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Sanjay K. Ghosh

Publications and source records attributed to Sanjay K. Ghosh.

At least 55 records · Page 3Linked to original sources
arXiv2009

Study of low energy hadronic interaction models based on BESS observed cosmic ray proton and antiproton spectra at medium high altitude

We study low energy hadronic interaction models based on BESS observed cosmic ray proton and antiproton spectra at medium high altitude. Among the three popular low energy interaction models, we find that FLUKA reproduces results of BESS observations on secondary proton spectrum reasonably well over the whole observed energy range, the model UrQMD works well at relatively higher energies whereas spectrum obtained with GHEISHA differs significantly from the measured spectrum. Simulated antiproton spectrum with FLUKA, however, exhibits significant deviations from the BESS observation wheras UrQMD and GHEISHA reproduce the BESS observations within the experimental error.

astro-ph.HE↗
arXiv2008

Quark stars: their influence on Astroparticle Physics

We discuss some of the recent developments in the quark star physics along with the consequences of possible hadron to quark phase transition at high density scenario of neutron stars and their implications on the Astroparticle Physics.

astro-ph↗
arXiv2008

Astrophysics of Strange Matter

The QCD phase transition has important consequences in the context of both the early universe as well as compact stars. Such transitions are being studied for high temperature and small chemical potential scenario in the laboratory. There are also plans to study systems with large chemical potential and small temperatures. Here we have reviewed the role of strange quark matter and the phase transition in all the above scenarios.

astro-ph↗
arXiv2008

Conversion of nuclear to 2-flavour quark matter in rotating compact stars: A general relativistic perspective

The conversion of neutron star to strange star is argued to be a two step process. The first process involves the deconfinement of nuclear to two-flavour quark matter. The GR results shows that the propagating front breaks up into fragments which propagate with different velocities along different directions. The time taken for this conversion to happen is of the order of few $ms$. This calculation indicates the inadequacy of non-relativistic (NR) or even Special Relativistic (SR) treatments for these cases.

astro-ph↗
arXiv2008

QGP Susceptibilities from PNJL Model

An improved version of the PNJL model is used to calculate various thermodynamical quantities, {\it viz.}, quark number susceptibility, isospin susceptibility, specific heat, speed of sound and conformal measure. Comparison with Lattice data is found to be encouraging.

hep-ph↗
arXiv2008

PNJL model with a Van der Monde term

We extend the Polyakov-Nambu-Jona-Lasinio (PNJL) model for two degenerate flavours by including the effect of the SU(3) measure with a Van der Monde (VdM) term. This ensures that the Polyakov loop always remains in the domain [0,1]. The pressure, energy density, specific heat, speed of sound and conformal measure show small or negligible effects from this term. However various quark number and isospin susceptibilities are all found to approach their respective ideal gas limits around 2 $T_c$. We compare our methods with other similar approaches in PNJL model and also present a quantitative comparison with Lattice QCD data.

hep-ph↗
arXiv2007

Effect of General Relativity and rotation on the energy deposition rate for $ν+ \barν \to e^+ + e^- $ inside a compact star

We have studied the $ν+ \barν \to e^+ + e^- $ energy deposition rate in a rotating compact star. This reaction is important for the study of gamma ray bursts. The General Relativistic (GR) effects on the energy deposition rate have been incorporated. We find that the efficiency of the process is larger for a rotating star. The total energy deposition rate increases by more than an order of magnitude due to rotation. The dependence of this energy deposition rate on the deformation parameter of the star has also been discussed.

astro-ph↗
arXiv2006

The conversion of Neutron star to Strange star : A two step process

The conversion of neutron matter to strange matter in a neutron star have been studied as a two step process. In the first step, the nuclear matter gets converted to two flavour quark matter. The conversion of two flavour to three flavour strange matter takes place in the second step. The first process is analysed with the help of equations of state and hydrodynamical equations, whereas, in the second process, non-leptonic weak interaction plays the main role. Velocities and the time of travel through the star of these two conversion fronts have been analysed and compared.

