Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in collisions at = 510 GeV

Adare, A.*; Hasegawa, Shoichi   ; Imai, Kenichi; Nagamiya, Shoji; Sako, Hiroyuki   ; Sato, Susumu  ; Tanida, Kiyoshi   ; PHENIX Collaboration*; 462 of others*

Dihadron and isolated direct photon-hadron angular correlations are measured in collisions at = 510 GeV. Correlations of charged hadrons of GeV/ with mesons of GeV/ or isolated direct photons of GeV/ are used to study nonperturbative effects generated by initial-state partonic transverse momentum and final-state transverse momentum from fragmentation. The nonperturbative behavior is characterized by measuring the out-of-plane transverse momentum component perpendicular to the axis of the trigger particle, which is the high- direct photon or . Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (). The Gaussian widths and root mean square of are reported as a function of the interaction hard scale to investigate possible transverse-momentum-dependent evolution differences between the - and direct photon- correlations and factorization breaking effects. The widths are found to decrease with , which indicates that the Collins-Soper-Sterman soft factor is not driving the evolution with the hard scale in nearly back-to-back dihadron and direct photon-hadron production in collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.