Probing initial states at RHIC through particle production at forward and backward rapidities using PHENIX muon arms

Abstract

Particle multiplicities have yielded some of the most interesting insights at RHIC (Relativistic Heavy Ion Collider). To study the initial state effects at RHIC, we need to look at the small-x region in the gold nucleus, which can be achieved by going to forward rapidities (in the deuteron going direction) for d+Au collisions at √sNN = 200 GeV. We measure charged hadrons at forward and backward rapidities using the PHENIX north and south muon arms for d+Au collisions at √sNN = 200 GeV. We observe a Cronin-like enhancement on the gold going direction and a suppression on the deuteron going direction. This is qualitatively consistent with the expectation of shadowing/saturation type effects in the small-x region, which is probed at forward rapidities. However the enhancement at backward rapidities has not been explained.