Higgs boson search significance deformations due to mixed-in scalars

The existence of exotic scalars that mix with the Standard Model (SM) Higgs boson can affect Higgs boson phenomenology in a multitude of ways. We consider two light Higgs bosons with shared couplings to SM fields and with masses close to each other, in the range where the h \to WW \to l \nu l \nu is an important search channel. In this channel, we do not find the dilution of significance of the `SM-like' Higgs boson that is naively expected because of the mixing. This is because of leakage of events from the decay of the other scalar into its signal region. Nevertheless, we show that the broadening of the h\to WW \to l \nu l \nu significance plots of Standard Model Higgs boson searches could indicate the first evidence of the the extra scalar state.