Nonperturbative-transverse-momentum broadening in dihadron angular correlations in root S-NN=200 GeV proton-nucleus collisions

Abstract

The PHENIX collaboration has measured high-P T dihadron correlations in p + p, p + A1, and p + Au collisions at root 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(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(out) widths, sensitive to fragmentation transverse momentum, show no significant broadening between p + Au, p + A1, and p + p. The away-side nonperturbative p(out) widths are found to be broadened in p + Au when compared to p + p; however, there is no significant broadening in p + A1 compared to p + p collisions. The data also suggest that the away-side p(out) broadening is a function of N-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.