Speaker
Description
The recent observations of enhanced particle yields, including 𝐽/𝜓, in high event multiplicity 𝑝+𝑝 collisions at RHIC and LHC suggest possible strong contributions from semi-hard Multi-Parton Interactions (MPI) as well as other final state interactions. These new results challenge not only the traditional “single hard-scattering” pQCD description that is widely used in calculating particle yields in p+p collisions, but also the interpretation of other important observables, such as event centrality in the extreme limit in a small system heavy ion collisions and certain event multiplicity dependent transverse spin asymmetries in polarized 𝑝+𝑝(𝐴) interactions. To gain further insight into particle production mechanisms in hadronic interactions, we have studied the 𝐽/𝜓 yield in the forward (and backward) rapidity in p+p and p+Au collisions as a function of event multiplicity and observed a strong dependence of the 𝐽/𝜓 relative yields vs event multiplicities determined over a broad range of rapidity. The latest findings shade new lights on our understanding of the possible correlations of particle production and event global and/or local activities in hadron-hadron collisions. The latest status of this study using the PHENIX 2015 data will be presented.
