Dihadron and isolated direct photon-hadron angular correlations are measured in $p$$+$$p$ collisions at $sqrt{s}=510$ 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 $p_{rm out}$ 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 ($p_T^{rm trig}$). The Gaussian widths and root mean square of $p_{rm out}$ are reported as a function of the interaction hard scale $p_T^{rm trig}$ to investigate possible transverse-momentum-dependent evolution differences between the $pi^0$-h$^pm$ and direct photon-h$^pm$ correlations and factorization breaking effects. The widths are found to decrease with $p_T^{rm trig}$, 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.
Download