Resumen de Measurements of the inclusive isolated-photon and photon-plus-jet production in pp collisions at √s = 13 TeV with the ATLAS detector
This thesis presents various measurements of the di˙erential cross section for isolatedphoton production inclusively and in association with one jet in proton-proton collisions at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. These measurements are sensitive to the parton distribution functions in the proton. In addition, a study of the in situ calibration of the jet energy scale and resolution of jets using photonplus-jet events in proton-proton collisions at a centre-of-mass energy of 13 TeV is also included.
The inclusive isolated-photon di˙erential cross section was measured using a sample of events corresponding to an integrated luminosity of 36.1 fb−1 collected during the 2015 and 2016 data-taking periods. The measurement was performed in four di˙erent regions of the pseudorapidity of the photon as a function of the photon transverse energy. A later measurement was performed using the full integrated luminosity of the ATLAS Run II data of 139 fb−1 , increasing the regions of pseudorapidity of the photon from four to six and measuring the cross section for two di˙erent photon isolation cone sizes. In both measurements, theoretical predictions are found to provide a good description of the data within the experimental and theoretical uncertainties. The production of isolated-prompt photons associated with one jet was studied using 138.4 fb−1 of the ATLAS Run II dataset. The di˙erential cross section was measured as a function of the transverse energy of the photon for di˙erent angular con˝gurations of the photon and the jet. The next-to-leading order perturbative QCD calculations describe adequately the data.
The jet energy scale and resolution were measured using in situ techniques in photonplus-jet events in which the photon and the leading jet transverse momenta are balanced. The jet energy scale (resolution) measurement presented in this dissertation was performed using a sample of events corresponding to an integrated luminosity of 80 fb−1 (58.5 fb−1) collected during the 2015 − 2017 (2018) data-taking periods. The in situ γ+jet corrections to the jet energy scale are at the level of 2% in most of the measured range of the photon transverse momentum, and the uncertainty on the jet energy scale is of the order of 1% for the di˙erent measured con˝gurations. Resolutions at the order of 17% − 24% (4% − 5%) with experimental uncertainties of ≈ 25% − 45% (≈ 35%) are obtained at photon transverse momenta of 25−45 GeV (≈ 1.2 TeV) for the two measured regions of jet rapidity and jet collections
