Hard dihadron correlations in heavy-ion collisions at RHIC and LHC

TL;DR

This paper reviews the physics of triggered dihadron correlations in heavy-ion collisions, comparing models with RHIC data and discussing expectations for LHC, to better understand medium effects on parton showers.

Contribution

It systematically compares different medium evolution and parton-medium interaction models with experimental data, providing insights into the medium's impact on dihadron correlations.

Findings

Model comparisons with RHIC data elucidate medium effects.

Predictions for LHC collisions are discussed.

Understanding of medium-modified parton showers is advanced.

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 perturbative (jet-like) and soft non-perturbative (medium-like) physics as the identification of full jets does. On the other hand, the trigger requirement introduces non-trivial complications to the process, which makes the medium-modification of the correlation pattern difficult and non-intuitive 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 RHIC. We also discuss the expected results for 2.76 ATeV Pb-Pb collisions at the LHC.