Abstract
The talk will focus on the recent results from the ATLAS and CMS collaborations on measurements of top quark production in association with photons, in particular tt+$\gamma$, using Run 2 LHC data. These analyses probe the electromagnetic coupling of the top quark, and are interesting also from the modelling perspective, due to the challenges related to simulating this process beyond the leading order.
The CMS result [arxiv.org:2511.01995] comprises inclusive and differential measurements of the tt+$\gamma$ cross section, as well as ratios between the tt+$\gamma$ and tt cross sections. The experimental methods used to derive these results will be discussed, including the data-driven background determination and the statistical interpretation. These measurements are compared to different modelling options as well as to fixed order predictions. We will discuss the differences and difficulties arising from these predictions regarding the photon isolation and the top-quark modelling in the presence of photons.
Other related recent results, such as the ATLAS observation of tt+$\gamma\gamma$ [arxiv:2506.05018] and the CMS tq+$\gamma$ and tt+$\gamma$ [CMS-PAS-TOP-25-003] will also be briefly shown.
Speakers