arXiv subjects

Bikash Sinha

Publications and source records attributed to Bikash Sinha.

At least 19 recordsLinked to original sources

arXiv2020

White holes, primordial black holes and Dark Matter

Strange Quark Nuggets are the relics of the microsecond old universe after the big bang. The universe having experienced a mini inflation of 7-e folding has gone through supercooling leading to a first order phase transition from quark to hadrons. Strange Quark Nuggets, the relics of this phase transition will constitute 12.5% or at the most 25% of the dark matter of the universe. Only 10-3 or 10-4 part of the total number of SQNs form binaries, and only some of the binaries will turn to black holes. Primordial Black Hole (PBH) as a relic is shown to be not a plausible scenario. Simultaneous observation of high energy gamma rays from SQN binaries formed from coalescence of SQNs along with black holes will be the vital cursor of this evolutionary scenario just presented.

physics.gen-ph↗

arXiv2019

Hawking--Unruh Radiation from the relics of the cosmic quark hadron phase transition

It is entirely plausible that during the primordial quark-hadron transition, microseconds after the Big Bang, the universe may experience supercooling accompanied by mini inflation leading to a first-order phase transition from quarks to hadrons. The relics, in the form of quark nuggets expected to consist of Strange Quark Matter, with a baryon number beyond a critical value will survive. It is conjectured that color confinement turns the physical vacuum to an event horizon for quarks and gluons. The horizon can be crossed only by quantum tunnelling. The process just mentioned is the QCD counterpart of Hawking radiation from gravitational black holes. Thus, when the Hawking temperature of the quark nuggets gets turned off, tunnelling will stop and the nuggets will survive forever. The baryon number and the mass of these nuggets are derived using this theoretical format. The results agree well with the prediction using other phenomenological models. Further, the variation of Hawking temperature as a function of baryon number and mass of the nugget mimicks chiral phase transition, somewhat similar to the QCD phase transition just described. Finally the strange quark nuggets may well be the candidates of baryonic dark matter.

physics.gen-ph↗

arXiv2017

The Cosmic Quarks

There are at least three sources of cosmic quarks in the universe. One, the quark nuggets which may survive beyond a certain baryon number during the phase transition from quarks to hadrons microseconds after the big bang. These quark nuggets can very well be candidate of cold dark matter and these nuggets consist of strange quarks. Second, the interior of the neutron star may well be made of quarks due to very very high pressure. It is further shown that the interior of heavy neutron star, recently discovered $\approx$ 2M$_{\odot}$, with an appropriate equation of state, can also be made of quark core. Finally, using the property of colour entanglement among quarks it is entirely possible to have free orphan quarks roaming around in the cosmos. Some better understanding of dark energy and dark matter is possible with these entangled orphan quarks.

physics.gen-ph↗

arXiv2015

Glueballs amass at RHIC and LHC Colliders! - The early quarkless 1st order phase transition at $T=270$ MeV - from pure Yang-Mills glue plasma to GlueBall-Hagedorn states

The early stage of high multiplicity pp, pA and AA collider is represented by a nearly quarkless, hot, deconfined pure gluon plasma. According to pure Yang-Mills Lattice Gauge Theory, this hot pure glue matter undergoes, at a high temperature, $T_c = 270$ MeV, a first order phase transition into a confined Hagedorn-GlueBall fluid. These new scenario should be characterized by a suppression of high $p_T$ photons and dileptons, baryon suppression and enhanced strange meson production. We propose to observe this newly predicted class of events at LHC and RHIC.

hep-ph↗

arXiv2015

On the Quest for Standard Model Cold Dark Matter

The possibility that the relics of quark hadron phase transition in the microsecond old universe, the quark nuggets, may well be reasonable candidates for cold dark matter is critically examined.

physics.gen-ph↗

arXiv2014

Cosmic Separation of Phases: the microsecond universe and the neutron star

It is entirely plausible under reasonable condition, that a first order QCD phase transition occurred from quarks to hadrons when the universe was about a microsecond old. Relics, if there be any, after the quark hadron phase transition are the most deciding signatures of the phase transition. It is shown in this paper that the quark nuggets, possible relics of first order QCD phase transitions with baryon number larger than $10^{43}$ will survive the entire history of the universe uptil now and can be considered as candidates for the cold dark matter. The spin down core of the neutron star on the high density low temperature end of the phase diagramme initiates transition from hadrons to quarks. As the star spins down, the size of the core goes on increasing. Recently discovered massive Pulsar PSRJ 1614-2230 with a mass of 1.97$\pm$0.04 $M_{\odot}$ most likely has a strongly interacting quark core. What possible observables can there be from these neutron stars?

nucl-th↗

arXiv2012

Electromagnetic signals from Au+Au collisions at RHIC energy, $\sqrt{s_{NN}}$=200 GeV and Pb+Pb collisions at LHC energy, $\sqrt{s_{NN}}$=2.76 TeV

We analyse the recently available experimental data on direct photon productions from Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV RHIC and from Pb+Pb collisions at $\sqrt{s_{NN}}$=2.76 TeV LHC energies. The transverse momentum ($p_T$) distributions have been evaluated with the assumption of an initial quark gluon plasma phase at temperatures $T_i$=404 and 546 MeV with initial thermalisation times $τ_i$=0.2 and 0.1 fm/c respectively for RHIC and LHC energies. The theoretical evalutions agree reasonably well with the experimental observations. The thermal window for the LHC energy is justified through the ratio of the $p_T$ spectra of thermal photons to dileptons.

