Measurements of isolated-photon production inclusively and in association with jets at \boldmath$\sqrt{s}=13$~TeV with the ATLAS detector

Measurements of prompt-photon production at the Large Hadron Collider provide a handle on the gluon density in the proton by means of the Compton scattering and can be used to constrain the gluon density function inside the proton. The constraining power of the measurements can be enhanced if they are combined with measurements at different centre-of-mass energies. The requirement of jets in the final state allows to probe the dynamics of the hard-scattering process by measuring the correlations between the photon and the jets. Measurements of the photon plus one jet cross section as a function of the scattering angle in the centre-of-mass frame are sensitive to the spin of the particle exchanged in the t-channel and thus provide insight into the dominant production mechanism. When two jets are required, the production mechanisms can be studied in detail by selecting different regions of the phase space in which their contributions are enhanced according to whether the photon is the object with the highest or lowest transverse momentum among the three objects considered in the final state. The results of four different analyses at $\sqrt{s} = 13$~TeV are presented, namely the measurement of inclusive isolated-photon cross sections, the ratio of inclusive isolated-photon cross sections at $\sqrt{s} = 13$ and 8 TeV, the measurement of the cross section for isolated-photon plus jet production and the cross-section measurements for isolated-photon plus two jets production. Additionally, the offline data quality inspection and sign off assessment of the Liquid Argon calorimeter is described, as well as the first results of jet energy scale corrections with 2017 data using an in-situ technique with photon plus jet events.