Undeniably, the electrons and the photons play crucial roles in a wide range of analyses at the LHC, including precision physics and searches for physics beyond the Standard Model. The final states of 2 photons and 4 leptons were two of the search channels which saw the first signs of the Higgs boson during Run 1 of the LHC. In this talk, I will give an overview of the reconstruction and identification of electrons and photons in the electromagnetic calorimeter of the CMS experiment, their performance in Run 2 and the improvements planned for Run 3. During the high-luminosity era of the LHC, the endcap calorimeter will be replaced by the High Granularity Calorimeter. There have been test beam activities at CERN during 2016-2018 to test a prototype of this detector. I will discuss how the shower shape properties of the same electrons and photons can change in such a sampling calorimeter. Photons detected in an event can come from non-collision sources and can be a huge background to various searches. We have beam halo monitors to detect such a background. I will discuss their working principle and the plans for Run 3.
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