Speaker
Description
Jets correlated with isolated photons are a promising channel to study jet quenching in heavy-ion collisions, as photons do not interact strongly and therefore constrain the $Q^2$ of the initial hard scattering. The measurement of isolated single photon production constrains NLO pQCD predictions and PDFs, and isolated photon production in Pb-Pb collisions is sensitive to initial geometrical scaling and modifications of the nucleon structure function in nuclei. We present the isolated photon distributions measured in pp and Pb-Pb collisions and isolated photon-jet correlations measured in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV by the ALICE collaboration. The isolated-photon production is measured in the $12 < p_\mathrm{T} < 60$ GeV/$c$ range in pp collisions and in the $10 < p_\mathrm{T} < 100$ GeV/$c$ for the Pb-Pb collisions. We study correlations of isolated photons above 20 GeV/$c$ with charged-particle jets above 20 GeV/$c$, reconstructed with the anti-$k_{\rm T}$ algorithm. The correlations probe the lowest $p_\mathrm{T}$ range measured so far at LHC energies, and larger modifications due to the QGP are expected in the lower $p_\mathrm{T}$ regime.
