Jajati K. Nayak

Radial flow from electromagnetic probes and signal of quark gluon plasma

An attempt has been made to extract the evolution of radial flow from the analysis of the experimental data on electromagnetic probes measured at the energies available at the CERN Super Proton Synchrotron (SPS) and the BNL Relativistic Heavy Ion Collider (RHIC). The transverse momentum (

Thermal radiation from Au+Au collisions at GeV energy

{p}_{T}

The “horn” in the kaon-to-pion ratio

) spectra of photons and dileptons measured by the WA98 and NA60 Collaborations, respectively, at the SPS and the photon and dilepton spectra obtained by the PHENIX Collaboration at the RHIC have been used to constrain the theoretical models. We use the ratio of photon to dilepton spectra to extract the flow, where some model dependence is canceled out. Within the ambit of the present analysis we argue that the variation of the radial velocity with invariant mass is indicative of a phase transition from the initially produced partons to hadrons at SPS and RHIC energies.

Two Introductory Lectures on High-Energy QCD and Heavy-Ion Collisions

The transverse momentum distribution of the direct photons measured by the PHENIX Collaboration in Au+Au collisions at GeV/A has been analysed. 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.

Measuring initial temperature through a photon to dilepton ratio in heavy-ion collisions

A microscopic approach has been employed to study the kaon productions in heavy-ion collisions. The momentum-integrated Boltzmann equation has been used to study the evolution of strangeness in the system formed in heavy-ion collisions at relativistic energies. The kaon productions have been calculated for different center-of-mass energies ({radical}(s{sub NN})) ranging from the Alternating Gradient Synchrotron (AGS) to the Relativistic Heavy Ion Collider (RHIC). The results have been compared with available experimental data. We obtain a nonmonotonic hornlike structure for K{sup +}/{pi}{sup +} when plotted with {radical}(s{sub NN}) with the assumption of an initial partonic phase beyond a certain threshold in {radical}(s{sub NN}). However, a monotonic rise of K{sup +}/{pi}{sup +} is observed when a hadronic initial state is assumed for all {radical}(s{sub NN}). Experimental values of K{sup -}/{pi}{sup -} are also reproduced within the ambit of the same formalism. Results from scenarios where the strange quarks and hadrons are formed in equilibrium and evolve with and without secondary productions have also been presented.

Do the pp Collisions at LHC Energies Form a Collective Medium

These introductory lectures present a broad overview of the physics of high parton densities in QCD and its application to our understanding of the early time dynamics in heavy-ion collisions.

Strange Hyperon Productions at LHC Energies

Theoretical calculation of transverse momentum (pT) 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 pT spectra of thermal photons to lepton pairs has been evaluated and it is shown that the ratio is insensitive to some of these parameters.

Kaon and Lambda productions in relativistic heavy ion collisions

Whether the relativistic pp collisions at LHC energies serve as the base line for the analysis of heavy ion collisions or they produce a medium like heavy ion collisions is a matter of intense debate. In this work, we analyze the charged hadron spectra produced from pp collisions at \(\sqrt{s_{NN}}=7\) TeV, LHC energy on the basis of hydrodynamical model to address the issue of collectivity and medium formation. The spectra of identified particles (\(\pi , K, p\)) have been evaluated for different mean multiplicities and compared with the data [1] measured by CMS collaboration. It has been found that \(\pi , K\) spectra obtained from high multiplicity events are explained reasonably well for an initial energy density \(\varepsilon _i \ge 1.5\) GeV/fm\(^3\).

Muon pairs from In + In collision at energies available at the CERN Super Proton Synchrotron

Strange hadrons act as good probe to determine the nature of the medium formed in heavy ion collisions. We study the production of strange hyperons \(\varLambda \) and \(\Sigma \) using momentum integrated Boltzmann transport equation at FAIR and LHC energies (4.54 GeV, 2.76 and 7 TeV). We also investigate the production of multi strange hyperon \(\Xi \) using the same model.

Indication of transverse radial flow in high-multiplicity proton–proton collisions at the Large Hadron Collider

Abstract A microscopic approach has been employed to study the kaon and Λ productions in heavy ion collisions. The productions of K + and Λ have been studied within the framework of Boltzmann transport equation for various beam energies. We find a non-monotonic horn like structure for K + / p i + and Λ / π when plotted against centre of mass energies ( s N N ) with the assumption of initial partonic phase for s N N shows a monotonic nature when a hadronic initial state is considered for all s N N . Experimental values of K − / π − for different s N N are also reproduced within the ambit of the same formalism.