arXiv subjects

Raghunath Sahoo

Publications and source records attributed to Raghunath Sahoo.

160 records · Page 9Linked to original sources

arXiv2016

Evolution of Temperature Fluctuation in a Thermal bath and, its implications in Hadronic and Heavy-Ion Collisions

The evolution equation for inhomogeneous and anisotropic temperature fluctuations inside a medium is derived within the ambit of Boltzmann Transport Equation. Also, taking some existing realistic inputs we have analyzed the Fourier space variation of temperature fluctuation for the medium created after heavy-ion collisions. The effect of viscosity on the variation of fluctuations is investigated. Further, possible implications in hadronic and heavy-ion collisions are explored.

hep-ph↗

arXiv2016

The q-Statistics and QCD Thermodynamics at LHC

We perform a Taylor series expansion of Tsallis distribution by assuming the Tsallis parameter $q$ close to 1. The $q$ value shows the deviation of a system from a thermalised Boltzmann distribution. By taking up to first order in $(q-1)$, we derive an analytical result for Tsallis distribution including radial flow. Further, in the present work, we also study the speed of sound ($c_s$) as a function of temperature using the non-extensive Tsallis statistics for different $q$ values and for different mass cut-offs.

hep-ph↗

arXiv2016

Radial Flow in Non-Extensive Thermodynamics and Study of Particle Spectra at LHC in the Limit of Small $(q-1)$

We expand the Tsallis distribution in a Taylor series of powers of (q-1), where q is the Tsallis parameter, assuming q is very close to 1. This helps in studying the degree of deviation of transverse momentum spectra and other thermodynamic quantities from a thermalized Boltzmann distribution. After checking thermodynamic consistency, we provide analytical results for the Tsallis distribution in the presence of collective flow up to the first order of (q-1). The formulae are compared with the experimental data.

hep-ph↗

arXiv2015

Time Evolution of Temperature Fluctuation in a Non-Equilibrated System

The evolution equation for inhomogeneous and anisotropic temperature fluctuation inside a medium is derived within the ambit of Boltzmann Transport Equation (BTE) for a hot gas of massless particles. Also, specializing to a situation created after heavy-ion collision (HIC), we analyze the Fourier space variation of temperature fluctuation of the medium using its temperature profile. The effect of viscosity on the variation of fluctuations in the latter case is investigated and possible implications for early universe cosmology, and its connection with HICs are also explored.

hep-ph↗

arXiv2015

Multiparticle production in nuclear collisions using effective-energy approach

The dependencies of charged particle pseudorapidity density and transverse energy pseudorapidity density at midrapidity on the collision energy and on the number of nucleon participants, or centrality, measured in nucleus-nucleus collisions are studied in the energy range spanning a few GeV to a few TeV per nucleon. The study is based on the earlier proposed model, combining the constituent quark picture together with Landau relativistic hydrodynamics and shown to interrelate the measurements from different types of collisions. Within this picture, the dependence on the number of participants in heavy-ion collisions are found to be well described in terms of the effective energy defined as a centrality-dependent fraction of the collision energy. The effective energy approach is shown to reveal a similarity in the energy dependence for the most central and centrality data in the entire available energy range. Predictions are made for the forthcoming higher-energy measurements in heavy-ion collisions at the LHC.

hep-ph↗

arXiv2014

Effective-energy budget in multiparticle production in nuclear collisions

The dependencies of charged particle pseudorapidity density and transverse energy pseudorapidity density at midrapidity on the collision energy and on the number of nucleon participants, or centrality, measured in nucleus-nucleus collisions are studied in the energy range spanning a few GeV to a few TeV per nucleon. The model in which the multiparticle production is driven by the dissipating effective energy of participants is introduced. The model is based on the earlier proposed approach, combining the constituent quark picture together with Landau relativistic hydrodynamics shown to interrelate the measurements from different types of collisions. Within this model, the dependence on the number of participants in heavy-ion collisions are found to be well described in terms of the effective energy defined as a centrality-dependent fraction of the collision energy. For both variables under study, the effective energy approach reveals a similarity in the energy dependence obtained for the most central collisions and centrality data in the entire available energy range. Predictions are made for the investigated dependencies for the forthcoming higher energy measurements in heavy-ion collisions at the LHC.

