite Temperature

This is a short review on the thermal, spectral representation in the real-time version of the finite temperature quantum field theory. After presenting a clear derivation of the spectral representation, we discuss the properties of its spectral function. Two applications of this representation are then considered. One is the solution of the Dyson equation for the thermal propagator. The other is the formulation of the QCD sum rules at finite temperature.

hep-th↗
arXiv2002

Langevin dynamics of $J/ψ$ in a parton plasma

We consider the Brownian motion of a $c \bar c$ pair produced in the very early satge of a quark-gluon plasma. The one-dimensional Langevin equation is solved formally to get purely mechanical properties at small and large times. Stochastically-averaged variances are examined to extract the time scales associated with swelling and ionization of the bound state. Simple numerical estimates of the time scales are compared with other mechanisms of $J/ψ$ suppression.

hep-ph↗
arXiv2002

Space-time evolution of ultra-relativistic heavy ion collisions and hadronic spectra

The space-time evolution of the hot and dense matter formed after the collisions of heavy nuclei at ultra-relativistic energies is investigated using (3+1) dimensional hydrodynamical models. The effects of the spectral shift of the hadronic properties are incorporated in the equation of state (EOS) of the evolving matter. In-medium shift of hadronic properties are considered for Quantum Hadrodynamics (QHD) and universal scaling scenarios. It is found that the EOS for the hadronic matter for universal scaling of hadronic masses (except pseudoscalar mesons) is similar to the recent lattice results. We observe that the space-time volume of the hadronic matter at the freeze-out is considerably different from the one when medium effects on the hadrons are ignored. The sensitivity of the results on the initial radial velocity profile is investigated. The transverse mass spectra of pions and protons of NA49 collaboration are analyzed.

nucl-th↗
arXiv2001

On the Non-Orthonormality of Lippmann-Schwinger-Low States

It is pointed out that for a general short-ranged potential the Lippmann-Schwinger-Low scattering state $|ψ^L_k>$ does not strictly satisfy the Schrodinger eigen equation, and the pair $|ψ^L_n>$, $|ψ^L_k>$ is mutually nonorthogonal if $E_n=E_k$. For this purpose, we carefully use an infinitesimal adiabatic parameter $ε$, a nonlinear relation among transition amplitudes, and a separable interaction as illustration.

quant-ph↗
arXiv1999

Baryon Number Penetrability as a Measure of Isothermal Baryon Number Fluctuations in the Early Universe

We have examined the efficiency of baryon-number transport mechanism across the phase boundary in a cosmological quark-hadron phase transition through the proper estimate of baryon-number penetrability $<Σ_h>$. For this purpose we have derived first the double-pair creation probability $P_b$ in terms of single-pair creation probabilty per unit time and unit volume $κ_m$ and then obtained an analytical expression for $<Σ_h >$. Our calculation is free from the uncertainty of the value of double-pair creation probability per unit time and unit volume $κ_b$ which was used as a free parameter in earlier calculations. Finally the variations of double-pair creation probability $P_b$ as well as $<Σ_h>$ with temperature are shown and compared with other known results.

hep-ph↗
arXiv1998

Large Strangeness as a QGP Signal in an Isentropic Quark-Hadron Phase Transition

Lattice QCD results reveal that the critical parameters and the order of the quark-hadron phase transition are quite sensitive to the number of dynamical flavours and their masses included in the theory. Motivated by this result we develop a phenomenological equation of state for the quark-gluon plasma consisting of $n_f$ flavours retaining the entropy per baryon ratio continuous across the quark-hadron phase boundary. We thus obtain a generalised expression for the temperature and baryon chemical potential dependent bag constant. The results are shown for the realistic case, i.e., involving u, d and s quarks only. We then obtain a phase boundary for an isentropic quark-hadron phase transition using Gibbs' criteria. Similarly another phase boundary is obtained for the transition to an ideal QGP from the solution of the condition $B(μ,T)=0$. The variation of critical temperature $T_c$ with the number of flavours included in the theory. Also the variation of ${(ε-4P)}/T^4$ with temperature are studied and compared with lattice results. Finally the strange particle ratios $\frac{\barΛ}Λ$, $\frac{\barΞ}Ξ$ and $\frac{K^+}{K^-}$ are obtained at both phase boundaries. We propose that their variations with the temperature and baryon chemical potential can be used in identifying the quark-gluon plasma in the recent as well as in future heavy-ion experiments.

hep-ph↗