Centrality categorization and application to physics effects in high-energy d + A collisions

30th Winter Workshop on Nuclear Dynamics

Koop, J.D. Orjuela^1

Department of Physics, University of Colorado, Boulder, 390 UCB Boulder, Boulder

CO

80309-0390, United States^1

关键词: Bias correction;    Bias effects;    Collision systems;    Correction factors;    Glauber models;    Impact-parameter;    Monte Carlo generator;    Strong dependences;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/535/1/012015/pdf
DOI  :  10.1088/1742-6596/535/1/012015

来源: IOP

【 摘 要 】

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 pTdependent for d+Au collisions at √SNN= 200 GeV, yet an order of magnitude larger and strongly pTdependent for p+Pb collisions at √SNN=5.02 TeV. The implications of such corrections are discussed for selected physics observables and effects.