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.
Primary authors
Dr
Edmon Iancu
(CEA Saclay)
Dr
Jorge Casalderrey Solana
(CERN)