nucl-th↗

arXiv2014

Charged Particle and Photon Multiplicity, and Transverse Energy Production in High-Energy Heavy-Ion Collisions

We review the charged particle and photon multiplicity, and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons and the transverse energy measurement.

nucl-ex↗

arXiv2014

Transverse energy and charged particle production in heavy-ion collisions: From RHIC to LHC

We study the charged particle and transverse energy production mechanism from AGS, SPS, RHIC to LHC energies in the framework of nucleon and quark participants. At RHIC and LHC energies, the number of nucleons-normalized charged particle and transverse energy density in pseudorapidity, which shows a monotonic rise with centrality, turns out to be an almost centrality independent scaling behaviour when normalized to the number of participant quarks. A universal function which is a combination of logarithmic and power-law, describes well the charged particle and transverse energy production both at nucleon and quark participant level for the whole range of collision energies. Energy dependent production mechanisms are discussed both for nucleonic and partonic level. Predictions are made for the pseudorapidity densities of transverse energy, charged particle multiplicity and their ratio (the barometric observable, $\frac{dE_{\rm{T}}/dη}{dN_{\rm{ch}}/dη} ~\equiv \frac{E_{\rm{T}}}{N_{\rm{ch}}}$) at mid-rapidity for Pb+Pb collisions at $\sqrt{s_{\rm{NN}}}=5.5$ TeV. A comparison with models based on gluon saturation and statistical hadron gas is made for the energy dependence of $\frac{E_{\rm{T}}}{N_{\rm{ch}}}$.

hep-ph↗

arXiv2013

Constituent Quark Scaling of Strangeness Enhancement in Heavy-Ion Collisions

In the frame work of a nuclear overlap model, we estimate the number of nucleon and quark participants in proton-proton, proton-nucleus and nucleus-nucleus collisions. We observe the number of nucleon ($N_{N-part}$)-normalized enhancement of multi-strange particles which show a monotonic increase with centrality, turns out to be a centrality independent scaling behavior when normalized to number of constituent quarks participating in the collision ($N_{q-part}$). In addition, we observe that the $N_{q-part}$-normalized enhancement, when further normalized to the strangeness content, shows a strangeness independent scaling behavior. This holds good at top RHIC energy. However, the corresponding SPS data show a weak $N_{q-part}$-scaling with strangeness scaling being violated at top SPS energy. This scaling at RHIC indicates that the partonic degrees of freedom playing an important role in the production of multi-strange particles. Top SPS energy, in view of the above observations, shows a co-existence of hadronic and partonic phases. We give a comparison of data with HIJING, AMPT and UrQMD models to understand the particle production dynamics at different energies.

hep-ph↗

arXiv2011

Probing the QGP Phase Boundary with Thermal Properties of $ϕ$ Mesons

A novel attempt has been made to probe the QCD phase boundary by using the experimental data for transverse momenta of ϕ mesons produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted with simple thermodynamic expectations and lattice QCD results. The experimental data indicate a first-order phase transition, with a mixed phase stretching the energy density between \sim1 and 3.2 GeV/fm3 corresponding to SPS energies.

nucl-ex↗

arXiv2009

$ϕ$ Meson As a Probe of QCD Equation of State

In this work, we extract the QCD Equation of State (EoS) using experimental results of the $ϕ$ meson produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted to simple thermodynamic expectations and lattice results. The experimental data indicate a first order phase transition, with a mixed phase stretching energy density between $\sim$ 1 and 3.2 GeV/$fm^3$.

hep-ph↗

arXiv2009

The QCD Equation of State with Thermal Properties of $ϕ$ mesons

In this work a first attempt is made to extract the Equation of State (EoS) using experimental results of the $ϕ$ meson produced in nuclear collisions at AGS, SPS and RHIC energies. The data are confronted to simple thermodynamic expectations and lattice results. The experimental data indicate a first order phase transition, with a mixed phase stretching energy density between $\sim$ 1 and 3.2 GeV/$fm^3$.