astro-ph↗
arXiv2006

Susceptibilities and speed of sound from PNJL model

We present the Taylor expansion coefficients of the pressure in quark number chemical potential $μ_0=μ_B / 3=μ_u=μ_d$, for the strongly interacting matter as described by the PNJL model for two light degenerate flavours of quarks u and d. The expansion has been done upto eighth order in $μ_0$, and the results are consistent with recent estimates from Lattice. We have further obtained the specific heat $C_V$, squared speed of sound $v_s^2$ and the conformal measure $\cC$.

hep-ph↗
arXiv2006

Colour entangled orphan quarks and dark energy from cosmic QCD phase transition

The present day astrophysical observations indicate that the universe is composed of a large amount of dark energy (DE) responsible for an accelerated expansion of the universe, along with a sizeable amount of cold dark matter (CDM), responsible for structure formation. The explanations for the origin or the nature of both CDM and DE seem to require ideas beyond the standard model of elementary particle interactions. Here we show that CDM and DE both can arise from the standard principles of strong interaction physics and quantum entanglement.

hep-ph↗
arXiv2006

QCD phase transition in rotaing neutron star, Neutrino beaming and Gamma-ray bursters

We have studied the emission of neutrinos from a rotating hybrid star. We find that the emission is predominantly confined to a very small angle, provided the core of the star is in a mixed phase of quarks and hadrons and the size of such a mixed phase is small. Annihilation of neutrinos to produce gamma rays has been discussed. The estimated duration of the burst is found to be within the observational range.

astro-ph↗
arXiv2005

Rotating Quark Star in Chiral Colour Dielectric Model

The properties of rotating quark star is studied using the equation of state obtained from Chiral Colour Dielectric model. The results are compared with the MIT bag model results. The frequencies in the corotating innermost circular orbits for different central densities are evaluated and compared with the observational results.

astro-ph↗
arXiv2005

Cosmological dark energy from the cosmic QCD phase transition and colour entanglement

Recent astrophysical observations indicate that the universe is composed of a large amount of dark energy (DE) responsible for an accelerated expansion of the universe, along with a sizeable amount of cold dark matter (CDM), responsible for structure formation. At present, the explanations for the origin or the nature of both CDM and DE seem to require ideas beyond the standard model of elementary particle interactions. Here, for the first time, we show that CDM and DE can arise entirely from the standard principles of strong interaction physics and quantum entanglement. Quantitative agreement with the present data obtains without the need for any adjustable parameters.

hep-ph↗
arXiv2005

Strangeness, Cosmological Cold Dark Matter and Dark Energy

It is now believed that the universe is composed of a small amount of the normal luminous matter, a substantial amount of matter (Cold Dark Matter: CDM) which is non-luminous and a large amount of smooth energy (Dark Energy: DE). Both CDM and DE seem to require ideas beyond the standard model of particle interactions. In this work, we argue that CDM and DE can arise entirely from the standard principles of strong interaction physics out of the same mechanism.

astro-ph↗
arXiv2004

Rotating Twin Stars and Signature of Quark-Hadron Phase Transition

The quark hadron phase transition in a rotating compact star has been studied. The NLZ-model has been used for the hadronic sector and the MIT Bag model has been used for the quark sector. It has been found that rotating twin star (third family) solutions are obtained upto $Ω\approx 4000 s^{-1}$. Stars which are rotating faster than this limit do not show any twin star solution. A backbending in moment of inertia is also observed in the supermassive rest mass sequences. The braking index is found to diverge for a star having pure quark core.

astro-ph↗
arXiv2003

Role of in-medium hadrons in photon-nucleus reactions : shadowing and dilepton spectrum

We study the effect of in-medium hadronic properties in photon nucleus interactions in the context of shadowing as well as the dilepton spectrum for incident photon energies in the range 1.1- 3 GeV. A reasonable agreement with the experimental data for shadowing is obtained in a scenario of downward spectral shift of the hadrons. We show that distinguishable features for in-medium changes of the hadronic properties can be observed experimentally through the dilepton spectrum by judicious choice of target nuclei and incident energy of photons.

nucl-th↗