High pT physics at STAR

The STAR experiment at RHIC took data at √SNN = 130 and 200 GeV. Observation of a clear peak in two particle correlation at small relative pseudorapidity and azimuthal angle between the high pT charged particles show the presence of jets. The charged particle spectra at high transverse momenta shows suppression when compared with the nucleon-nucleon reference. A large elliptic flow is observed at high pT. New observation of two particle correlation at larger relative azimuthal angle between particles show the disappearance of back to back correlation for central collisions. All these observations taken together suggest that the core of the collision is opaque and that jets are observed, meaning large energy loss of partons or their fragments. (author)