Abstract
The Compact Muon Solenoid (CMS) experiment is operating at the Large Hadron Collider (LHC) with proton–proton collisions at 13-TeV center-of-mass energy and at a bunch spacing of 25 ns. Challenging running conditions for CMS are expected after the High-Luminosity upgrade of the LHC (HL-LHC). We review the CMS ECAL crystal calorimeter upgrade and present results from the first test beam studies. Particular challenges at HL-LHC are the harsh radiation environment, the increasing data rates, and the extreme level of pile-up events, with up to 200 simultaneous proton–proton collisions. Precision timing can be exploited to reduce the effect of the pileup. We report on the timing resolution studies performed with test beams. We discuss the new readout and trigger electronics, which must be upgraded due to the increased trigger and latency requirements at the HL-LHC.
Highlights
THE Compact Muon Solenoid Experiment (CMS) electromagnetic calorimeter (ECAL) is made of homogeneous lead tungstate crystals
We review the CMS ECAL crystal calorimeter upgrade and present results from the first test beam studies
The main motivation for barrel electronics upgrade for High-Luminosity upgrade of the LHC (HLLHC) is the increase of CMS Level 1 trigger rate from 150 kHz to 750 kHz and the latency from 6.4 μs to 12.5 μs
Summary
The effect of radiation on lead-tungstate crystals has been analyzed [5]. Even though the main scintillation process is not affected by radiation, electromagnetic and hadronic damages cause transparency loss in the crystals. Defects from gamma radiation are temporary and anneal in room temperature. Transparency loss due to electromagnetic radiation reaches an equilibrium which depends on annealing and dose rate. Hadrons can cause permanent transparency loss in the crystals by melting small volumes and creating fission tracks [7,8,9]. This effect occurs when hadrons above tens of MeV
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