The CMS High-Granularity Calorimeter for Operation at the High-Luminosity LHC

TL;DR

The CMS High-Granularity Calorimeter for the HL-LHC is designed with unprecedented segmentation and timing capabilities to improve particle detection, pileup rejection, and energy resolution in the challenging high-luminosity environment.

Contribution

This paper introduces the design and expected performance of the novel high-granularity calorimeter for CMS, featuring advanced segmentation and timing for HL-LHC upgrades.

Findings

Enhanced pileup rejection due to fine segmentation

Improved energy resolution with high-precision timing

Successful integration of silicon sensors and scintillators

Abstract

The High Luminosity LHC (HL-LHC) will integrate 10 times more luminosity than the LHC, posing significant challenges for radiation tolerance and event pileup on detectors, especially for forward calorimetry, and hallmarks the issue for future colliders. As part of its HL-LHC upgrade program, the CMS collaboration is designing a High Granularity Calorimeter to replace the existing endcap calorimeters. It features unprecedented transverse and longitudinal segmentation for both electromagnetic (ECAL) and hadronic (HCAL) compartments. This will facilitate particle-flow calorimetry, where the fine structure of showers can be measured and used to enhance pileup rejection and particle identification, whilst still achieving good energy resolution. The ECAL and a large fraction of HCAL will be based on hexagonal silicon sensors of 0.5 to 1 cm$^2$ cell size, with the remainder of the HCAL based on highly-segmented scintillators with SiPM readout. The intrinsic high-precision timing capabilities of the silicon sensors will add an extra dimension to event reconstruction, especially in terms of pileup rejection. An overview of the HGCAL project is presented, covering motivation, engineering design, readout and trigger concepts, and expected performance.