Identified hadron spectra at large transverse momentum in p + p and d + Au collisions at sqrt(sNN) = 200  GeV

Abstract

We present the transverse momentum ( pT) spectra for identified charged pions, protons and anti-protons from p + p and d + Au collisions at sqrt(sNN) = 200   GeV. The spectra are measured around midrapidity ( | y | < 0.5) over the range of 0.3 < pT < 10   GeV / c with particle identification from the ionization energy loss and its relativistic rise in the time projection chamber and time-of-flight in STAR. The charged pion and proton + anti-proton spectra at high pT in p + p and d + Au collisions are in good agreement with a phenomenological model (EPOS) and with next-to-leading order perturbative quantum chromodynamic (NLO pQCD) calculations with a specific fragmentation scheme and factorization scale. We found that all proton, anti-proton and charged pion spectra in p + p collisions follow xT-scaling for the momentum range where particle production is dominated by hard processes ( pT ≳ 2   GeV / c). The nuclear modification factor around midrapidity is found to be greater than unity for charged pions and to be even larger for protons at 2 < pT < 5   GeV / c. © 2006 Elsevier B.V. All rights reserved.