LHC signatures of a generalized Georgi-Machacek model

Abstract

Vector-boson fusion productions of new Higgs bosons decaying into pairs of electroweak gauge bosons (W±W±, WZ, and ZZ) are smoking-gun signature of new Higgs bosons in general, and of the Georgi-Machacek (GM) model in particular. Notably, ATLAS has observed a 3.3σ excess in W±W± at ≈450 GeV and a 2.8σ excess in the WZ channel at ≈375 GeV, while compact muon solenoid reported weaker-than-expected limits at these masses. In this article, we consider a generalized version of the GM model without the custodial SUð2ÞC symmetry in the scalar potential as a minimal model to explain these excesses. In the limit of small mixing among the Higgs bosons, the W±W± and WZ signals can be explained by the doubly and singly charged Higgs bosons originating primarily from the Y ¼ 1 triplet, while respecting the bounds from ZZ searches. Furthermore, the neutral Higgs boson mostly contained in the Y ¼ 0 triplet can account for the (≈4σ) excess at ≈152 GeV in associated diphoton production. Furthermore, the model is consistent with the constraints from vacuum stability and the Standard Model Higgs signal strength measurements, such that it can provide a valid combined explanation for some of the most significant LHC excesses.