Thermodynamic and Transport Properties of Matter Formed in $pp$, $p$-Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider using Color String Percolation Model

TL;DR

This study uses the Color String Percolation Model to analyze thermodynamic and transport properties of matter created in various high-energy collisions at the LHC, revealing conditions indicative of quark-gluon plasma formation in high-multiplicity events.

Contribution

It provides new estimates of initial energy density, temperature, and viscosity ratios in different collision systems, highlighting a threshold multiplicity for QGP-like behavior at the LHC.

Findings

High-multiplicity events reach critical energy density and temperature levels.

Estimated shear viscosity to entropy density ratios are comparable to those in heavy-ion collisions.

Indications of a transition in system dynamics at a charged particle multiplicity of around 20.

Abstract

To have a better understanding of the matter formed in ultra-relativistic collisions, using the Color String Percolation Model (CSPM), we have estimated initial energy density, mean free path, squared speed of sound, shear viscosity to entropy density ratio ($\eta/s$), bulk viscosity to entropy density ratio and bulk modulus for $pp$, $p$-Pb, Xe-Xe and Pb-Pb collisions at the Large Hadron Collider (LHC). These observables are studied as a function of final state charged particle multiplicity density and initial state percolation temperature. The results from this work are compared with the results from well known QCD models and with the transport properties of matter found in day-to-day life. These observables allow us to conclude an array of important findings about the matter formed in high energy collisions at the LHC. This work gives a threshold of charged particle multiplicity $\langle dN_{ch}/d\eta \rangle \simeq$ 20, after which there are indications of change in the dynamics of the systems. The critical initial energy density and temperature as estimated by lattice QCD, are observed to be achieved for events with final state multiplicity $\langle dN_{ch}/d\eta \rangle \geq$ 20. In addition, for these high-multiplicity events, the estimated $\eta/s$ are comparable with that is observed for heavy-ion collisions, which is an indication of a strongly coupled Quark Gluon Plasma. This makes LHC high-multiplicity $pp$ collision events as probable candidates for the search of QGP droplets.