Multi-Lepton Events at H1 and Search for Doubly-Charged Higgs Bosons

Events with two or more leptons (electrons or muons) with high transverse momentum are measured in electron-proton collisions at HERA using the data sample collected in the period 1994-2005. Multi-lepton events at high transverse momenta are of special interest as these signature might reveal new physics beyond the Standard Model. An example is the single production of doubly-charged Higgs bosons $H^{\pm \pm}_{L,R}$, which couple to leptons of the $i^\prime$th and $j^\prime$th generation via Yukawa couplings $h^{L,R}_{ij}$. Results from a search for doubly-charged Higgs bosons in the decays into electrons, muons and taus are presented using data taken in the period 1994-2000. No evidence for doubly-charged Higgs production is found and we derive limits on the $h_{ee}^{L,R}$ and $h_{e \mu}^{L,R}$ Yukawa couplings as a function of the $H^{\pm\pm}_{L,R}$ mass.