Abstract

A parton produced with a high transverse momentum in a hard collision is regenerating its color field, intensively radiating gluons and losing energy. This process cannot last long, if it ends up with production of a leading hadron carrying the main fraction zh of the initial parton momentum. So energy conservation imposes severe constraints on the length scale of production of a single hadron with high p(T). As a result, the main reason for hadron quenching observed in heavy ion collision is not energy loss, but attenuation of the produced colorless dipole in the created dense medium. The latter mechanism, calculated with the path-integral methods, explains well the observed suppression of light hadrons and elliptic flow in a wide range of energies, from the lowest energy of RHIC up to LHC, and in a wide range of transverse momenta. The values of the transport coefficient extracted from data range within 1-2 GeV2/fm, dependent on energy, so agree well with the theoretical expectations.