Jets in heavy ion collisions

High energetic particles traversing a dense medium lose a sizable part of their energy in form of gluon radiation. As a result, the rate of high-$p_t$ particles is expected to be suppressed in heavy ion collisions with respect to the proton case. Recent experimental data from RHIC strongly support this scenario. This allows to study the properties of the medium by the amount of jet quenching it produces. The angular dependence of the radiation is modified in the medium in a characteristic way. This provides another tool to study the medium properties in a more differential measurement.