Photon - Jet Correlations and Constraints on Fragmentation Functions
Z. Belghobsi, M. Fontannaz, J. -Ph. Guillet, G. Heinrich, E. Pilon, M. Werlen
TL;DR
The paper investigates photon plus jet production in hadronic collisions to constrain two key QCD ingredients: the gluon distribution in the proton and the photon fragmentation function. It uses the NLO Monte Carlo code JETPHOX to analyze photon-jet angular distributions, jet rapidity distributions, and photon fragmentation via z_gamma, across Tevatron and RHIC kinematics. It finds that jet rapidity can probe low-x gluons albeit with scale uncertainties; the angular distribution is sensitive to fragmentation but cancellations reduce sensitivity to isolation cuts; the z_gamma observable at RHIC shows strong fragmentation effects and can differentiate fragmentation sets, with a proposed measurement strategy. Overall, the work demonstrates the potential of photon-jet correlations to tighten fragmentation and PDF constraints and to improve Monte Carlo modeling.
Abstract
We study the production of a large-pT photon in association with a jet in proton-proton collisions. We examine the sensitivity of the jet rapidity distribution to the gluon distribution function in the proton. We then assess the sensitivity of various photon + jet correlation observables to the photon fragmentation functions. We argue that RHIC data on photon-jet correlations can be used to constrain the photon fragmentation functions in a region which was barely accessible in LEP experiments.