Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDe-Confinement and Clustering of Color Sources in Nuclear Collisions
259
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
A brief introduction of the relationship of string percolation to the Quantum Chromo Dynamics (QCD) phase diagram is presented. The behavior of the Polyakov loop close to the critical temperature is studied in terms of the color fields inside the clusters of overlapping strings, which are produced in high energy hadronic collisions. The non-Abelian nature of the color fields implies an enhancement of the transverse momentum and a suppression of the multiplicities relative to the non overlapping case. The prediction of this framework are compared with experimental results from the SPS, RHIC and LHC for $pp$ and AA collisions. Rapidity distributions, probability distributions of transverse momentum and multiplicities, Bose-Einstein correlations, elliptic flow and ridge structures are used to evaluate these comparison. The thermodynamical quantities, the temperature, and energy density derived from RHIC and LHC data and Color String Percolation Model (CSPM) are used to obtain the shear viscosity to entropy density ratio ($eta/s$). It was observed that the inverse of ($eta/s$) represents the trace anomaly $Delta =(varepsilon-3P)/T^{4}$. Thus the percolation approach within CSPM can be successfully used to describe the initial stages in high energy heavy ion collisions in the soft region in high energy heavy ion collisions. The thermodynamical quantities, temperature and the equation of state are in agreement with the lattice QCD calculations. Thus the clustering of color sources has a clear physical basis although it cannot be deduced directly from QCD.
rate research
Read More
It is shown that de-confinement can be achieved in high multiplicity non jet $bar{p}$p collisions at $sqrt{s}$= 1.8 TeV Fermi National Accelerator Laboratory(FNAL- E735) experiment. Previously the evidence for de-confinement was the demonstrated by the constant freeze out energy density in high multiplicity events. In this paper we use the same data but analyze the transverse momentum spectrum in the framework of the clustering of color sources. The charged particle pseudorapidities densities in the range 7.0 $leq langle dN_{c}/deta rangle leq$26.0 are considered. Results are presented for both thermodynamic and transport properties. The initial temperature and energy density are obtained and compared with the Lattice Quantum Chromo Dynamics(LQCD) simulations. The energy density ($varepsilon/T^{4}$) $sim$ 11.5 for $ langle dN_{c}/deta rangle sim $ 25.0 is close to the value for 0-10% central events in Au+Au collisions at $sqrt{s_{NN}}$= 200 GeV. The shear viscosity to entropy density ratio($eta/s$) is $sim$ 0.2 at the transition temperature. The result for the trace anomaly $Delta$ is in excellent agreement with LQCD simulations. These results confirm our earlier observation that the de-confined state of matter was created in high multiplicity events in $bar{p}$p collisions at $sqrt{s}$=1.8 TeV.
In heavy ion collisions, elliptic flow $v_2$ and radial flow, characterized by event-wise average transverse momentum $[p_{mathrm{T}}]$, are related to the shape and size of the overlap region, which are sensitive to the shape of colliding atomic nuclei. The Pearson correlation coefficient between $v_2$ and $[p_{mathrm{T}}]$, $rho_2$, was found to be particularly sensitive to the quadrupole deformation parameter $beta$ that is traditionally measured in low energy experiments. Built on earlier insight that the prolate deformation $beta>0$ reduces the $rho_2$ in ultra-central collisions (UCC), we show that the prolate deformation $beta<0$ enhances the value of $rho_2$. As $beta>0$ and $beta<0$ are the two extremes of triaxiality, the strength and sign of $v_2^2-[p_{mathrm{T}}]$ correlation can be used to provide valuable information on the triaxiality of the nucleus. Our study provide further arguments for using the hydrodynamic flow as a precision tool to directly image the deformation of the atomic nuclei at extremely short time scale ($<10^{-24}$s).
I review the current status and some prospects of theoretical studies on open heavy flavor physics in nuclear collisions at RHIC and LHC energies.
Predictions for the global polarization of $Lambda$ hyperons in Au+Au collisions at moderately relativistic collision energies, 2.4 $leqsqrt{s_{NN}}leq$ 11 GeV, are made. These are based on the thermodynamic approach to the global polarization incorporated into the model of the three-fluid dynamics. Centrality dependence of the polarization is studied. It is predicted that the polarization reaches a maximum or a plateau (depending on the equation of state and centrality) at $sqrt{s_{NN}}approx$ 3 GeV. It is found that the global polarization increases with increasing width of the rapidity window around the midrapidity.
Kaon production in pion-nucleon collisions in nuclear matter is studied in the resonance model. To evaluate the in-medium modification of the reaction amplitude as a function of the baryonic density we introduce relativistic, mean-field potentials for the initial, final and intermediate mesonic and baryonic states. These vector and scalar potentials were calculated using the quark-meson coupling (QMC) model. The in-medium kaon production cross sections in pion-nucleon interactions for reaction channels with $Lambda$ and $Sigma$ hyperons in the final state were calculated at the baryonic densities appropriate to relativistic heavy ion collisions. Contrary to earlier work which has not allowed for the change of the cross section in medium, we find that the data for kaon production are consistent with a repulsive $K^+$-nucleus potential.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
