Electroweak multi-Higgs production: a smoking gun for the Type-I 2HDM

Extending the Higgs sector of the Standard Model (SM) by just one additional Higgs doublet field leads to the 2-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 article, we establish that the new neutral as well 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 Electro-Weak (EW) production of their pairs, can exceed 5σ at the 13\,TeV High-Luminosity Large Hadron Collider (HL-LHC) with 3000\,fb−1 integrated luminosity. 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.