Expected $H\to\mu^{+}\mu^{-}$ measurement precision with $e^{+}e^{-}\to Z(q\bar{q})H$ production at the CEPC

Abstract

A search for the dimuon decay of the Standard Model Higgs boson is performed using the Monte Carlo simulated events to mimic data corresponding to an integrated luminosity of 5.6 ab$^{-1}$ collected with the Circular Electron-Positron Collider detector in $e^{+}e^{-}$ collisions at $\sqrt{s}=240$ GeV. The paper studies $e^{+}e^{-}\to ZH,\,Z\to q\bar{q},\,H\to\mu^{+}\mu^{-}$ process, and the expected significance considering only the data statistical uncertainty over the background-only hypothesis for a Higgs boson with a mass of 125 GeV is found to be 6.1$\sigma$, corresponding to the precision of 19%. The systematic impacts from the background Monte Carlo statistical fluctuations are estimated to be negligible. The dependence of the measurement accuracy on the muon momentum resolution of the CEPC detector has been investigated. It is found that the muon momentum resolution has to be better than 204 MeV to discover the $H\to\mu\mu$ process at the nominal integrated luminosity. And if the resolution is 100% worse than the designed parameter, the integrated luminosity is needed to be greater than 7.2 ab$^{-1}$ to reach 5$\sigma$ significance.