A perturbative framework for jet quenching

Abstract

We present a conceptually new framework for describing jet evolution in the dense medium produced in ultra-relativistic nucleus-nucleus collisions using perturbative QCD and its implementation into the Monte Carlo event generator Jewel. The rescattering of hard partons in the medium is modelled by infrared continued pQCD matrix elements supplemented with parton showers. The latter approximate higher order realemission matrix elements and thus generate medium-induced gluon emissions. The interplay between different emissions is governed by their formation times. The destructive interference between subsequent scattering processes, the non-Abelian version of the Landau-Pomeranchuk-Migdal effect, is also taken into account. In this way the complete radiation pattern is consistently treated in a uniform way. Results obtained within this minimal and theoretically well constrained framework are compared with a variety of experimental data susceptible to jet-quenching effects at both RHIC and the LHC. Overall, a good agreement between data and simulation is found. This new framework also allows to identify and quantify the dominant uncertainties in the simulation, and we show some relevant examples for this.

Angular structure of jet quenching within a hybrid strong/weak coupling model

“…(See ref. [105] for a similar effect in a perturbative-based jet quenching Monte Carlo [76,77,81,82].) The small-z region of the fragmentation function is sensitive to backreaction effects.…”

“…[70][71][72][73][74][75] for reviews.) Based on these approaches, Monte Carlo tools for analyzing jet observables are being developed [76][77][78][79][80][81][82][83] and many phenomenological studies of jets in medium have been confronted with LHC measurements of a variety of jet observables , including intrajet observables like those that we shall focus on [85,89,99,101,104,[106][107][108][109].…”

Theory of jet quenching in ultra-relativistic nuclear collisions

“…These results indicate that the away-side subleading jets experience significant amount of energy loss when propagating through the produced QGP. Various model calculations based on jet energy loss have been performed to explain the observed dijet and γ-jet momentum imbalance [22,52,53,54,55,56,57,58,59,60,61].…”

Interplay between hydrodynamics and jets

“…The QCD evolution of jets in the presence of re-scattering in a dense background is simulated with Jewel [4]. The jet production points are distributed according to the density of binary nucleon-nucleon collisions extracted from 1 a Glauber model [5].…”

“…So far, Jewel was used mainly with a simple toy model as background, which assumes Bjorken expansion and an energy density that is proportional to the density of participants calculated in a Glauber model [4]. The initialisation time and initial temperature are the same in the toy model and the full fluid dynamical evolution, but the temperature profile in the transverse plane is different (it falls off faster in the hydro initial conditions).…”