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

Date
2017-04-04
Authors
Adare, Andrew
Apadula, Nicole
Campbell, Sarah
Ding, Lei
Hill, John
Hotvedt, Nels
Lajoie, John
Lebedev, Alexandre
Ogilvie, Craig
Patel, Milap
Perry, Joshua
Rinn, Timothy
Rosati, Marzia
Runchey, Jonathan
Sen, Abhisek
Shaver, Alex
Shimomura, M.
Timilsina, Arbin
Whitaker, Shawn
et al.
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Abstract

Dihadron and isolated direct photon-hadron angular correlations are measured in p + p collisions at root s = 510 GeV. Correlations of charged hadrons of 0.7 < p(T) < 10 GeV/c with pi(0) mesons of 4 < p(T) < 15 GeV/c or isolated direct photons of 7 < p(T) < 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 p(out) perpendicular to the axis of the trigger particle, which is the high-p(T) direct photon or pi(0). Nonperturbative evolution effects are extracted from Gaussian fits to the away-side inclusive-charged-hadron yields for different trigger-particle transverse momenta (p(T)(trig)). The Gaussian widths and root mean square of p(out) are reported as a function of the interaction hard scale p(T)(trig) to investigate possible transverse-momentum-dependent evolution differences between the pi(0)-h(+/-) and direct photon-h(+/-) correlations and factorization breaking effects. The widths are found to decrease with p(T)(trig) , 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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This is an article from Physical Review D 95 (2017): 072002-1, doi:10.1103/PhysRevD.95.072002. Posted with permission.

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