| The PHENIX experiment at RHIC has measured charged hadron yields at mid-rapidity over a wide range of transverse momentum (0.5 < pT < 10 GeV/c) in Au − Au collisions at = 200 GeV. The data are compared to π0 measurements from the same experiment. For both charged hadrons and neutral pions, the yields per nucleon-nucleon collision are significantly suppressed in central collisions compared to both peripheral and nucleon-nucleon collisions. The suppression sets in gradually and increases with increasing centrality of the collisions. Above 4–5 GeV/c in pT , a constant and almost identical suppression of charged hadrons and π0's, is observed. The ratio h/π 0 is ∼1.6 for all centralities. This value is consistent with the particle composition observed in p − p data at lower . The pT spectra are compared to published spectra from Au − Au at = 130 in terms of xT scaling. Central and peripheral π0 as well as peripheral charged spectra exhibit the same xT scaling as observed in p − p data. The charged hadron suppression is also compared with results from d − Au collisions. The yield per nucleon-nucleon collisions shows a small enhancement, strikingly different from the suppression seen in central Au − Au collisions, and indicates that the suppression in Au − Au collisions is not an initial state effect. The data presented in this work were published in [50, 52, 55, 153].; The measured centrality dependence of suppression of hadron yield, suppression of back-to-back correlation and azimuthal anisotropy all imply a strong dependence on the underlying collision geometry. We present a simple model of jet absorption in dense matter which incorporates a realistic nuclear geometry. This model describes quantitatively the observed suppression of the high p T hadron yield and of the back-to-back angular correlations. The azimuthal anisotropy of high pT particle production is described qualitatively. |
