Abstract

We present the transverse momentum (PT) spectra for identified charged pions, protons and anti-protons from p + p and d + Au collisions at root sNN = 200 GeV. The spectra are measured around midrapidity (vertical bar y vertical bar 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 x(T)-scating for the momentum range where particle production is dominated by hard processes (p(T) greater than or similar to 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. (c) 2006 Elsevier B.V. All rights reserved.