# QM 2011 - XXII International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

May 22 – 28, 2011
Centre Bonlieu
Europe/Zurich timezone

## Interference effects in medium--induced gluon radiation

May 23, 2011, 3:40 PM
20m
Salon Ravel AB (Imperial Palace)

### Salon Ravel AB

#### Imperial Palace

Parallel New theoretical developments

### Speaker

Dr Jorge Casalderrey Solana (CERN)

### Description

The recent results at the LHC on jet quenching in heavy ion collisions call for a fundamental understanding of the evolution of a relatively hard jet propagating through a QCD medium like the quark--gluon plasma. As a first step in that sense, we consider the interference pattern for the medium--induced gluon radiation produced by a color singlet quark--antiquark antenna embedded in a QCD medium with size $L$. This setup is indeed well suited for studies of coherence phenomena like angular ordering. We focus on the most favorable kinematics for medium--induced gluon radiation in the BDMPS--Z regime, that is transverse momenta $k_\perp \sim \sqrt{\hat q L}$, short formation times $\tau_f \ll L$, and relatively large emission angles $\theta \gtrsim \theta_f\equiv(\hat q/\omega)^{1/3}$ ($\hat q$ is the medium `jet quenching' parameter and $\omega$ is the gluon energy). We demonstrate that, for a dipole opening angle $\theta_{q\bar q}$ larger than $\theta_f$, there is no interference between medium--induced gluon emissions by the quark and the antiquark. That is, the in--medium contribution to the antenna pattern is the incoherent superposition of two individual BDMPS--Z spectra. Physically, this is so since, unlike the direct emissions which can be delocalized anywhere throughout the medium, the interference terms are non--zero only for the very early emissions, such that the size of the $q\bar q$ dipole at the time of emission be smaller than the transverse wavelength of the emitted gluon.

 Slides