High p_T Direct Photon and pi^0 Triggered Azimuthal Jet Correlations in sqrt(s)=200 GeV p+p Collisions

TL;DR

This study investigates jet fragmentation in high-energy proton-proton collisions using correlations of high pT photons and pi^0 mesons with charged hadrons, providing insights into partonic transverse momentum and fragmentation functions.

Contribution

It introduces a detailed analysis of jet correlations with direct photons and pi^0 mesons, comparing experimental data to models and global fits, highlighting the dominance of quark-gluon Compton scattering.

Findings

The direct photon-associated hadron spectrum matches quark-gluon Compton scattering predictions.

No significant fragmentation photon correlated production observed.

The partonic transverse momentum kT is quantified through model comparison.

Abstract

Correlations of charged hadrons of 1 < pT < 10 GeV/c with high pT direct photons and pi^ 0 mesons in the range 5 <pT < 15 GeV/c are used to study jet fragmentation in the photon+jet and di-jet channels, respectively. The magnitude of the partonic transverse momentum, kT, is obtained by comparing to a model incorporating a Gaussian kT smearing. The sensitivity of the associated charged hadron spectra to the underlying fragmentation function is tested and the data are compared to calculations using recent global fit results. The shape of the direct photon-associated hadron spectrum as well as its charge asymmetry are found to be consistent with a sample dominated by quark-gluon Compton scattering. No significant evidence of fragmentation photon correlated production is observed within experimental uncertainties.