Precision timing with the CMS MIP timing detector

Abstract

The Compact Muon Solenoid detector at the CERN Large Hadron Collider is undergoing anextensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC. In particular, a new timing layer with hermetic coverage up to a pseudo-rapidityof |h|=3 will measure minimum ionizing particles with a time resolution of 30 ps. This MIPTiming Detector will consist of a central barrel region based on LYSO:Ce crystals read out withSiPMs and two end-caps instrumented with radiation-tolerant Low Gain Avalanche Detectors.The precision time information from the MTD will reduce the effects of the high levels of pileupexpected at the HL-LHC and will bring new and unique capabilities to the CMS detector. Thetime information assigned to each track will enable the use of 4D reconstruction algorithms andwill further discriminate interaction vertices within the same bunch crossing to recover the trackpurity of vertices in current LHC conditions. For instance, in the analysis of di-Higgs boson production,a timing resolution of 30-40 ps is expected to improve the effective luminosity by about25% through gains in b-tagging and isolation efficiency. We present motivations for precisiontiming at the HL-LHC and overview the MTD design, while also highlighting specific physics studies benefiting from the improved timing information.