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 WW* (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 2m(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) over bar 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.