Precision timing calorimetry with the CMS HGCAL

TL;DR

The CMS HGCAL upgrade aims to provide high-precision timing measurements with 30 ps resolution to improve pileup rejection at the HL-LHC, involving advanced electronics, calibration, and reconstruction techniques.

Contribution

This paper introduces the design and testing of the HGCAL's electronics and calibration methods to achieve 30 ps timing resolution in a complex, high-radiation environment.

Findings

Prototype tests demonstrate timing resolution approaching 30 ps.

Electronics design effectively handles high data rates and radiation.

Simulation predicts meeting timing performance goals.

Abstract

The existing CMS endcap calorimeters will be replaced with a High Granularity Calorimeter (HGCAL) for operation at the High Luminosity (HL) LHC. Radiation hardness and excellent physics performance will be achieved by utilising silicon pad sensors and SiPM-on-scintillator tiles with high longitudinal and transverse segmentation. One of the major challenges of the HL-LHC will be the high pileup environment, with interaction vertices spread not only in position, but also in time. In order to efficiently reject particles originating from pileup, precision timing information of the order of 30 ps will be of great benefit. In order to meet such performance goals, the HGCAL will provide timing measurements for individual hits with signals above 12 fC (equivalent to 3-10 MIPs), such that clusters resulting from particles with $p_T$ > 5 GeV should have a timing resolution better than 30 ps. Given the complexity and size of the system, this poses a particular challenge to the readout electronics as well as to the calibration and reconstruction procedures. We present the challenges for the front-end electronics design, results from prototype tests in laboratory and beam environments, as well as anticipated timing performance from simulation.