# Nonperturbative-transverse-momentum broadening in dihadron angular correlations in $\sqrt{{s}_{{}_{NN}}}=200\phantom{\rule{0.16em}{0ex}}\mathrm{GeV}$ proton-nucleus collisions

18 April 2019

Abstract: The PHENIX collaboration has measured high-${p}_{T}$ dihadron correlations in $p+p,p+\mathrm{Al}$, and $p+\mathrm{Au}$ collisions at $\sqrt{{s}_{{}_{NN}}}=200$ GeV. The correlations arise from inter- and intrajet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of ${p}_{\mathrm{out}}$, the transverse-momentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initial- and final-state transverse momenta. These distributions are measured multidifferentially as a function of ${x}_{E}$, the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The near-side ${p}_{\mathrm{out}}$ widths, sensitive to fragmentation transverse momentum, show no significant broadening between $p+\mathrm{Au},p+\mathrm{Al}$, and $p+p$. The away-side nonperturbative ${p}_{\mathrm{out}}$ widths are found to be broadened in $p+\mathrm{Au}$ when compared to $p+p$; however, there is no significant broadening in $p+\mathrm{Al}$ compared to $p+p$ collisions. The data also suggest that the away-side ${p}_{\mathrm{out}}$ broadening is a function of ${N}_{\mathrm{coll}}$, the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to initial- and final-state transverse-momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.

Published in: Physical Review C 99 (2019)