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

TL;DR

This study analyzed high transverse momentum multi-lepton events in electron-proton collisions at HERA to search for signs of doubly-charged Higgs bosons, setting limits on their couplings and mass due to no observed evidence.

Contribution

First search for doubly-charged Higgs bosons in multi-lepton events at HERA, establishing new limits on Yukawa couplings and mass.

Findings

No evidence for doubly-charged Higgs production.

Limits set on Yukawa couplings as a function of Higgs mass.

Constraints improve previous bounds in certain parameter regions.

Abstract

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.