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Register a new userElliptic Flow in Pb+Pb Collisions at $sqrt{s_{rm NN}}$ = 2.76 TeV at the LHC Using Boltzmann Transport Equation with Non-extensive Statistics
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Elliptic flow in heavy-ion collisions is an important signature of a possible de-confinement transition from hadronic phase to partonic phase. In the present work, we use non-extensive statistics, which has been used for transverse momentum ($p_{rm T}$) distribution in proton+proton ($p+p$) collisions, as the initial particle distribution function in Boltzmann Transport Equation (BTE). A Boltzmann-Gibbs Blast Wave (BGBW) function is taken as an equilibrium function to get the final distribution to describe the particle production in heavy-ion collisions. In this formalism, we try to estimate the elliptic flow in Pb+Pb collisions at $sqrt{s_{rm NN}}$ = 2.76 TeV at the LHC for different centralities. The elliptic flow ($v_2$) of identified particles seems to be described quite well in the available $p_{rm T}$ range. An approach, which combines the non-extensive nature of particle production in $p+p$ collisions through an evolution in kinetic theory using BTE, with BGBW equilibrium distribution is successful in describing the spectra and elliptic flow in heavy-ion collisions.
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Elliptic flow of hadrons observed at relativistic heavy-ion collision experiments at Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC), provides us an important signature of possible de-confinement transition from hadronic phase to partonic phase. However, hadronization processes of de-confined partons back into final hadrons are found to play a vital role in the observed hadronic flow. In the present work, we use coalescence mechanism also known as Recombination (ReCo) to combine quarks into hadrons. To get there, we have used Boltzmann transport equation in relaxation time approximation to transport the quarks into equilibration and finally to freeze-out surface, before coalescence takes place. A Boltzmann-Gibbs Blast Wave (BGBW) function is taken as an equilibrium function to get the final distribution and a power-like function to describe the initial distributions of partons produced in heavy-ion collisions. In the present work, we try to estimate the elliptic flow of identified hadrons such as $pi$, $K$, $p$ etc., produced in Pb+Pb collisions at $sqrt{s_{rm NN}}$ = 2.76 TeV at the LHC for different centralities. The elliptic flow ($v_2$) of identified hadrons seems to be described quite well in the available $p_{rm T}$ range. After the evolution of quarks until freeze-out time, has been calculated using BTE-RTA, the approach used in this paper consists of combining two or more quarks to explain the produced hadrons at intermediate momenta regions. The formalism is found to describe elliptic flow of hadrons produced in Pb+Pb collisions to a large extent.
In the continuation of our previous work, the transverse momentum ($p_T$) spectra and nuclear modification factor ($R_{AA}$) are derived using relaxation time approximation of Boltzmann Transport Equation (BTE). The initial $p_T$-distribution used to describe $p+p$ collisions has been studied with the pQCD inspired power-law distribution, the Hagedorns empirical formula and with the Tsallis non-extensive statistical distribution. The non-extensive Tsallis distribution is observed to describe the complete range of the transverse momentum spectra. The Boltzmann-Gibbs Blast Wave (BGBW) distribution is used as the equilibrium distribution in the present formalism, to describe the $p_T$-distribution and nuclear modification factor in nucleus-nucleus collisions. The experimental data for Pb+Pb collisions at $sqrt{s_{NN}}$ = 2.76 TeV at the Large Hadron Collider at CERN have been analyzed for pions, kaons, protons, $K^{*0}$ and $phi$. It is observed that the present formalism while explaining the transverse momentum spectra upto 5 GeV/c, explains the nuclear modification factor very well upto 8 GeV/c in $p_T$ for all these particles except for protons. $R_{AA}$ is found to be independent of the degree of non-extensivity, $q_{pp}$ after $p_T sim$ 8 GeV/c.
The nuclear modification factors ($R_{AA}$) of $pi^{pm}, p(bar p)$, and $d(bar d)$ with $|y|<0.5, p_T<20.0$~GeV/c in peripheral (40-60%) and central (0-5%) Pb-Pb collisions at $sqrt {s_{NN}}=2.76$ TeV have been studied using the parton and hadron cascade ({footnotesize PACIAE}) model plus the dynamically constrained phase space coalescence ({footnotesize DCPC}) model. It is found that the $R_{AA}$ of light (anti)nuclei ($d, bar d$) is similar to that of hadrons ($pi^pm, p, bar p$), and the $R_{AA}$ of antiparticles is the same as that of particles. The suppression of $R_{AA}$ at high-$p_T$ strongly depends on event centrality and mass of the particles, i.e., the central collision is more suppressed than the peripheral collision. Besides, the yield ratios and double ratios for different particle species in $pp$ and Pb-Pb collisions are discussed, respectively. It is observed that the yield ratios and double ratios of $d$ to $p$ and $p$ to $pi$ are similar to those of their anti-particles in three different collision systems, suggesting that the suppressions of matter ($pi^{+}, p, d$) and the corresponding antimatter ($pi^{-},bar{p},bar{d}$) are around the same level.
A simple approach based on the separation of wounded nucleons in an A-A collision in two categories, those suffering single collisions - corona and the rest - core, estimated within a Glauber Monte-Carlo approach, explains the centrality dependence of the light flavor hadrons production in Pb-Pb collisions at $sqrt{s_{NN}}$=2.76 TeV. The core contribution does not include any dependence of any process on the fireball shape as a function of the impact parameter. Therefore, the ratios of the $p_T$ distributions to the one corresponding to the minimum bias pp collisions at the same energy, each of them normalised to the corresponding charged particle density, the $langle p_Trangle$ and transverse energy per unit of rapidity are reproduced less accurate by such an approach. The results show that the corona contribution plays an important role also at LHC energies and it has to be considered in order to evidence the centrality dependence of different observables related to the core properties and dynamics.
We analyze the elliptic flow parameter v_2 in Pb+Pb collisions at sqrt{s_{NN}} = 2.76 TeV and in Au+Au collisions at sqrt{s_{NN}} =200 GeV using a hybrid model in which the evolution of the quark gluon plasma is described by ideal hydrodynamics with a state-of-the-art lattice QCD equation of state, and the subsequent hadronic stage by a hadron cascade model. For initial conditions, we employ Monte-Car
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