The expected measurement precision of the branching ratio of the Higgs decaying to the di-photon at the CEPC

Abstract

This paper presents the prospects of measuring $\sigma (e^{+}{e}^{-}\to ZH)\times Br(H\to \gamma \gamma )$ in 3 $Z$ decay channels $Z\to q\bar{q}/{\mu }^{+}{\mu }^{-}/\nu \bar{\nu }$ using the baseline detector with $\sqrt{s}=240GeV$ at the Circular Electron Positron Collider (CEPC) . The simulated Monte Carlo events are generated and scaled to an integrated luminosity of 5.6 $a{b}^{-1}$ to mimic the data. Extrapolated results to 20 $a{b}^{-1}$ are also shown. The expected statistical precision of this measurement after combining 3 channels of $Z$ boson decay is 7.7\%. With some preliminary estimation on the systematical uncertainties, the total precision is 7.9\%. The performance of CEPC electro-magnetic calorimeter (ECAL) is studied by smearing the photon energy resolution in simulated events in $e^{+}{e}^{-}\to ZH\to q\bar{q}\gamma \gamma$ channel. In present ECAL design, the stochastic term in resolution plays the dominant role in the precision of Higgs measurements in $H\to \gamma \gamma$ channel. The impact of the resolution on the measured precision of $\sigma (ZH)\times Br(ZH\to q\bar{q}\gamma \gamma )$ as well as the optimization of ECAL constant term and stochastic term are studied for the further detector design.

References in corpus (2)

• Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
• Observation of a new boson at a mass of 125 GeV with the CMS experiment at the LHC

Cited by in corpus (1)

• Probing Neutral Triple Gauge Couplings via $\mathbf{Z\gamma }({\mathbf{\ell }}^{+}{\mathbf{\ell }}^{-}\mathbf{\gamma })$ Production at ${\mathbf{e}}^{+}{\mathbf{e}}^{-}$ Colliders