Operational results with the pixelated Time Detector of MEG II experiment during the first year of physics data taking

The MEG II experiment was designed to improve by an order of magnitude the sensitivity of 4.2×10−13 reached by MEG on the branching ratio of the μ+→e+γ decay. The resolution of the positron timing is improved by using a segmented pixelated Timing Counter (pTC) where each counter is read independently. The pTC was commissioned in several engineering runs as well as in the first year of physics run (2021) at the πE5 beam line at PSI. Degradation of time resolution performance is observed and a program of partial upgrading the pTC is ongoing.