Anomalous features of particle production in high-multiplicity events of pp collisions at the LHC energies

Samrangy Sadhu,Premomoy Ghosh

doi:10.1103/physrevd.99.034020

Abstract

Prevalent models of multiparticle production in relativistic $pp$ collisions at pre-LHC energies fail to provide convincing explanations of certain significant features of the final-state charged particles in high-multiplicity $pp$ events at the LHC. In this article we study these features---which are usually interpreted as the collective behavior of particle production in relativistic heavy-ion collisions---in the framework of the hydrodynamic epos3 model, emphasizing a quantitative comparison between the data and model-based simulations in the same kinematic ranges for better understanding of the data. The work reveals a quantitative mismatch between the data and the model.

Highlights

The experiments at the Relativistic Heavy Ion Collider (RHIC), through satisfactory descriptions of the flow-like behavior of particle production in relativistic heavy-ion collisions by relativistic hydrodynamics [1], established [2,3,4,5] the formation of a collective medium in such collisions
The suppression of high-pT particles, revealed in terms of the relative yield of charged particles in heavyion collisions compared to pp collisions at the same centerof mass energy, identified the collective medium as a thermalized medium of quark-gluon plasma (QGP) [6,7]
Hadron Collider (LHC) reported flow-like features of particle production in high-multiplicity events of pp collisions, in contrast to the present understanding of particle production in relativistic pp collisions based on the data from the pre-LargeHadron Collider (LHC) energy range

Summary

INTRODUCTION

The experiments at the Relativistic Heavy Ion Collider (RHIC), through satisfactory descriptions of the flow-like behavior of particle production in relativistic heavy-ion collisions by relativistic hydrodynamics [1], established [2,3,4,5] the formation of a collective medium in such collisions. The hydrodynamic EPOS3 event generator follows a similar particle production mechanism in pp, p-nucleus and nucleus-nucleus collisions, and has become a suitable testing ground for understanding the observed flow-like features in the high-multiplicity pp and pPb events at the LHC in comparison with the well-studied collective phenomena in relativistic nucleusnucleus collisions.

EVENT GENERATOR

Long-range ridge-like correlations

N trig d2Nassoc dΔηdΔφ

Blast-wave parametrization

Multiplicity-dependent inverse slope parameter of mT distributions

SUMMARY AND CONCLUSION