Measurements of photon-jet correlations in pp and p+Pb collisions with the ALICE detector at the LHC

Particle correlations are used to study jet energy loss exhibited by quark-gluon plasma (QGP) at the ALICE experiment at the LHC at CERN. I will present γ-hadron, γ-jet, and π⁰-jet correlations of pp and p-Pb taken by the ALICE experiment. The photons used in the γ-hadron study were isolated direct photons, which have few other particles nearby. To separate single photons from pairs of photons from meson decays, I analyze the shape of the energy deposited in the ALICE electromagnetic calorimeter. I used two methods - a deep neural network, and rejecting clusters with higher RMS shower energy along the major ellipse axis.

Correlation functions are normalized by the number of triggers, and conditional yields of hadrons and jets are shown as a function of the difference in azimuthal angle. π⁰-jet and γ-jet correlations are studied with a variety of observables, including a new observable designed to measure a parton’s momentum as a fraction of that of a lead nucleus. The results are compared to event-generators and will eventually be compared with similar results from PbPb, which produce more QGP than p-Pb collisions. We aim to assess the mechanism of jet energy loss in QGP, and constrain the gluon densities in heavy nuclei.