Extended Higgs sector of 2HDM with real singlet facing LHC data

Abstract

We study the phenomenology of the two Higgs doublet model with a real singlet scalar S (N2HDM). The model predicts three CP-even Higgses h1 , 2 , 3, one CP-odd A and a pair of charged Higgs. We discuss the consistency of the N2HDM with theoretical as well as with all available experimental data. In contrast with previous studies, we focus on the scenario where h2 is the Standard Model (SM) 125 GeV Higgs, while h1 is lighter than h2 which may open a window for Higgs to Higgs decays. We perform an extensive scan into the parameter space of N2HDM of type I and explore the effect of the singlet-doublet admixture. We found that a large singlet-doublet admixture is still compatible with the recent Higgs data from LHC. Moreover, we show that h1 could be quasi-fermiophobic and would decay dominantly into two photons. We also study in details the consistency of the non-detected decay of h2→ h1h1 with LHC data followed by h1→ γγ which leads to four photons final state at LHC: pp→ h2→ h1h1→ 4 γ. Using the results of null searches of multi-photons carried by the ATLAS collaboration, we have found that a large area of the parameter space is still allowed. We also demonstrate that various neutral Higgs of the N2HDM could have several exotic decays.