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, $\frac{dE_{\rm{T}}/d\eta}{dN_{\rm{ch}}/d\eta} ~\equiv \frac{E_{\rm{T}}}{N_{\rm{ch}}}$) 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 $\frac{E_{\rm{T}}}{N_{\rm{ch}}}$.Comment: 19 pages, 7 figure

A new description of transverse momentum spectra of identified particles produced in proton-proton collisions at high energies

The transverse momentum spectra of identified particles produced in high energy proton-proton ($p+p$) collisions are empirically described by a new method with the framework of participant quark model or the multisource model at the quark level, in which the source itself is exactly the participant quark. Each participant (constituent) quark contributes to the transverse momentum spectrum, which is described by the TP-like function, a revised Tsallis--Pareto-type function. The transverse momentum spectrum of the hadron is the convolution of two or more TP-like functions. For a lepton, the transverse momentum spectrum is the convolution of two TP-like functions due to two participant quarks, e.g. projectile and target quarks, taking part in the collisions. A discussed theoretical approach seems to describe the $p+p$ collisions data at center-of-mass energy $\sqrt{s}=200$ GeV, 2.76 TeV, and 13 TeV very well.Comment: 19 pages, 7 figures. Advances in High Energy Physics, accepte

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.Comment: 5 pages, 5 figures, Minor changes in the tex

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.Comment: 9 pages, 17 figure