Evidence of finite sQGP formation time at RHIC

We demonstrate that the existence of a finite formation time of strongly interacting plasma in nuclear collisions at RHIC is an inavitable conclusion from recent experimental data. The most striking feature of the experimental data an absense of absorption of high transverse momentum pions in the rection plane direction for mid-peripheral collisions points to the presence of a surface zone with no absorption and strong suppression in the inner core. A natural interpretation of such a zone should be the plasma formation time T≃ 2-3 fm/c. We discuss constraints induced by finite formation time on some physical observables at RHIC. Nuclear modification factor, azimuthal assymetry, di-jet correlations can quantitatively be described by particle production in the early stage of the nuclear collision. A possible impact on azimuthal anisotropy at lower hardon momenta, on interpretation of the non-photonic electrons and J/ψ data is also considered.