Radiative energy loss in an absorptive QED/QCD-plasma

Marcus Bluhm, U. of Torino and INFN
March 21, 2013, 3:30 pm

A firm knowledge of medium-induced energy loss mechanisms in the Quark-Gluon Plasma is essential for our understanding of phenomena like the suppression of hadrons at large transverse momenta as is being observed in high-energy nuclear collisions at RHIC and LHC. It is commonly accepted that the radiative energy loss dominates over the collisional energy loss contribution for large parton energies. In the underlying theoretical studies, however, the possible influence of a damping of the bremsstrahlung gluons in an absorptive plasma has so far been neglected.

In this talk, it is argued that in an infinite, absorptive and polarizable plasma the radiative energy loss can become significantly affected for charges with high initial energy. This is because damping mechanisms in a dissipative medium may influence the formation of the radiation quanta, in particular, when their formation times are large. These findings are based on explicit calculations for an absorptive QED-plasma. Nevertheless, formation time arguments allow for a semi-quantitative extension of the considerations to the case of an absorptive QCD-plasma. Phenomenological consequences for the quenching of heavy-quarks are presented. Finite medium-size effects can nullify these results only if the length-scales associated with the damping mechanisms are large compared to the size of the medium.