nucl-th↗

arXiv2012

Dilepton to photon ratio, a viscometer of QGP

In the Israel-Stewart's 2nd order hydrodynamics, a viscous effect on dilepton emission from a QGP medium is investigated. Dileptons are strongly affected by QGP viscosity. Large invariant mass dileptons, due to their lower velocity, are less affected by viscosity than the low invariant mass dileptons. We also show that the ratio of photon to dilepton is sensitive to the viscosity and can serve as a viscometer for QGP.

nucl-th↗

arXiv2011

Muon pairs from In+In collision at SPS energy

NA60 collaboration has extracted the inverse slope parameters, T_{eff} of the dimuon spectra originating from the In+In collisions at root(s_NN)=17.3 GeV for various invariant mass region. They have observed that the inverse slope parameter as a function of invariant mass of the lepton pair drops beyond the rho-peak. In the present work, first we reproduce the observed invariant mass and transverse momentum spectra of the muon pairs. Then show that the slope parameters extracted from the transverse momentum distributions for various invariant mass region windows can be explained by assuming formation of a partonic phase initially which reverts to hadronic phase through a weak first order phase transition at a temperature T_c ~ 175 MeV. It is observed that a scenario without the formation of a partonic phase does not reproduce the non-monotonic behaviour of the inverse slope parameter non typical of radial flow.

nucl-th↗

arXiv2011

Direct photon production from viscous QGP

We simulate direct photon production in evolution of viscous QGP medium. Photons from Compton and annihilation processes are considered. Viscous effect on photon production is very strong and reliable simulation is possible only in a limited $p_T$ range. For minimally viscous fluid $η/s$=0.08), direct photons can be reliably computed only up to $p_T \leq$ 1.3 GeV. With reduced viscosity ($η/s$=0.04), the limit increases to $p_T \leq $2GeV.

nucl-th↗

arXiv2010

Nuclear suppression at low energy heavy ion collisions

The effects of non-zero baryonic chemical potential on the drag and diffusion coefficients of heavy quarks propagating through a baryon rich quark gluon plasma have been studied. The nuclear suppression factor, $R_{\mathrm AA}$ for non-photonic single electron spectra resulting from the semileptonic decays of hadrons containing heavy flavours have been evaluated for low energy collisions. The role of non-zero baryonic chemical potential on $R_{\mathrm AA}$ has been highlighted.

nucl-th↗

arXiv2009

Search and study of Quark Gluon Plasma at the CERN-LHC

The major aim of nucleus-nucleus collisions at the LHC is to study the physics of strongly interacting matter and the quark gluon plasma (QGP), formed in extreme conditions of temperature and energy density. We give a brief overview of the experimental program and discuss the signatures and observables for a detailed study of QGP matter.

nucl-ex↗

arXiv2009

Thermal photon to dilepton ratio in ultra-relativistic heavy ion collisions

The ratio of transverse momentum distribution of thermal photons to dilepton has been evaluated. It is observed that this ratio reaches a plateau beyond a certain value of transverse momentum. We argue that this ratio can be used to estimate the initial temperature of the system by selecting the transverse momentum and invariance mass windows judiciously. It is demonstrated that if the radial flow is large then the plateau disappear and hence a deviation from the plateau can be used as an indicator of large radial flow. The sensitivity of the results on various input parameters has been studied.

nucl-th↗

arXiv2008

Measuring initial temperature through photon to dilepton ratio in heavy ion collision

Theoretical calculation of transverse momentum($p_T$) distribution of thermal photons and dileptons originating from ultra-relativistic heavy ion collisions suffer from several uncertainties since the evaluation of these spectra needs various inputs which are not yet known unambiguously. In the present work the ratio of the $p_T$ spectra of thermal photons to lepton pairs has been evaluated and it is shown that the ratio is insensitive to some of these parameters.

nucl-th↗

arXiv2007

Thermal photons to dileptons ratio at LHC

It is shown that the ratio of transverse momentum (p_T) distribution of thermal photons to dileptons produced in heavy ion collisions reaches a plateau above p_T=1 GeV. We argue that the value of the ratio in the plateau region can be used to estimate the initial temperature.

nucl-th↗

arXiv2007

Thermal Radiation from Au + Au Collisions at \sqrt{s} = 200 GEV/A Energy

The transverse momentum distribution of the direct photons measured by the PHENIX collaboration in $Au + Au$ collisions at $\sqrt{s}=200$ GeV/A has been analyzed. It has been shown that the data can be reproduced reasonably well assuming a deconfined state of thermalized quarks and gluons with initial temperature more than the transition temperature for deconfinement inferred from lattice QCD. The value of the initial temperature depends on the equation of state of the evolving matter. The sensitivities of the results on various input parameters have been studied. The effects of the modifications of hadronic properties at non-zero temperature have been discussed.

nucl-th↗

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↗

arXiv2005

Stopping power of hot QCD plasma

The partonic energy loss has been calculated taking both the hard and soft contributions for all the $2 \to 2$ processes, revealing the importance of the individual channels. Cancellation of the intermediate separation scale has been exhibited. Subtleties related to the identical final state partons have properly been taken into account. The estimated collisional loss is compared with its radiative counter part. We show that there exists a critical energy ($E_c$) below which the collisional loss is more than its radiative counterpart. In addition, we present closed form formulas for both the collision probabilities and the stopping power ($dE/dx$)

hep-ph↗