Nonperturbative transverse-momentum-dependent effects in dihadron and direct photon-hadron angular correlations in p + p collisions at √s= 200 GeV

摘要

Dihadron and isolated direct photon-hadron angular correlations are measured in p+p collisions at √s=200 GeV. The correlations are sensitive to nonperturbative initial-state and final-state transverse momenta k_T and j_T in the azimuthal nearly back-to-back region ΔΦ - π. To have sensitivity to small transverse momentum scales, nonperturbative momentum widths of p_(out), the out-of-plane transversemomentum component perpendicular to the trigger particle, are measured. In this region, the evolution of p_(out) can be studied when several different hard scales are measured. These widths are used to investigate possible effects from transverse-momentum-dependent factorization breaking. When accounting for the longitudinal-momentum fraction of the away-side hadron with respect to the near-side trigger particle, the widths are found to increase with the hard scale; this is qualitatively similar to the observed behavior in Drell-Yan and semi-inclusive deep-inelastic scattering interactions, where factorization is predicted to hold. The momentum widths are also studied as a function of center-of-mass energy by comparing to previous measurements at √s=510 GeV. The nonperturbative jet widths also appear to increase with√s at a similar x_T, which is qualitatively consistent to similar measurements in Drell-Yan interactions. Future detailed global comparisons between measurements of processes where transverse-momentum-dependent factorization is predicted to hold and be broken will provide further insight into the role of color in hadronic interactions.