Exploring extended scalar sectors with di-Higgs signals: a Higgs EFT perspective

We consider extended scalar sectors of the Standard Model as ultraviolet complete motivations for studying the effective Higgs self-interaction operators of the Standard Model effective field theory. We investigate all motivated heavy scalar models which generate the dimension-six effective operator, vertical bar H vertical bar(6), at tree level and proceed to identify the full set of tree-level dimension-six operators by integrating out the heavy scalars. Of seven models which generate vertical bar H vertical bar(6) at tree level only two, quadruplets of hypercharge Y = 3Y(H) and Y = Y-H, generate only this operator. Next we perform global fits to constrain relevant Wilson coefficients from the LHC single Higgs measurements as well as the electroweak oblique parameters S and T. We find that the T parameter puts very strong constraints on the Wilson coefficient of the vertical bar H vertical bar(6) operator in the triplet and quadruplet models, while the singlet and doublet models could still have Higgs self-couplings which deviate significantly from the standard model prediction. To determine the extent to which the vertical bar H vertical bar(6) operator could be constrained, we study the di-Higgs signatures at the future 100 TeV collider and explore future sensitivity of this operator. Projected onto the Higgs potential parameters of the extended scalar sectors, with 30 ab(-1) luminosity data we will be able to explore the Higgs potential parameters in all seven models.