Event topology and global observables in heavy-ion collisions at the Large Hadron Collider

Suraj Prasad,Debadatta Behera,Neelkamal Mallick,Raghunath Sahoo,Sushanta Tripathy

doi:10.1038/s41598-022-07547-z

Abstract

Particle production and event topology are very strongly correlated in high-energy hadronic and nuclear collisions. Event topology is decided by the underlying particle production dynamics and medium effects. Transverse spherocity is an event shape observable, which has been used in pp and heavy-ion collisions to separate the events based on their geometrical shapes. It has the unique capability to distinguish between jetty and isotropic events. In this work, we have implemented transverse spherocity in Pb–Pb collisions at sqrt{s_text{NN}} = 5.02 TeV using A Multi-Phase Transport Model (AMPT). While awaiting for experimental explorations, we perform a feasibility study of transverse spherocity dependence of some of the global observables in heavy-ion collisions at the Large Hadron Collider energies. These global observables include the Bjorken energy density (varepsilon _text{Bj}), squared speed of sound (c_text{s}^2) in the medium and the kinetic freeze-out properties for different collision centralities. The present study reveals about the usefulness of event topology dependent measurements in heavy-ion collisions.

Highlights

The present study reveals about the usefulness of event topology dependent measurements in heavy-ion collisions
The spherocity distributions in Pb–Pb collisions look shifted more towards the isotropic limit when compared to the pp collisions, where the distributions are shifted towards the jetty limit
This behavior is understood based on the fact that the system size in Pb–Pb collisions are significantly higher when compared with pp collisions and the medium effect in terms of rescattering helps taking the system towards isotropisation

Summary

Introduction

These global observables include the Bjorken energy density ( εBj ), squared speed of sound ( cs2 ) in the medium and the kinetic freeze-out properties for different collision centralities. In elementary and hadronic collisions at GeV and TeV energies, event topology dependent studies have got some level of importance, because of a dense medium formation in heavy-ion collisions, these techniques like sphericity, transverse spherocity, RT etc.

Results

Conclusion