Hadronization in Nuclear Matter

Nuclei are unique analyzers of the space-time development of jets at early stage. We argue that the gluon bremsstrahlung, rather than the color string, is the main mechanism of hadronization of highly virtual quarks produced in a hard interaction. It results in an energy- and time-independent density of energy loss, like a color string, but steeply dependent on the quark virtuality. Effects of formation zone (FZ) and color transparency (CT) substantially affect the jet quenching in a nuclear matter. The latter also plays an important role in the broadening of transverse momentum distribution of a quark passing a nucleus. Parameter-free calculations provide a good description of available data on nuclear effects in the leading hadron production in deep-inelastic lepton scattering, back-to-back high-$p_T$ hadron pair production, broadening of the transverse momentum distribution in the Drell-Yan process of lepton pair production on nuclei.