Nuclear Effects on Hadron Production in d+Au and p+p Collisions at sqrt(s_NN)=200 GeV

Abstract

PHENIX has measured the centrality dependence of mid-rapidity pion, kaon andproton transverse momentum distributions in d+Au and p+p collisions atsqrt(s_NN) = 200 GeV. The p+p data provide a reference for nuclear effects ind+Au and previously measured Au+Au collisions. Hadron production is enhanced ind+Au, relative to independent nucleon-nucleon scattering, as was observed inlower energy collisions. The nuclear modification factor for (anti) protons islarger than that for pions. The difference increases with centrality, but isnot sufficient to account for the abundance of baryon production observed incentral Au+Au collisions at RHIC. The centrality dependence in d+Au shows thatthe nuclear modification factor increases gradually with the number ofcollisions suffered by each participant nucleon. We also present comparisonswith lower energy data as well as with parton recombination and othertheoretical models of nuclear effects on particle production.