Relativistic heavy ion collisions produce nuclei-sized droplets of quark-gluon plasma whose expansion is well described by viscous hydrodynamic calculations. Over the past half decade, this formalism ...was also found to apply to smaller droplets closer to the size of individual nucleons, as produced in p+p and p+A collisions. The hydrodynamic paradigm was further tested with a variety of collision species, including p+Au,d+Au , and He 3+Au producing droplets with different geometries. Nevertheless, questions remain regarding the importance of pre-hydrodynamic evolution and the exact medium properties during the hydrodynamic evolution phase, as well as the applicability of alternative theories that argue the agreement with hydrodynamics is accidental. In this work we explore options for new collision geometries including p+ O and O + O proposed for running at the Large Hadron Collider, as well as He 4+Au, C +Au, O +Au , and Be 7,9+Au at the Relativistic Heavy Ion Collider.
The study of numerous physics effects in small collision systems requires a careful characterization of the event geometry. In particular, many such phenomena have a strong dependence on the impact ...parameter of the collision. We describe the methodology utilized by PHENIX to select centrality classes in d+Au collisions via cuts on charge deposited at backward (Au-going) rapidity. The measured charge can be mapped to other geometric quantites using a Monte Carlo Glauber model. We also describe how autocorrelations between the process of interest and the backward rapidity charge introduce bias effects that alter the measurement of centrality-dependent invariant yields. Our framework provides a method to compute correction factors to account for such effects. We discuss their calculation and validation using the HIJING Monte Carlo Generator. It is found that centrality bias correction factors are small and slightly pT dependent for d+Au collisions at 200 GeV, yet an order of magnitude larger and strongly pT dependent for p+Pb collisions at 5.02 TeV. The implications of such corrections are discussed for selected physics observables and effects.
Relativistic heavy ion collisions produce nuclei-sized droplets of quark-gluon plasma whose expansion is well described by viscous hydrodynamic calculations. Over the past half decade, this formalism ...was also found to apply to smaller droplets closer to the size of individual nucleons, as produced in p+p and p+A collisions. The hydrodynamic paradigm was further tested with a variety of collision species, including p+Au,d+Au , and He 3+Au producing droplets with different geometries. Nevertheless, questions remain regarding the importance of pre-hydrodynamic evolution and the exact medium properties during the hydrodynamic evolution phase, as well as the applicability of alternative theories that argue the agreement with hydrodynamics is accidental. In this work we explore options for new collision geometries including p+ O and O + O proposed for running at the Large Hadron Collider, as well as He 4+Au, C +Au, O +Au , and Be 7,9+Au at the Relativistic Heavy Ion Collider.
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