A local Monte Carlo framework for coherent QCD parton energy loss

140

226

We study the evolution of an energetic jet which radiates gluons while propagating through a dense QCD medium modeled as a random distribution of color sources. Motivated by the heavy ion experimental program at the LHC, we focus on the mediuminduced radiation of (relatively) soft gluons, which are abundantly emitted at large angles and thus can transport a small fraction of the jet energy far away from the jet axis. We perform a complete calculation of the medium-induced gluon branching in the regime where the gluons that take part in the branching undergo multiple soft scattering with the medium. We extend the BDMPSZ theory of radiative energy loss by including the transverse momentum dependence in the kernel that describes the branching and by analyzing the correlations between the two offspring gluons. We demonstrate that these gluons lose color coherence with respect to each other over a time scale that is comparable to the duration of the branching. It follows that interference effects between successive emissions are suppressed, a necessary ingredient for a description of multiple emission of soft gluons by a probabilistic, branching process.

“…[33][34][35]. Our conclusion shows how this approach is justified theoretically in the desired kinematical regime where multiple emissions are indeed important.…”

Section: Jhep01(2013)143mentioning

confidence: 55%

Medium-induced gluon branching

Blaizot

Domínguez

Iancu

et al. 2013

140

226

“…Partons belonging to a jet may interact with these background partons through 2 → 2 scattering processes described by perturbative matrix elements, with associated gluon emission generated by the parton shower. Further details of the inner workings and Monte Carlo implementation of Jewel are available in [32,34].…”

Section: Treatment Of Medium Response In Jewelmentioning

confidence: 99%

Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions

Elayavalli

Zapp

2017

Self Cite

119

Realistic modeling of medium-jet interactions in heavy ion collisions is becoming increasingly important to successfully predict jet structure and shape observables. In Jewel, all partons belonging to the parton showers initiated by hard scattered partons undergo collisions with thermal partons from the medium, leading to both elastic and radiative energy loss. The recoiling medium partons carry away energy and momentum from the jet. Since the thermal component of these recoils' momenta is part of the soft background activity, comparison with data requires the implementation of a subtraction procedure. We present two independent procedures through which background subtraction can be performed and discuss the impact of the medium recoil on jet shape observables. Keeping track of the medium response significantly improves the Jewel description of jet shape measurements.

“…The medium-induced single-inclusive spectrum off a single charge, known henceforth as the BDMPS-Z spectrum, serves also as a building block for treating multigluon emissions, see, e.g., [31,32]. These ad hoc extensions can therefore only account for uncorrelated emissions (except for trivial correlations such as energy-momentum conservation) and serve as working models for phenomenological applications and Monte-Carlo implementations, e.g., [33][34][35][36].…”

Section: Jhep10(2012)197 1 Introductionmentioning

confidence: 99%

The radiation pattern of a QCD antenna in a dense medium

Mehtar-Tani

Salgado

Tywoniuk

2012

Abstract:We calculate the radiation spectrum off a qq pair of a fixed opening angle θ qq traversing a medium of length L. Multiple interactions with the medium are handled in the harmonic oscillator approximation, valid for soft gluon emissions. We discuss the time-scales relevant to the decoherence of correlated partons traversing the medium and demonstrate how this relates to the hard scale that govern medium-induced radiation. For large angle radiation, the hard scale is given by Q hard = max r −1 ⊥ , Q s , where r ⊥ = θ qq L is the probed transverse size and Q s is the maximal transverse momentum accumulated by the emitted gluon in the medium. These situations define in turn two distinct regimes, which we call "dipole" and "decoherence" regimes, respectively, which are discussed in detail. A feature common to both cases is that coherence of the radiation is restored at large transverse momenta, k ⊥ > Q hard .