Search for doubly-charged Higgs boson production at HERA

A search for the single production of doubly-charged Higgs bosons H±± in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb−1 of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings hel of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength heμ=4παem≃0.3, a lower limit of 141 GeV on the H±± mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling heτ≃0.3, masses below 112 GeV are ruled out.