CMS High-Granularity Calorimeter for HL-LHC

The CMS experiment at the CERN LHC will be upgraded to accommodate the 5-fold increase in the instantaneous luminosity expected at the High-Luminosity LHC. The increase in instantaneous luminosity will lead to an increase in the number of interactions in each bunch crossing and a significant increase in the total ionising dose and fluence. One part of this upgrade is the replacement of the current endcap calorimeters with a high granularity sampling calorimeter. It will feature unprecedented transverse and longitudinal readout and triggering segmentation for both electromagnetic and hadronic sections. The electromagnetic section and a large fraction of the hadronic section will be based on hexagonal silicon sensors, with the remainder of the hadronic section being based on highly-segmented scintillators with silicon photomultiplier readout. The front-end electronics measures and digitizes the charge deposited in the silicon sensors cells or generated in the silicon photomultipliers and transmits the digitized data to the back-end electronics located in the service cavern. The back-end electronics consist of two main parts; data acquisition system and trigger primitive generator system. This paper describes the overall design of the high granularity sampling calorimeter and its main components, along with system and beam test results during the prototyping phase.