Precision Timing with the CMS MIP Timing Detector

The Compact Muon Solenoid (CMS) detector at the CERN Large Hadron Collider (LHC) is undergoing an extensive Phase II upgrade program to prepare for the challenging conditions of the High-Luminosity LHC (HL-LHC). A new timing layer is designed to measure minimum ionizing particles (MIPs) with a time resolution of ~30ps and hermetic coverage up to a pseudo-rapidity of $\vert \eta \vert$ = 3. This MIP Timing Detector (MTD) will consist of a central barrel region based on LYSO Ce crystals read out with SiPMs and two end-caps instrumented with radiation-tolerant Low Gain Avalanche Detectors (LGADs). The precision time information from the MTD will reduce the effects of the high levels of pile-up expected at the HL-LHC and will bring new and unique capabilities to the CMS detector. The time information assigned to each track will enable the use of 4D-vertexing which will render a 5-fold pile-up reduction thus recovering the current conditions. Precision timing will also enable new time-based isolations and improved b-tagging algorithms. All of this translates into a ~20\% gain in effective luminosity when looking at di-Higgs boson events decaying to a pair of b-quarks and two photons. We present the current status and ongoing R and D of the MTD, including implications on the physics reach at the HL-LHC and test beam results.