Light doubly charged Higgs boson via the WW∗ channel at LHC

The doubly charged Higgs bosons H ± ± searches at the large hadron collider (LHC) have been studied extensively and strong bound is available for H ± ± dominantly decaying into a pair of same-sign di-leptons. In this paper we point out that there is a large cavity in the light H ± ± mass region left unexcluded. In particular, H ± ± can dominantly decay into WW or W W ∗ (For instance, in the type-II seesaw mechanism the triplet acquires a vacuum expectation value around 1 GeV), and then it is found that H ± ± with mass even below 2 m W remains untouched by the current collider searches. Searching for such a H ± ± at the LHC is the topic of this paper. We perform detailed signal and background simulation, especially including the non-prompt t t ¯ background which is the dominant one nevertheless ignored before. We show that such H ± ± should be observable at the 14 TeV LHC with 10–30 fb - 1 integrated luminosity.