Studies of the misidentification probability of electrons as photons with the CMS experiment in data recorded in 2015

In this thesis the estimation of backgrounds for search analyses with photon final states arising from the misidentification of electrons as photons in the CMS detector is studied. To determine the misidentification probability, events containing a Z boson that decays into two electrons are selected and assigned to two event classes using a tag and probe method. The Z-boson resonance is then fitted with template based probability distributions for signal and background. The method is validated in simulation and the results for the first LHC Run I data recorded by CMS in 2015 are presented.