Performance of the CMS High Granularity Calorimeter prototype to charged pion beams of 20–300 GeV/c

Abstract

The upgrade of the CMS experiment for the high luminosity operation of the LHC comprises the replacement of the current endcap calorimeter by a high granularity sampling calorimeter (HGCAL). The electromagnetic section of the HGCAL is based on silicon sensors interspersed between lead and copper (or copper tungsten) absorbers. The hadronic section uses layers of stainless steel as an absorbing medium and silicon sensors as an active medium in the regions of high radiation exposure, and scintillator tiles directly read out by silicon photomultipliers in the remaining regions. As part of the development of the detector and its readout electronic components, a section of a silicon-based HGCAL prototype detector along with a section of the CALICE AHCAL prototype was exposed to muons, electrons and charged pions in beam test experiments at the H2 beamline at the CERN SPS in October 2018. The AHCAL uses the same technology as foreseen for the HGCAL but with much finer longitudinal segmentation. The performance of the calorimeters in terms of energy response and resolution, longitudinal and transverse shower profiles is studied using negatively charged pions, and is compared to GEANT4 predictions. This is the first report summarizing results of hadronic showers measured by the HGCAL prototype using beam test data.

Software compensation for highly granular calorimeters using machine learning

“…𝐾 S is calculated using a algorithm described in ref. [11]. The transformation results in three new spatial coordinates: a hit radius, 𝑅 hit = √︁ (𝐼 hit − CoG 𝐼 ) 2 + (𝐽 hit − CoG 𝐽 ) 2 , measured in cell units; a hit azimuthal angle, 𝜃 hit = arctan2 (𝐽 hit − CoG 𝐽 , 𝐼 hit − CoG 𝐼 ), where arctan2 is the 2-argument arctangent, measured in radians, and a shower-start normalised depth, 𝐾 hit − 𝐾 S , measured in layer indices.…”

Timing performance of the CMS High Granularity Calorimeter prototype

“…In the beam test reported here, the timing performance of a 28-layer electromagnetic calorimeter with a full analog read-out chain with precision timing in each channel was measured. Previous publications have described the construction and the data acquisition system of this prototype calorimeter [3,4], and the energy resolution, linearity, and position and angular resolutions for both positrons and charged pions [5,6].…”

Scintillator Section of the CMS High Granularity Calorimeter Upgrade (HGCAL)

“…Both detector systems are designed to have a signal-to-noise ratio of >3 for minimum ionising particles throughout the detector's lifetime [1]. The scintillator part of the detector was inspired by the CALICE AHCAL [2], a prototype of which was successfully operated in a combined beam test [3] together with a prototype of the silicon section of the HGCAL.…”