Jet quenching

TL;DR

This review discusses jet quenching as a powerful probe of hot, dense QCD matter created in high-energy nucleus-nucleus collisions. It surveys perturbative and nonperturbative approaches to parton energy loss (BDMPS-ASW, DGLV, HT, AMY, and AdS/CFT), and confronts them with experimental data from RHIC and expectations for the LHC, highlighting the extraction of transport coefficients such as $\hat{q}$ and the initial gluon density $dN^g/dy$. The article details how high-$p_T$ hadron suppression, di-hadron correlations, and full jet observables constrain the medium’s temperature, density, and dynamical evolution, including the path-length and color-factor dependences, and heavy-quark dynamics. It also emphasizes the role of jet reconstruction and photon-jet correlations in providing a more differential view of in-medium parton showers and fragmentation, thereby offering a pathway to quantitatively map the QGP properties and its response to energetic probes.

Abstract

We present a comprehensive review of the physics of hadron and jet production at large transverse momentum in high-energy nucleus-nucleus collisions. Emphasis is put on experimental and theoretical "jet quenching" observables that provide direct information on the (thermo)dynamical properties of hot and dense QCD matter.

Figures (36)

• Figure 1: Examples of hard probes whose modifications in high-energy $AA$ collisions provide direct information on properties of QCD matter such as the transport coefficient ${\hat{q}}$, the initial gluon rapidity density $dN^g/dy$, and the critical temperature $T_{\hbox{\tiny{\it crit}}}$ and energy density $\varepsilon_{\hbox{\tiny{\it crit}}}$d'Enterria:2006su.
• Figure 2: "Jet quenching" in a head-on nucleus-nucleus collision. Two quarks suffer a hard scattering: one goes out directly to the vacuum, radiates a few gluons and hadronises, the other goes through the dense plasma created (characterised by transport coefficient ${\hat{q}}$, gluon density $dN^g/dy$ and temperature $T$), suffers energy loss due to medium-induced gluonstrahlung and finally fragments outside into a (quenched) jet.
• Figure 3: Diagrams for collisional (left) and radiative (right) energy losses of a quark of energy $E$ traversing a quark-gluon medium.
• Figure 4: Stopping power, $-dE/dl$, for positive muons in copper as a function of $\beta\gamma = p/Mc$ (or momentum $p$). The solid curve indicates the total stopping power Yao:2006px.
• Figure 5: Comparison of the average radiative and elastic energy losses of light-quarks (left) and light- and heavy-quarks (right) passing through the medium produced in central $AuAu$ collisions at RHIC energies as obtained by the AMY Qin:2007rn and DGLV Wicks:2005gt models (see later).