Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at s=200 GeV
Identified mid-rapidity particle spectra of π, K, and p(p̄) from 200 GeV p+p and d+Au collisions are reported. A time-of-flight detector based on multi-gap resistive plate chamber technology is used for particle identification. The particle-species dependence of the Cronin effect is observed to be significantly smaller than that at lower energies. The ratio of the nuclear modification factor (R) between protons (p+p̄) and charged hadrons (h) in the transverse momentum range 1.2<p<3.0 GeV/c is measured to be 1.19±0.05(stat)±0.03(syst) in minimum-bias collisions and shows little centrality dependence. The yield ratio of (p+p̄)/h in minimum-bias d+Au collisions is found to be a factor of 2 lower than that in Au+Au collisions, indicating that the Cronin effect alone is not enough to account for the relative baryon enhancement observed in heavy ion collisions at RHIC.