Precision Timing Studies for the CMS High Granularity Calorimeter Using Multiple Dedicated Timing Layers

Abstract

The Compact Muon Solenoid (CMS) experiment records data from proton-proton collisions at the Large Hadron Collider (LHC) to measure properties of, and probe physics beyond, the Standard Model. The LHC High Luminosity upgrade will increase the number of instantaneous proton-proton collisions. The number of collisions per bunch crossing (pileup) will increase by one order of magnitude, posing an experimental challenge when trying to resolve the collision vertices. The CMS electromagnetic calorimeter (ECAL) is used to detect the energy of electrons and photons flying off from the collision. A possible solution to pileup obfuscation is to equip the new ECAL generation with precision timing capabilities. CMS has proposed a silicon-based High Granularity Calorimeter (HGC) to upgrade its current endcap ECAL. Each HGC layer has a hexagonal honeycomb lattice of pixel detectors. We present results from impinging 8-32 GeV electrons at the Fermilab Test Beam Facility using dedicated timing layers identical to the proposed CMS HGC but with an electronic readout capable of resolving time resolutions below 5 ps. When impinging 32 GeV electrons, we measure the device time resolution to be less than 15 ps and approximately 11 ps when combined with a similar layer positioned further down the beam line.

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