Determination of Background from Misreconstructed Electrons in $t\overline{t}\gamma$ Single Lepton Channel at the $\sqrt{s}=13$ TeV with $139$ fb$^{-1}$ of ATLAS Data

A measurement of electron-to-photon fake rate using $139 $fb$^{-1}$ of $pp$ collisions collected by the ATLAS detector in 2015 to 2018 is presented. The $e\rightarrow\gamma$ fake rate, a fraction of $Z\rightarrow e^+e^-$ events is reconstructed as $Z\rightarrow e\gamma$ can be estimated from $Z$ to 2 body decays due to the misidentification. An excess of the $e\gamma$ final state with an invariant mass close to $Z$-mass is a clear symptom to be observed in the data, and compared to the simulation results. A measurement of the probability of electrons to be misidentified as photons ($e\rightarrow\gamma$), referred to as fake rate, using the 139 fb$^{-1}$ of $pp$ collisions data collected by the ATLAS detector from 2015 to 2018. The method for the measurement of the fake rate in data, using pure electrons from the $Z$-boson 2 body decay, called tag-and-probe, is presented. The results are presented as functions of kinematic variables in order to show effects on the detector performance. In addition, the fake rates calculated separately for converted and unconverted photons.