Multiple jets and γ-jet correlation in high-energy heavy-ion collisions

Abstract

γ-jet production is considered one of the best probes of the hot quark-gluon plasma in high-energy heavy-ion collisions since the direct γ can be used to gauge the initial energy and momentum of the associated jet. This is investigated within the Linear Boltzmann Transport (LBT) model for jet propagation and jet-induced medium excitation. With both parton energy loss and medium response from jet-medium interaction included, LBT can describe experimental data well on γ-jet correlation in Pb+Pb collisions at the Large Hadron Collider. Multiple jets associated with direct γ production are found to contribute significantly to γ-jet correlation at small p jet T < p γ T and large azimuthal angle relative to the opposite direction of γ. Jet medium interaction not only suppresses the leading jet at large p jet T but also sub-leading jets at large azimuthal angle. This effectively leads to the narrowing of γ-jet correlation in azimuthal angle instead of broadening due to jet-medium interaction. The γ-jet profile on the other hand will be broadened due to jet-medium interaction and jet-induced medium response. Energy flow measurements relative to the direct photon is illustrated to reflect well the broadening and jet-induced medium response.

Interplaying mechanisms behind single inclusive jet suppression in heavy-ion collisions

“…Inelastic processes 2 → 2 + n with multiple gluon radiation and global energy-momentum conservation have also been implemented more consistently in the latest version [27,49,58]. It has been used to describe both single inclusive light and heavy flavor hadron suppression [50], γ-hadron [40], γ-jet [27,41,59] and Z 0 -jet correlations [60]. We will use it to study single inclusive jet suppression in high-energy heavy-ion collisions in this paper.…”

“…In heavy-ion collisions, however, the final jet production cross section is not only modified by parton energy loss of leading partons but also is influenced by how the lost energy is transported in the medium through radiated gluons and recoil medium partons. It is therefore imperative to include the effect of recoil partons and their further propagation in the form of jet-induced medium response as well as the propagation of radiated gluons in the study of jet suppression and medium modification [27,30,[35][36][37][38][39][40][41].…”

“…In this paper, we will use the Linear Boltzmann Transport (LBT) model [27,41,[47][48][49][50] for jet interaction and propagation in dense QGP medium to study the suppression of single inclusive jet spectra in high-energy heavyion collisions. We will pay particular attention to effects of recoil thermal partons and their further propagation in the dense medium whose evolution in high-energy heavyion collisions is described by a 3+1D viscous relativistic hydrodynamic model.…”

Molière scattering in quark-gluon plasma: finding point-like scatterers in a liquid

“…There are many extant measurements of the modification of jet shape observables in heavy ion collisions [18,19,21,23,25,[41][42][43][44][45], and many theorists have made efforts to turn these measurements into constraints on transverse momentum broadening, for example see Refs. [28,35,37,[46][47][48][49][50], but there are two significant confounding effects that obscure transverse momentum broadening [28]. The first effect is that the energy and momentum "lost" by the jet becomes a wake in the plasma which then in turn becomes soft particles spread over a large range of angles around the jet direction, carrying momentum in the jet direction.…”

Jet substructure and jet-induced medium response

“…The LBT model has been used to describe both single inclusive light and heavy flavor hadron suppression [5], γ-hadron [6], γ-jet [7] and Z 0 -jet correlations [8]. To study the medium modification of single inclusive and γ-jets, initial jet production in p+p collisions is simulated with PYTHIA.…”