Photon production is used as a baseline for the hadron quenching phenomenon in heavy ion collisions because it interacts with the particles in the collision region through electromagnetic interaction. Following the BDMPS-Z/ASW approach, we calculated the medium-induced two-photon radiation spectrum [1] and found that, in the Moliere limit, the Landau-Pomeranchuk-Migdal effect still holds. Due to the non-Abelian nature, the gluon radiation "enjoys" the strong interaction with the medium. The medium-induced one-gluon radiation spectrum off a massive quark-antiquark antenna traversing a colored QCD medium was calculated in [2]. The interference between the two emitters dominates the soft gluon radiation when the antenna opening angle is small and the emitted gluon is soft, whereas the antenna behaves like a superposition of two independent emitters when the opening angle is large and the radiated gluon is hard. We investigated the average radiative energy loss by the antenna. In general, more collimated jets lose less energy. The broadening of the emitted gluon was also studied. In the soft gluon emission limit, the broadening of the emitted gluon is not due to the transverse kicks from the medium as in the independent emitter case, but due to the interference between different emitters. The antenna radiation in t-channel is being studied and some new interesting phenomena could lead to a better understanding of the partonic structure of protons and nuclei at small-x.

References:

[1] H. Ma, C. A. Salgado and K. Tywoniuk, J. Phys. Conf. Ser. 270 (2011) 012034 [arXiv:1105.5801 [hep-ph]].

[2] N. Armesto, H. Ma, Y. Mehtar-Tani, C. A. Salgado and K. Tywoniuk, JHEP 1201 (2012) 109 [arXiv:1110.4343 [hep-ph]].