Electroweak multi-higgs production: a smoking gun for the type-I two-higgs-doublet model

Abstract

Extending the Higgs sector of the standard model (SM) by just one additional Higgs doublet field leads to the two-Higgs-doublet model (2HDM). In the type-I 𝑍2-symmetric limit of the 2HDM, all the five new physical Higgs states can be fairly light, 𝒪⁡(100) GeV or less, without being in conflict with current data from the direct Higgs boson searches and the 𝐵-physics measurements. In this Letter, we establish that the new neutral as well as the charged Higgs bosons in this model can all be simultaneously observable in the multi-𝑏 final state. The statistical significance of the signature for each of these Higgs states, resulting from the electroweak (EW) production of their pairs, can exceed 5⁢𝜎 at the 13 TeV high-luminosity Large Hadron collider (HL-LHC). Since the parameter space configurations where this is achievable are precluded in the other, more extensively pursued, 2HDM types, an experimental validation of our findings would be a clear indication that the true underlying Higgs sector in nature is the type-I 2HDM.