Cold Nuclear Matter Effects at PHENIX

Abstract

Abstract While the study of the quark-gluon plasma has been the primary focus of the RHIC experiments, much work has also been done to understand so-called cold nuclear matter (CNM) effects through d + Au collisions where no hot plasma is produced. Effects such as nuclear shadowing, Cronin enhancement, and initial-state parton energy loss, among others, are not only interesting in their own right, but have direct implications on QGP-related measurements in A + A collisions. Recently PHENIX has measured CNM effects at midrapidity in s NN = 200 GeV d + Au collisions. Measurements of reconstructed jets reveal the centrality dependence of both jet suppression and broadening of the away-side jet. Meanwhile, single electrons from heavy flavor decays exhibit enhancement, increasing with centrality, over a broad p T range. J / ψ and ψ ′ modification have also been measured and are quite different in magnitude, in contrast with our expectations. The above results are presented here and compared to our present understanding of CNM effects.