The theory and phenomenology of perturbative QCD based jet quenching

Abstract

The study of the structure of strongly interacting dense matter via hard jets is reviewed. High momentum partons produced in hard collisions produce a shower of gluons prior to undergoing the non-perturbative process of hadronization. In the presence of a dense medium this shower is modified due to scattering of the various partons off the constituents in the medium. The modified pattern of the final detected hadrons is then a probe of the structure of the medium as perceived by the jet. Starting from the factorization paradigm developed for the case of particle collisions, we review the basic underlying theory of medium induced gluon radiation based on perturbative Quantum Chromo Dynamics (pQCD) and current experimental results from Deep Inelastic Scattering on large nuclei and high energy heavy-ion collisions, emphasizing how these results constrain our understanding of energy loss. This review contains introductions to the theory of radiative energy loss, elastic energy loss, and the corresponding experimental observables and issues. We close with a discussion of important calculations and measurements that need to be carried out to complete the description of jet modification at high energies at future high energy colliders.Comment: 78 pages, 24 figures, submitted to prog. part. nucl. phy

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

“…(See refs. [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].…”

Melting hadrons, boiling quarks

“…With increasing energy, like in pp, also in AA collisions hard parton back-scattering must occur, with a rate described by the perturbative QCD [165,166]. Such hard partons are observed in back-to-back jets, that is two jetlike assembly of particles into which the hard parton hadronizes.…”

Interference effects in medium-induced gluon radiation

“…While this mechanism for jet quenching has been quite successful in describing the suppression of single particle spectra observed at RHIC (see, for example [20,21]), it has been realized for long that the respective data refer to inclusive measurements which are quite limited in constraining the underlaying dynamics. By contrast, the differential jet measurements that are performed at the LHC provide more detailed informations, in particular, on the spectrum of the medium-induced radiation which could help us to better pinpoint the physical mechanisms at work.…”