Identified hadrons and jet chemistry for p+p and Au+Au collisions at RHIC

Abstract

The study of hadron spectra at high pT in p+p collisions provides a good test of perturbative quantum chromo-dynamic calculations (pQCD) and a baseline for measurements of nuclear modification factors in Au+Au collisions. Using events triggered with electro-magnetic calorimetery, identified charged hadron transverse momentum (pT) spectra are measured up to 15 GeV/c at mid-rapidity (|y| < 0.5) and neutral kaon pT spectra up to 12 GeV/c in p+p collisions at = 200 GeV in the STAR experiment (Ackermann K H et al 2003 Nucl. Instrum. Methods A 499 624. The particle ratios of p/π+, and K±, 0/π± in p+p collisions are shown and compared with next-to-leading-order pQCD calculations. In central Au+Au collisions, we report nuclear modification factors (RAA) for pion, kaon, proton and ρ, and discuss several model calculations: color-charge dependence of jet quenching and jet conversion. Finally, the centrality dependence of RAA at high pT (> 5.5 GeV/c) for kaons is compared with that of pions in Au+Au collisions at 200 GeV.