String percolation in AA and p+p collisions

Abstract

A brief review of the string percolation model and its results are presented together with the comparison to experimental data. First, it is done an introduction to the quark-gluon phase diagram and the lattice results concerning the connement and the percolation of center domains. It is studied the interaction of the strings produced in nucleus-nucleus and proton-proton collisions showing how the string percolation arises. The main consequences of the string percolation, concerning the dependence on the energy and centrality, on the multiplicities and the mean transverse momentum are obtained comparing with experimental data. It is emphasized the non-abelian character of the color eld of the strings forming the cluster to reproduce the rise of the transverse momentum with multiplicity and the relative suppression of multiplicities. It is also studied dierent observables like multiplicity and transverse momentum distributions, dependence with multiplicity and transverse momentum correlations, forward-backward correlations, the strength of the Bose-Einstein correlations, dependence on the multiplicity of J/ψ production and its possible suppression in pp collisions at high multiplicity, strangeness enhancement, elliptic ow, and ridge structure. The comparison with the data shows an overall agreement. The thermodynamical properties of the extended cluster formed in the collision are discussed computingits energy and entropy density, shear viscosity over entropy density ratio, bulk viscosity, sound speed and trace anomaly as a function of temperature, showing a remarkable agreement with lattice QCD evaluations. The string percolation can be regarded as the initial frame able to describe the collective behavior produced in AA and pp collisions.

Bose-Einstein condensation and non-extensive statistics

“…We analyzed the variance of the number of particles. The possibility of formation of a condesnate phase in the hadronic systems have been postulated in several works [24,[31][32][33]. Investigations on the High Energy Physics distributions show that, for hadronic systems, q ∼ 1.14, in good agreement with the theoretical prediction [8,9].…”

Tsallis statistics and thermofractals: applications to high energy and hadron physics

“…Refs. [40,41,42]. While the BEC has been exhaustively studied under the light of BG statistics, the same does not hold for Tsallis statistics.…”

Percolation leads to finite-size effects on the transition temperature and center-of-mass energy required for quark-gluon plasma formation

“…In high energy physics, multiparticle production is usually described in terms of color strings stretched between the projectile and target, which decay into new strings through color neutral q q pairs production and subsequently hadronize to produce the observed hadrons [1,2]. Color strings may be viewed as small circular areas distributed in the transverse plane (of the collision) filled with a color field created by colliding partons that interact when they overlap.…”

“…with φ(η) being the area covered by strings and η = N S 1 /S the filling factor, where N is the total number of strings distributed on the transverse plane with area S [1,2]. In particular, for the case of uniformly distributed disks, this picture corresponds to the classical two dimensional continuum percolation of disks, and φ(η) = 1−e −η in the thermodynamic limit [1,12].…”