Speaker
Description
Various Beyond-the-Standard-Model theories predict the existence of Heavy Stable Charged Particles (HSCPs), making their search one of the key objectives of the CMS Phase-II upgrade for the High-Luminosity LHC (HL-LHC). Owing to their large masses, HSCP candidates are expected to traverse the detector at velocities significantly lower than those of relativistic muons. Therefore, their flight velocity is a crucial feature distinguishing them from ordinary muons and an important observable for detector-based searches. As a fast-timing and large-area subdetector in the CMS muon system, the upgraded RPC electronics chain is expected to provide precise timing information for time-of-flight (TOF) measurements. This report first estimates the achievable timing performance of the RPC and iRPC system by combining the detector intrinsic time resolution with the TDC quantization uncertainty, and evaluates its impact on particle velocity resolution. The requirements on the data acquisition system raw-data readout window and the trigger coincidence window are then investigated to ensure that delayed HSCP signals across four RPC layers can be fully recorded and matched within the same trigger. To validate the TOF measurement chain, a four-layer cosmic-ray test platform based on the iRPC prototype was constructed at CERN 904, with an enlarged vertical spacing between the third and fourth layers to increase the flight path. After event selection and track-based reconstruction, the reconstructed cosmic-ray velocity distribution is found to be consistent with the expectation for near-light-speed muons. These results indicate that the upgraded CMS RPC electronics can provide sufficient TOF precision and effective local trigger support for HSCP searches.