Study the effect of beam energy spread and detector resolution on the search for Higgs boson decays to invisible particles at a future e${}^{+}$e${}^{-}$ circular collider

Abstract

We study the expected sensitivity to measure the branching ratio of Higgs boson decays to invisible particles at a future circular \epem collider (FCC-ee) in the process $e^{+}{e}^{-}\to HZ$ with $Z\to {\ell }^{+}{\ell }^{-}$ ($\ell =e$ or $\mu$) using an integrated luminosity of 3.5 ab${}^{-1}$ at a center-of-mass energy $\sqrt{s}=240$ GeV. The impact of the energy spread of the FCC-ee beam and of the resolution in the reconstruction of the leptons is discussed. %Two different detector concepts are considered: a detector corresponding to the CMS reconstruction performances and the expected design of the ILC detector. The minimum branching ratio for a $5\sigma$ observation after 3.5ab${}^{-1}$ of data taking is $1.7\pm 0.1\%(stat+syst)$. The branching ratio exclusion limit at 95\% CL is $0.63\pm 0.22\%((stat+syst))$.

17 pages, submitted to EPJC