C 99 , 044912 ( 2019 ) Nonperturbative-transverse-momentum broadening in dihadron angular correlations in √ sNN = 200 GeV proton-nucleus collisions

The PHENIX collaboration has measured high-pT dihadron correlations in p+p, p+Al, and p+Au collisions at √sNN=200 GeV. The correlations arise from interand intrajet correlations and thus have sensitivity to nonperturbative effects in both the initial and final states. The distributions of pout, the transversemomentum component of the associated hadron perpendicular to the trigger hadron, are sensitive to initialand final-state transverse momenta. These distributions are measured multidifferentially as a function of xE, the longitudinal momentum fraction of the associated hadron with respect to the trigger hadron. The nearside pout widths, sensitive to fragmentation transverse momentum, show no significant broadening between p+Au, p+Al, and p+p. The away-side nonperturbative pout 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 pout broadening is a function of Ncoll, the number of binary nucleon-nucleon collisions, in the interaction. The potential implications of these results with regard to initialand final-state transverse-momentum broadening and energy loss of partons in a nucleus, among other nuclear effects, are discussed.