arXiv subjects
Publications and source records attributed to Abhijit Bhattacharyya.
The abundance and size distribution of quark nuggets (QN), formed a few microseconds after the big bang due to first order QCD phase transition in the early universe, has been estimated. It appears that stable QNs could be a viable candidate for cosmological dark matter. The evolution of baryon inhomogeneity due to evaporated (unstable) QNs are also examined.
We calculate the size distribution of quark nuggets, which could be formed due to first order QCD phase transition in the early universe. We find that there are a large number of stable Quark Nuggets which could be a viable candidate for cosmological dark matter.
Two recent experiments have demonstrated that the effective $ρ$-mass in nuclear medium, as extracted from the $^3He(γ, π^+ π^-)$ reaction, is substantially reduced. This has been advocated as an indication of partial restoration of chiral symmetry in nuclear matter. We show that even in the absence of chiral symmetry, effective mean field nuclear matter models can explain these findings quantitatively.
The temperature and density dependence of the $ρ-ω$ mixing amplitude has been studied from a purely hadronic model. The in-medium baryon masses and chemical potentials have been obtained at the Mean Field (MF) Level and these results have been used to calculate the mixing amplitude. It has been observed that the mixing amplitude changes substantially at high temperature and density.
We present a microscopic approach to dynamical pionisation of the hot quark-gluon matter formed in ultrarelativistic heavy ion collisions. The time evolution of the system is described assuming that quarks undergo Brownian motion in a thermal bath provided by the gluons. The rate of hadronization as well as the time dependence of the temperature of the system are seen to be quite sensitive to the QCD $Λ$ parameter. Even in a non-equilibrium scenario, we find that there appears a clear hint of a first order phase transition.
Pion and kaon dissociation in a medium of hot quark matter is studied in the Nambu Jona-Lasinio model. The decay width of pion and kaon are found to be large but finite at temperatures much higher than the so called critical temperature of chiral or deconfinement transition, kaon decay width being larger. Consequently, pions and even kaons (with a lower density compared to pions) should coexist with quarks and gluons at such high temperatures. The implication of the above result in the study of Quark-Gluon plasma is discussed.
Pion dissociation in a medium of hot quark matter is studied. The decay width of pion is found to be large but finite at temperatures much higher than the so called critical temperature of chiral or deconfinement transition. Consequently, pions should coexist with quarks and gluons at such high temperatures. The result is in agreement with the lattice calculations. The implication of the above result in the study of Quark-Gluon plasma is discussed.
The properties of baryonic matter have been investigated at finite density and temperature using different models. The variation of baryon masses and fractional number densities with baryon density and temperature obtained from different models have been compared. The quark hadron phase transition have been studied using Chiral Colour Dieletric (CCD) model in the quark sector. No phase transition has been seen for the different variants of the Zimanyi-Moszkowski model. However, a phase transition is observed for the linear and non-linear Walecka model.
The variation of kaon mass in dense, charge-neutral baryonic matter at beta-equilibrium has been investigated. The baryon interaction has been included by means of nonlinear Walecka model, with and without hyperons and the interaction of kaons with the baryons has been incorporated through the Nelson-Kaplan model. A self-consistant, one-loop level calculation has been carried out. We find that at the mean field level, the presence of the hyperons makes the density-dependence of the kaon mass softer. Thus, the kaon condensation threshold is pushed up in the baryon density. The loop diagrams tend to lower the kaon condensation point for lower values of $a_3 m_s$. We also find that the S-wave kaon-nucleon interaction plays the dominant role in determining the on-set of kaon condensation and the contribution of the P-wave interaction is insignificant.
Effects of finite temperature correction to the dilepton emission rate in ultrarelativistic heavy ion collisions have been looked into. It has been seen that although the $ρ$-peak in the dilepton spectra from the hadronic sector is suppressed at very high temperatures, almost no effect can be observed in the space time integrated count rate.
An extended version of the Zimanyi-Moskowski (ZM) model has been used to calculate the temperature dependence of the hadronic masses. The calculation of meson masses in the Random Phase Approximation (RPA) gives an increase in the $σ$, $ω$ and $π$ effective masses with temperature.
The temperature dependence of the $ϕ$ meson mass and its decay width ($ϕ\rightarrow K \bar{K}$)have been studied from an effective non-linear chiral Lagrangian in $SU(3)$. Effective mass has been obtained from the pole position of the full propagator. The width has also been calculated. It has been found that the mass decreases with temperature very slowly whereas the decay width increases quite sharply. Possible consequence on the QGP signals is discussed.