Cluster time measurement with CEPC calorimeter

TL;DR

This paper presents a timing reconstruction algorithm for highly granular calorimeters, achieving picosecond-level time-of-flight measurements for electromagnetic and hadronic showers, with implications for future collider experiments.

Contribution

The paper introduces a novel timing reconstruction algorithm tailored for HGC calorimeters, demonstrating improved time resolution and quantifying effects of detector configurations.

Findings

Achieves 5-20 ps ToF resolution for EM showers above 1 GeV.

Provides 80-160 ps ToF resolution for hadronic showers above 1 GeV.

Timing resolution improves with increased incident particle energy and optimized detector configurations.

Abstract

We have developed an algorithm dedicated to timing reconstruction in highly granular calorimeters(HGC). The performance of this algorithm is evaluated on an electromagnetic calorimeter (ECAL) with geometries comparable to the electromagnetic compartment (CE-E) of the CMS endcap calorimeter upgrade at HL-LHC and conceptual Particle Flow oriented ECAL's for future Higgs factories. The time response of individual channel is parameterized according to the CMS experimental result. The particle Time-of-Flight (ToF) can be measured with a resolution of $5\sim20 \;\rm{ps}$ for electromagnetic (EM) showers and $80\sim 160 \;\rm{ps}$ for hadronic showers above 1 GeV. The presented algorithm provides comparable reconstruction with the $E_{\mathrm{hit}}^2$ weighting strategy and can significantly improve the time resolution compared to a simple averaging of the fast component of the time spectrum. The effects of three detector configurations are also quantified in this study. ToF resolution depends linearly on the timing resolution of a single silicon sensor and improves statistically with increasing incident particle energy. The timing layers at depth of $6\sim 9$ radiation lengths provide higher timing performance for EM showers. A clustering algorithm that vetoes isolated hits improves ToF resolution.