Recent STAR Results from U+U and Au+Au Collisions

Abstract

Unlike Au or Pb nuclei which are more spherical, the uranium nuclei have a relatively large deformation on average. The prolate shape of uranium nuclei provides the feasibility to study how the initial geometry of the nuclei affects the azimuthal distributions of produced particles. It also provides a unique opportunity to understand the initial condition for particle production at mid-rapidity in heavy ion collisions as well as path length dependence of jet quenching and quarkonium in-medium effects.In this proceedings, the two- and four- particle cumulant, v2{2} and v2{4}, from U+U collisions at = 193 GeV and Au+Au collisions at = 200 GeV for inclusive charged hadrons at midrapidity will be presented. The STAR Zero Degree Calorimeter is used to subdivide the 0-1% centrality bin into even finer centralities. Differences were observed between the multiplicity dependence of v2{2} for most central Au+Au and U+U collisions. The observed v2{2} slope results were compared to Monte Carlo Glauber model predictions and it was seen that this model cannot explain the presented results on the multiplicity dependence of v2{2} in central collisions.