Multi-particle correlations and KNO scaling in the medium-induced jet evolution

Abstract

We study the gluon distribution produced via successive medium-induced branchings by an energetic jet propagating through a weakly-coupled quark-gluon plasma. We show that under suitable approximations the evolution of the jet can be described as a classical stochastic process, which is exactly solvable. For this process, we construct exact analytic solutions for all the n-point correlation functions (the n-body densities in the space of energy). The corresponding results for the one-point and the two-point functions were already known, but those for the higher-point functions are new. These results demonstrate strong correlations associated with the existence of common ancestors in the branching process. By integrating these n-point functions over the gluon energies, we deduce the mean gluon multiplicity $⟨N⟩$ as well as the higher moments $⟨N^p⟩$ with $p\ge 2$. We find that the multiplicities of the soft gluons are parametrically large and show a remarkable regularity, known as Koba-Nielsen-Olesen (KNO) scaling: the reduced moments $⟨N^p⟩/⟨N{⟩}^p$ are pure numbers, independent of any of the physical parameters of the problem. We recognize a special negative binomial distribution which is characterized by large statistical fluctuations. These predictions can be tested in Pb+Pb collisions at the LHC, via event-by-event measurements of the di-jet asymmetry.

31 pages, 7 figures

References in corpus (9)

• Measurement of jet fragmentation in PbPb and pp collisions at sqrt(s[NN]) = 2.76 TeV
• Antiangular Ordering of Gluon Radiation in QCD Media
• Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV with the ATLAS detector
• Picturing perturbative parton cascades in QCD matter
• Angular structure of the in-medium QCD cascade
• Medium-induced gluon radiation and colour decoherence beyond the soft approximation
• The non-linear evolution of jet quenching
• Angular distribution of medium-induced QCD cascades
• Radiative energy loss and radiative p_T-broadening of high-energy partons in QCD matter