Status of the CMS pixel detector

Abstract

The tracking detector of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) is an all-silicon device. It is comprised of two sub-detectors. The pixel detector is the inner one, which is surrounded by the strip detector. The pixel detector provides seeds for charged particle tracking and measures the impact parameter of the reconstructed tracks. The impact parameter is essential in the reconstruction of primary interaction and secondary decay vertices. The pixel detector was upgraded in the beginning of 2017, during Run 2 of the LHC. Various interventions have been performed on the detector since then, the latest refurbishment taking place during Long Shutdown 2 (LS2) between 2019 and 2022, right after Run 2. The expected fluence in the innermost layer reaches the expected limit for the sensors after about 250 fb − 1 of integrated luminosity; therefore, this layer was also scheduled to be replaced during LS2. In this paper, we describe the successful refurbishment and recommissioning program and the following relatively smooth data-taking period in the first year of Run 3. Preliminary studies of the performance will be presented along with the verification of the new layer 1 modules in which several weaknesses that were revealed during Run 2 have been fixed.