Following a prediction made in Refs. [1][2][3], this paper focuses on multi-lepton signatures arising from two new hypothetical scalar bosons, H and S, at the Large Hadron Collider (LHC). These two new bosons are an extension to the Standard Model (SM) and interact with the SM Higgs boson, h. We consider two production modes for H, one being gluon fusion and the other being in association with top quarks. The H → Sh decay mode is considered, where leptonic final states are studied. The CP properties of S are characterised by considering effective couplings derived from dimension six operators through SWW vertices. The nature of the S boson is considered in two separate contexts. Firstly in a simplified model, it is considered to have Higgs-like couplings. Secondly, we consider a heavy neutrino model and its interactions with the Z,W and S bosons. The predictions of the models are compared both to ATLAS and CMS results at √ s = 8 and 13 TeV, where appropriate. The data is interpreted using a simplified model where all the signal comes from H → Sh, assuming S to be Higgs-like, m H = 270 GeV and m S = 150 GeV. The combined result yields gives a best fit value for the parameter β g (the strength of the Yukawa coupling of H to top quarks), β 2 g = 1.38 ± 0.22. A number of regions of the phase space are suggested to the experiments for further exploration.

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The simplified modelWithout appealing to any ultraviolet complete theory, 2 the anomaly-free simplified model considered in this article is constructed from a few simple assumptions. Most importantly, 1 Early discrepancies from Run 1 data sets not considered in Ref.[2] include opposite sign di-leptons and missing transverse energy with a full hadronic jet veto (see Ref.[1]) or di-leptons in association with at least one b-jet [3,4], among others (see also Section 4.1 and Section 4.2).2 It can be shown, however, that the assumptions used to construct the model can be mapped consistently onto the parameter space of a 2HDM with an additional singlet scalar [7].