nucl-ex↗

arXiv2008

Global Properties of Nucleus-Nucleus Collisions

In this lecture note, we discuss the global properties of nucleus-nucleus collisions. After a brief introduction to heavy-ion collisions, we introduce useful kinematics and then discuss the bulk hadron production in A+A collisions. At the end we discuss the hadronization and hadronic freeze-out in A+A collisions. We have tried to cover the topic from very fundamental arguments especially for the beginners in the field. We also give very useful formulae frequently used by experimentalists, from a first principle derivation.

nucl-ex↗

arXiv2008

Transverse Energy Measurement in Au+Au Collisions by the STAR Experiment

Transverse energy ($E_T$) has been measured with both of its components, namely hadronic ($E_T^{had}$) and electromagnetic ($E_T^{em}$) in a common phase space at mid-rapidity for 62.4 GeV Au+Au collisions by the STAR experiment. $E_T$ production with centrality and $\sqrt{s_{NN}}$ is studied with similar measurements from SPS to RHIC and is compared with a final state gluon saturation model (EKRT). The most striking feature is the observation of a nearly constant value of $E_T/N_{ch} \sim 0.8$ GeV from AGS, SPS to RHIC. The initial energy density estimated by the boost-invariant Bjorken hydrodynamic model, is well above the critical density for a deconfined matter of quarks and gluons predicted by lattice QCD calculations.

nucl-ex↗

arXiv2008

Transverse Energy Measurement and Fluctuation Studies in Ultra-Relativistic Heavy Ion Collisions

Transverse energy ($E_T$) has been measured with both of it's components, namely hadronic ($E_T^{had}$) and electromagnetic ($E_T^{em}$) at mid-rapidity, for 62.4 GeV Au+Au collisions by the STAR experiment. In the common phase space of TPC and BEMC ($0 < η< 1$ and full $ϕ$), we have obtained $E_T^{had}$ from the TPC reconstructed tracks and $E_T^{em}$ from the BEMC tower hits after correcting for the hadronic contaminations in the calorimeter. The centrality behavior of $ /(0.5 N_{part})$ and the excitation function of $ /(0.5 N_{part})$ has been compared with the final state gluon saturation model (EKRT) along with similar measurements from SPS to RHIC. The most striking feature is the observation of a nearly constant value of $E_T/N_{ch} \sim 0.8$ GeV from AGS, SPS to RHIC. The $E_T$ and $N_{ch}$ production has been observed to follow a logarithmic behavior. The initial energy density estimated by the boost-invariant Bjorken hydrodynamic model, is well above the lattice QCD value for a deconfined matter of Quarks and Gluons. Taking similar colliding species i.e. Au+Au, the $ε_{Bj} .τ$ has been predicted for LHC, based on the measurements at RHIC. We have also made predictions for $(dE_T/dη)/(0.5 N_{part})$ and $(dN_{ch}/dη)/(0.5 N_{part})$ for the LHC energy. Furthermore, we have studied the event-by event fluctuations in $E_T$ and in the ratio of it's components using $σ/μ$ as the fluctuation observable.

nucl-ex↗

arXiv2005

Transverse energy measurement in sqrt{s_{NN}} = 62.4 GeV Au+Au collisions at RHIC

The transverse energy distributions ($E_{T}$) have been measured for Au + Au collisions at $\sqrt{s_{NN}} = 62.4$ GeV by the STAR experiment at RHIC. They have been obtained from two measurements, the hadronic transverse energy ($E_{T}^{had}$) and the electromagnetic transverse energy($E_{T}^{em}$). $E_{T}^{had}$ has been measured from the tracks obtained by Time Projection Chamber (TPC) excluding the electrons and positrons. $E_{T}^{em}$ has been obtained by the STAR Barrel Electromagetic Calorimeter (BEMC) which measures the energy of electrons, positrons and photons. The measure of transverse energy gives an estimate of the energy density of the fireball produced in heavy ion collisions. $E_{T}$ per participant pair gives information about the production mechanism of particles.

nucl-ex↗