Inclusive and differential $t\bar{t}\gamma$ measurement in the dilepton channel and effective field theory interpretation

Abstract

The production cross section of $t\bar{t}\gamma$ is measured in the dilepton channel using 138 fb$^{-1}$ of proton-proton collision data recorded by the CMS experiment at $\sqrt{s}= 13 $ TeV during the 2016-2018 data-taking period of the CERN LHC. A fiducial phase space is defined at the particle level in which both inclusive and differential results are provided. The $t\bar{t}\gamma$ process is sensitive to EFT operators that modify the top-photon coupling, so that tight constraints on the $c_{tZ}$ and $c_{tZ}^{\mathrm{I}}$ Wilson coefficients can be extracted. Finally, the EFT interpretation is repeated on a combination of this result and a measurement of $t\bar{t}\gamma$ production in the lepton+jets channel.