Event-by-event fluctuations in the medium-induced jet evolution

Miguel A. Escobedo (1) , Edmond Iancu (1)

1 IPHT - Institut de Physique Théorique - UMR CNRS 3681

We develop the event-by-event picture of the gluon distribution produced via medium-induced gluon branching by an energetic jet which propagates through a dense QCD medium. A typical event is characterized by the production of a large number of soft gluons which propagate at large angles with respect to the jet axis and which collectively carry a substantial amount of energy. By explicitly computing 2-gluon correlations, we demonstrate the existence of large event-by-event fluctuations, which reflect the stochastic nature of the branching process. For the two quantities that we have investigated -- the energy loss at large angles and the soft gluon multiplicity --, the dispersion is parametrically as large as the respective expectation value. We identify interesting scaling laws, which suggest that the multiplicity distribution should exhibit KNO (Koba-Nielsen-Olesen) scaling. A similar scaling is known to hold for a jet branching in the vacuum, but the medium-induced distribution is found to be considerably broader. We predict that event-by-event measurements of the di-jet asymmetry in Pb+Pb collisions at the LHC should observe large fluctuations in the number of soft hadrons propagating at large angles and also in the total energy carried by these hadrons.

Domaines: Physique des Hautes Energies - Phénoménologie [hep-ph]; Physique des Hautes Energies - Expérience [hep-ex]; Physique Nucléaire Théorique [nucl-th]

Miguel A. Escobedo, Edmond Iancu. Event-by-event fluctuations in the medium-induced jet evolution. 2016. ⟨cea-01296822⟩