Cherenkov gluons at RHIC and LHC

The coherent hadron production analogous to Cherenkov radiation of photons gives rise to the ring-like events. Being projected on the ring diameter they produce the two-bump structure recently observed for the away-side jets at RHIC. The position of the peaks and their height determine such properties of the hadronic medium as its nuclear index of refraction, the parton density, the free-path length and the energy loss of Cherenkov gluons. Beside comparatively low-energy gluons observed at RHIC, there could be high-energy gluons at LHC, related to the high-energy region of a positive real part of the forward scattering amplitude and possessing different characteristics