Calibration & Alignment of the CMS Electromagnetic Calorimeter

The electromagnetic calorimeter (ECAL) of the Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider is a homogenous, scintillating lead tungstate crystal calorimeter, designed to achieve excellent energy resolution. Precise calibration and alignment of the CMS ECAL is crucial for maintaining the excellent ECAL performance required for many physics analyses. To ensure uniformity across the ECAL, a relative inter-calibration is performed across all channels, using a few different methods. The position measurements provided by ECAL are also calibrated relative to the CMS tracker. Since energy deposits in ECAL are the only way to provide position measurements for photons, the ECAL alignment procedure is critical for the measurement of Higgs boson decays to two photons, and is also an important tool to identify and remove electrons misidentified as photons. After an introduction to the characteristics of the CMS ECAL, I will briefly describe the details of the different inter-calibrations methods and their combined performance with CMS Run 2 data. I will also discuss in detail the dedicated ECAL alignment procedure based on matching the positions reconstructed by CMS ECAL and tracker, and I will present the latest results from the ECAL alignment.