Photon Reconstruction Performance at the CEPC baseline detector

TL;DR

This study evaluates the photon reconstruction capabilities of the CEPC baseline detector, demonstrating its effectiveness in identifying photons, measuring energy resolution, and reconstructing Higgs and neutral pion events, with considerations for detector imperfections.

Contribution

It provides a detailed performance characterization of photon reconstruction at the CEPC baseline detector, including effects of geometry defects and correction methods.

Findings

Achieves 1.7-2.2% Higgs mass resolution in H→γγ

Reconstructs π0 with energies up to 20-30 GeV

Quantifies photon conversion rate and energy resolution

Abstract

The Circular Electron Positron Collider (CEPC) is a proposed Higgs/Z factory. The photon reconstruction is critical to its physics program. We study the photon reconstruction at the CEPC baseline detector, a Particle Flow oriented detector. We characterized the objective performance at both single-photon and di-photon samples. At the single-photon sample, we quantify the photon conversion rate, the differential reconstruction efficiency and energy resolution, and the identification performance. Using di-photon samples, our analysis shows that the CEPC baseline detector reaches a relative mass resolution of 1.7 - 2.2% of the Higgs boson at the $H\to\gamma\gamma$ sample, and can reconstruct the $\pi^0$ with energy as high as 20 - 30 GeV. We also investigate the impact of geometry defects on photon energy resolution and discuss the possible corrections according to the reconstructed photon position.