Vacuumlike Jet Fragmentation in a Dense QCD Medium.

P Caucal,E Iancu,G Soyez,A H Mueller

doi:10.1103/physrevlett.120.232001

Abstract

We study the fragmentation of a jet propagating in a dense quark-gluon plasma. Using a leading, double-logarithmic approximation in perturbative QCD, we compute for the first time the effects of the medium on multiple vacuumlike emissions. We show that, due to the scatterings off the plasma, the in-medium parton showers differ from the vacuum ones in two crucial aspects: their phase-space is reduced and the first emission outside the medium can violate angular ordering. We compute the jet fragmentation function and find results in qualitative agreement with LHC measurements.

Highlights

Introduction.—One of the main objectives of the experimental programs at the RHIC and at the LHC is the characterization of the quark-gluon plasma (QGP) produced in ultrarelativistic heavy ion collisions
An important class of observables used to study this dense form of QCD matter refers to the physics of “jet quenching,” i.e., the modifications of the properties of an energetic jet or a hadron due to its interactions with the surrounding medium
In this Letter, we study for the first time the effects of the medium on the vacuumlike parton cascades within controlled approximations in perturbative QCD

Summary

Vacuumlike Jet Fragmentation in a Dense QCD Medium

Doublelogarithmic approximation in perturbative QCD, we compute for the first time the effects of the medium on multiple vacuumlike emissions. In this Letter, we study for the first time the effects of the medium on the vacuumlike parton cascades within controlled approximations in perturbative QCD. Conclusion is that the jet fragmentation can be computed in a leading, double-logarithmic approximation in which such cascades can be factorized from medium-induced emissions. In this approximation, which is common in perturbative QCD [15], jet branching is governed by the usual, DokshitzerGribov-Lipatov-Altarelli-Parisi (DGLAP), splitting functions in the vacuum. The emissions in the third stage follow the same pattern as the genuine parton showers

Published by the American Physical Society

Findings

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