Speaker
Description
This presentation details a study of the prospective measurement of the cross-section times branching ratio for Higgs decaying into two photons, $\sigma(e^{+}e^{-} \rightarrow ZH) \times \mathrm{Br}(H \rightarrow \gamma\gamma)$, at the Circular Electron Positron Collider (CEPC). The analysis is performed at a center-of-mass energy of $\sqrt{s} = 240$ GeV, considering the three dominant $Z$ boson decay channels: $Z \rightarrow q\bar{q}$, $\mu^{+}\mu^{-}$, and $\nu\bar{\nu}$. Using simulated Monte Carlo events corresponding to an integrated luminosity of $21.6~\text{ab}^{-1}$, a combined statistical precision of $3.1\%$ is achieved. Furthermore, we investigate the impact of the electromagnetic calorimeter (ECAL) performance by studying the degradation of the photon energy resolution. Our results indicate that the stochastic term is the dominant factor, and a transition from a Silicon-Tungsten to a glass bar ECAL design significantly improves the energy resolution, thereby enhancing the precision of the $H \rightarrow \gamma\gamma$ measurement.
