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Jet Quenching

R. Baier

TL;DR

Jet quenching addresses how energetic partons lose energy in a quark-gluon plasma and how this manifests as suppressed high-$p_T$ hadron production. The paper advocates a pQCD-based approach (BDMPS) where medium-induced gluon radiation, governed by the transport coefficient $\hat{q}$ and a finite-size energy scale $\omega_c$, dominates energy loss, with the spectrum $dI/d\omega$ exhibiting coherence effects. It connects the microscopic dynamics to observables via the energy-loss distribution $D(\epsilon)$ and the quenching factor $Q(p_T)$, and it also translates energy loss into medium-modified fragmentation functions, highlighting heavy-quark dead-cone suppression. The results indicate significant quenching at RHIC energies for accessible $p_T$, demonstrate how quenching scales with medium density and expansion, and outline a program to extract medium properties from jet observables, including predictions for LHC jet physics. Overall, the framework provides a quantitative bridge between QGP properties and jet observables, while identifying open questions about the medium's non-equilibrium stages and collision geometry.

Abstract

A short summary of the physics underlying jet quenching is given

Jet Quenching

TL;DR

Jet quenching addresses how energetic partons lose energy in a quark-gluon plasma and how this manifests as suppressed high- hadron production. The paper advocates a pQCD-based approach (BDMPS) where medium-induced gluon radiation, governed by the transport coefficient and a finite-size energy scale , dominates energy loss, with the spectrum exhibiting coherence effects. It connects the microscopic dynamics to observables via the energy-loss distribution and the quenching factor , and it also translates energy loss into medium-modified fragmentation functions, highlighting heavy-quark dead-cone suppression. The results indicate significant quenching at RHIC energies for accessible , demonstrate how quenching scales with medium density and expansion, and outline a program to extract medium properties from jet observables, including predictions for LHC jet physics. Overall, the framework provides a quantitative bridge between QGP properties and jet observables, while identifying open questions about the medium's non-equilibrium stages and collision geometry.

Abstract

A short summary of the physics underlying jet quenching is given

Paper Structure

This paper contains 8 sections, 20 equations, 11 figures.

Table of Contents

  1. Introduction
  2. pQCD medium-induced radiative energy loss
  3. Transport coefficient $\hat{q}$
  4. How to "measure" $\Delta E(L)$ ?
  5. Quenching of leading hadron spectra in media baier
  6. Medium-modified fragmentation functions
  7. Heavy quark radiative energy loss and quenching dima
  8. Summary and conclusions

Figures (11)

  • Figure 1: Typical gluon radiation diagram
  • Figure 2: Medium-induced soft gluon spectrum
  • Figure 3: Transport coefficient as a function of energy density for different media: cold, massless hot pion gas (dotted) and (ideal) QGP (solid curve)
  • Figure 4: Gluon radiation probability arleo
  • Figure 5: The quenching factor $Q (p_{\perp})$baier
  • ...and 6 more figures