Light charged Higgs boson with dominant decay to a charm quark and a bottom quark and its search at LEP2 and future e + e − colliders

The possibility of a light charged Higgs boson H± that decays predominantly to a charm quark and a bottom quark (cb) and with a mass in the range 80 GeV≤MH±≤90 GeV is studied in the context of a three-Higgs doublet model (3HDM). Searches for this decay at the Large Hadron Collider do not have sensitivity to this mass region at present. It is shown that the searches for H± at LEP2 could be supplemented by either one or two b-tags, which would enable such large branching ratios for H±→cb to be probed in the above mass region. We comment on the possibility of this 3HDM scenario to explain a slight excess in the searches for H± at LEP2, which is best fit by MH± of around 90 GeV, and discuss the prospects for detecting H±→cb decays at future e+e− colliders.