Speaker
Description
A better understanding of parton dynamics in the nucleus, in particular in the small-x region, is extremely important as it is needed to understand the nature of recently observed and unexpected phenomena like particle anisotropies in small collision systems. PHENIX can explore the small and large-x regions in the nucleus through measurements in the muon arms and forward vertex trackers. These detectors cover the forward ($1.2<\eta<2.2$) and backward ($-2.2<\eta<-1.2$) rapidity range, which in p+Au collisions at 200 GeV gives access to an average x$\sim$0.005 and x$\sim$0.1, respectively. In this talk PHENIX present new results, including on charged hadrons, muon pairs from bottom decays, and Drell-Yan muon pairs. The ratio of p+Au to p+p data reveals interesting patterns of suppression and enhancement in the p+Au data. When comparing the results to pQCD calculations using nuclear parton distribution functions, reasonable agreement is found only over part of the accessible kinematic range, indicating the possible presence of other nuclear effects.
