Performance of High Granularity Calorimeter prototypes for the CMS HL-LHC upgrade in beam test experiments at CERN

Abstract

The CMS collaboration has opted for a High Granularity Calorimeter (HGCAL) to replace the current endcap electromagnetic and hadronic calorimeters in the view of high- luminosity phase of the LHC (HL-LHC). The HL-LHC, expected to start at the end of this decade, aims to accumulate proton-proton collision data corresponding to an integrated luminosity of 3000 fb-1 over a span of ten years, which is ten times more data than the ongoing phase of the LHC. High instantaneous luminosity needed to achieve these goals will result in an average of 140 to 200 proton-proton interactions per bunch crossing. These pose very stringent requirements on radiation tolerance of the endcap detectors as well as their pileup mitigation capabilities. The HGCAL is a silicon and scintillator based sampling calorimeter with unprecedented longitudinal and transverse granularity, which will facilitate efficient particle-flow reconstruction, particle identification, and pileup rejection.The CMS HGCAL collaboration is extensively testing the detector components and its associated electronics in test bench based experiments and in beam test experiments with single particles. A prototype of the electromagnetic and hadronic section of the HGCAL was built and tested along with the CALICE Analogue Hadron Calorimeter (AHCAL) prototype in the beams of single particles at CERN’s Super Proton Synchrotron (SPS) in October 2018. The combined prototype was exposed to the beams of positrons and charged pions with momenta ranging from 20 to 300 GeV/c, and muons of 200 GeV/c. This thesis presents the performance of individual prototype silicon sensor modules as well as construction, com- missioning, calibration of the HGCAL prototype used in the beam test experiments. A first detailed study of performance of combined HGCAL and AHCAL prototype to hadronic showers generated by charged pions using the data collected in October 2018 is reported in this thesis. The results are also compared against simulated hadron showers modeled using GEANT4-based detector simulation framework.