Jet Quenching and Radiative Energy Loss in Dense Nuclear Matter

TL;DR

The paper assesses finite-opacity, non-Abelian radiative energy-loss formalisms (GLV and WW) and the twist-expansion WOGZ approach to parton energy loss in dense QCD matter. It develops a reaction-operator formalism for GLV, includes detailed balance via WW, and extends to generalized factorization with twist-4 corrections in WOGZ, enabling predictions for both hot and cold nuclear media. The frameworks are applied to jet quenching observables, Cronin effects, baryon/meson ratios, and high-$p_T$ azimuthal anisotropy, yielding tomographic inferences of initial gluon densities and transport coefficients at SPS, RHIC, and LHC. The work highlights the potential of jet tomography to reveal the evolution of quark-gluon plasma while noting uncertainties such as gluon shadowing and finite-kinematic effects.

Abstract

We review recent finite opacity approaches (GLV, WW, WOGZ) to the computation of the induced gluon radiative energy loss and their application to the tomographic studies of the density evolution in ultra-relativistic nuclear collisions.

Figures (28)

• Figure 1: HIJING predictionsWang:1992xy of the inclusive charged hadron spectra in central $Au+Au$ and $p+Au$ collisions at $\sqrt{s}=200$ AGeV. The competing effects of minijet production (dash-dotted), gluon shadowing (dashed) (assuming that gluon shadowing is identical to that of quarks), and jet quenching (solid) with $dE/dx=$ 2 GeV/fm are shown. $R^{AB}(p_T)$ is the ratio of the inclusive $p_T$ spectrum of charged hadrons in $A+B$ collisions to that of $p+p$. In contrast to $Au+Au$, no significant quenching is expected in $p+Au$ (or $d+Au$) since only $\sim 20\%$ initial state shadowing and Cronin effects modify the pQCD spectrum at high $p_T$.
• Figure 2: Preliminary STARKunde:2002pb data on charged hadron quenching between central and peripheral $Au+Au$ collisions at $\sqrt{s}=200$ AGeV is shown for peripheral event classes. The data are scaled by the Glauber binary collision scaling factor for each centrality class. Upper gray band is the expected result from pQCD scaling from $p+p$. Lower gray bands correspond to scaling with the nucleon participant number instead. Beyond 4 GeV, charged hadrons are suppressed by 0.2-0.4 (factor 2.5 to 5) relative to naive binary scaling.
• Figure 3: Preliminary PHENIXMioduszewski:2002wt data on charged and $\pi^0$ hadron quenching between central and peripheral $Au+Au$ collisions at $\sqrt{s}=200$ AGeV is shown. The pions are generally more quenched than the summed charged hadrons ($\pi +K+p$).
• Figure 4: The striking contrast between PHENIXAdcox:2002pe data on $\pi^0$ quenching in central $Au+Au$ collisions at $\sqrt{s}=130$ AGeV compared to the (Cronin) enhancement found in $Pb+Pb$ at 17 AGeV fromAggarwal:1998vh demonstrates that jet quenching is a new nuclear phenomenon first seen at RHIC.
• Figure 5: Preliminary $\sqrt{s}=200$ AGeV PHENIXMioduszewski:2002wt data on $\pi^0$ quenching on central and peripheral $Au+Au$ collisions is compared relative to preliminary PHENIX data on $p+p$. Peripheral reactions are consistent with simple binary ($\sim A^{4/3}$) scaling from $p+p$ while in central collisions substantial quenching is observed.