Journal Article Nonperturbative-transverse-momentum effects and evolution in dihadron and direct photon-hadron angular correlations in p+p collisions at √s=510  GeV

PHENIX Collaboration  ,  Chujo, T.  ,  Esumi, S.  ,  Miake, Y.

95 ( 7 )  , p.072002 , 2017-04 , American Physical Society
ISSN:2470-0010
NCID:AA00773624
Description
Dihadron and isolated direct photon-hadron angular correlations are measured in p+p collisions at √s=510  GeV. Correlations of charged hadrons of 0.7<pT<10  GeV/c with π0 mesons of 4<pT<15  GeV/c or isolated direct photons of 7<pT<15  GeV/c 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 pout perpendicular to the axis of the trigger particle, which is the high-pT direct photon or π0. Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (ptrigT). The Gaussian widths and root mean square of pout are reported as a function of the interaction hard scale ptrigT to investigate possible transverse-momentum-dependent evolution differences between the π0−h± and direct photon-h± correlations and factorization breaking effects. The widths are found to decrease with ptrigT, 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 p+p collisions. This behavior is in contrast to Drell-Yan and semi-inclusive deep-inelastic scattering measurements.
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