LAUSR

We investigate the production and decays of doubly-charged Higgs bosons for the Type-II seesaw mechanism at an eþe− collider with two center of mass energies, ffiffiffi s p ¼ 380 GeV and 3 TeV, and analyze the fully hadronic final states in detail. Lower mass ranges can be probed during the 380 GeV run of the collider, while high mass ranges, which are beyond the 13 TeV Large Hadron Collider discovery reach, can be probed with ffiffiffi s p ¼ 3 TeV. For such a heavy Higgs boson, the final decay products are collimated, resulting in fat-jets. We perform a substructure analysis to reduce the background and find that a doublycharged Higgs boson in the mass range 800–1120 GeV can be discovered during the 3 TeV run, with integrated luminosity L ∼ 95 fb−1 of data. For 380 GeV center of mass energy, we find that for the doublycharged Higgs boson in the range 160–172 GeV, a 5σ significance can be achieved with only integrated luminosity L ∼ 24 fb−1. Therefore, a light Higgs boson can be discovered immediately during the run of a future eþe− collider.