Advancements in CMS Phase-2 Outer Tracker Module Prototypes Enhance Particle Tracking Capabilities
A new tracking detector is set to be installed as part of the Phase-2 upgrade of the Compact Muon Solenoid (CMS) detector for the high-luminosity Large Hadron Collider (LHC) era. This upgrade includes an Inner Tracker equipped with silicon pixel sensor modules and an Outer Tracker that consists of modules with two parallel stacked silicon sensors. The front-end Application-Specific Integrated Circuits (ASICs) of the Outer Tracker will correlate hits from charged particles in these two sensors, enabling on-module discrimination of transverse momenta (pT). This pT information will be generated at a frequency of 40 MHz and is crucial for the Level-1 trigger decision of the CMS.
Prototypes of the so-called 2S modules were tested at the Test Beam Facility at DESY Hamburg between 2019 and 2020. These prototypes utilized the final front-end ASIC, known as the CMS Binary Chip (CBC), and for the first time, the Concentrator Integrated Circuit (CIC), which facilitates optical readout and on-module power conversion. A total of seven modules were tested, including one assembled with sensors that had been irradiated with protons. A key focus of the tests was to demonstrate the synchronous readout capability of the modules. The results indicated a cluster hit efficiency of approximately 99.75% across all modules tested. Furthermore, the pT discrimination mechanism of the CBC was verified to function effectively in conjunction with the CIC and optical readout, confirming that the performance of the modules meets the operational requirements for the upgraded CMS tracking detector.
These advancements are significant as they enhance the CMS's ability to accurately track particles, which is essential for the ongoing research in particle physics, particularly in understanding fundamental forces and particles in the universe. The findings are detailed in the paper titled "Beam Test Performance Studies of CMS Phase-2 Outer Tracker Module Prototypes" by the Tracker Group of the CMS Collaboration, available on arXiv.