Speaker
Description
Proton-ion collisions at the LHC and RHIC have yielded unexpected trends, notably in measurements of jet nuclear modification factors as a function of event activity (EA). Recent preliminary measurements from STAR in p+Au collisions at $\sqrt{s_{{\rm NN}}}=200$ GeV demonstrate inherent correlations between high-$Q^{2}$ parton scatterings and EA measured at backward (Au-going) rapidities or underlying event (UE) at mid-rapidity. The measurements at STAR disfavor jet quenching as an explanation for the suppression of jet yield observed in high-EA collisions. This leads to an opportunity to probe the early stages of the proton ion collisions. In this talk, we show correlations of backward-rapidity EA with mid-rapidity UE, as well as measurements of EA-dependent modifications to charged hadron spectra and jets. In particular, we present measurements of the UE for various EA selections and discuss its kinematic dependence on jet pseudorapidity ($\eta$) and transverse momentum ($p_{{\rm T}}$) as a means of examining the correlation between initial hard scatterings and soft processes. We also investigate the EA dependence of high-$p_{{\rm T}}$ hadron and jet properties---including fully corrected ungroomed and SoftDrop groomed jet substructure observables---to study the impact of initial and final state effects.
| In-person participation | No |
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