d+Au at PHENIX: Insights on the Cronin effect, shadowing and saturation

Abstract

Wit Busza pioneered the study of proton-nucleus collisions in order to understand how nucleons lose energy to the nuclear medium and how multiple interactions can affect particle production. These are questions of paramount importance for formation of quark gluon plasma in ion-ion collisions. In this proceedings I report insights on nuclear shadowing, saturation, and the Cronin effect drawn from d+Au collisions at RHIC. The study of proton-nucleus collisions has been of great interest for many years. Much of the experimental and phenomenological work has been done thanks to the inspiration and leadership of Wit Busza. This remains true at RHIC, where collisions of deuterons on gold nuclei have been used in lieu of p+Au. Beginning in 2015, RHIC will provide proton-nucleus collisions, as well. In the pre-RHIC era, the big question driving p+A collisions was "What do subsequent p-nucleon collisions in p+A have to do with one another?" Wit Busza was our intellectual leader in addressing this question, and in finding the answer, which was "quite a bit". Now, the focus has shifted as colliders allow one to probe much smaller values of momentum fraction, x, than was accessible in fixed target experiments. Now, the question is "What do gluons at small x inside a nucleus have to do with one another?" Again, the answer seems to be "quite a bit", but the range of theoretical predictions, and physics processes which may contribute, is enormous.

Proceedings of 2016 International Conference on Ultra-High Energy Cosmic Rays (UHECR2016)

“…Recent summaries from experiments and their interpretation at RHIC and LHC can be found e.g. in [10,11].…”