Hard dihadron correlations in heavy-ion collisions at energies available at the BNL Relativistic Heavy Ion Collider and CERN Large Hadron Collider

Abstract

High transverse momentum (${P}_{T}$) processes are considered to be an important tool to probe and understand the medium produced in ultrarelativistic heavy-ion collisions via the interaction of hard, perturbatively produced partons with the medium. In this context, triggered hard dihadron correlations constitute a class of observables set between hard single inclusive hadrons (dominated by the leading jet fragments) and fully reconstructed jets; while they probe some features of the perturbative QCD evolution of a parton shower in the medium, they do not suffer from the problem of finding a suitable separation between soft hadrons coming from perturbative jets and soft hadrons coming from the nonperturbative medium as the identification of full jets does. On the other hand, the trigger requirement introduces nontrivial complications to the process, which makes the medium modification of the correlation pattern difficult and nonintuitive to understand. In this work, we review the basic physics underlying triggered dihadron correlations and make a systematic comparison of several combinations of medium evolution and parton-medium interaction models with the available data from 200-AGeV Au-Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC). We also discuss the expected results for 2.76-ATeV Pb-Pb collisions at the CERN Large Hadron Collider (LHC).