Nonperturbative transverse momentum broadening in dihadron angular correlations in √(s_NN)=200 GeV proton-nucleus collisions

The PHENIX collaboration has measured high-p_T dihadron correlations in p+p, p+Al, and p+Au collisions at √(s__NN)=200 GeV. The correlations arise from inter- and intra-jet 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 multi-differentially 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+Al, 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+Al 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.