Test beam studies of precision timing with the upgraded CMS electromagnetic calorimeter

The electromagnetic calorimeter (ECAL) of the Compact Muon Solenoid Experiment (CMS) is a homogeneous scintillating crystal calorimeter designed to measure the energies of electrons and photons at the Large Hadron Collider (LHC) with excellent resolution. The CMS ECAL will be upgraded to meet the challenging requirements of the High-Luminosity upgrade of the LHC (HL-LHC). Particular challenges at the HL-LHC are the harsh radiation environment, the increasing data rates, and the extreme level of pile-up events, with up to 200 simultaneous proton-proton collisions. We will present test beam studies of the new readout electronics, which must be upgraded due to the increased trigger and latency requirements at the HL-LHC. In particular, we will focus on test beam studies of the timing resolution with the upgraded CMS ECAL readout electronics, which will be around 30 ps for high energy photons and electrons.