4 Search Results

The Gildener-Weinberg two-Higgs doublet model provides a naturally light and aligned Higgs boson, H = H (125). It has been studied in the one-loop approximation of its effective potential, V₁. An important consequence is that the masses of the model’s beyond the Standard Model (BSM) Higgs bosons (H ',A ,H^±) are bounded by the sum rule (M$$^4_{H'}$$ + M$$^4_A$$ + 2M$$^4_{H^+}$$)^1/4 = 540GeV. Although they are well within reach of the LHC, searches for them have been stymied by large QCD backgrounds. Another consequence is that H is highly aligned, i.e., H – H' mixing is small and H hasmore » only Standard Model couplings. A corollary of this alignment is that commonly pursued discovery modes such as H^', A ↔ W⁺ W^-, Z Z, H Z, and H^± ↔ W ^± Z, W ^±H are beyond the reach of LHC experiments. To assess the accuracy of the sum rule and Higgs alignment, we study this model in two loops. This calculation is complicated by having many new contributions. We present two formulations of it to calculate the H – H ' mass matrix, its eigenvectors H₁, H₂, and the mass M_H2 while fixing M_H1 =125 GeV. They give similar results and are in accord with the one-loop results. Requiring MA = M_H^±, we find 180 GeV ≲ M ^{A ,H±} ≲ 380 – 425 GeV and 550 – 700 GeV ≳ M_H2 ≳ 125 GeV , with M_H2 decreasing as M _{A ,H^±} increase. The corrections to H alignment are below $$\mathscr{O}$$(1%). So, the BSM searches above will remain fruitless. Finding the BSM Higgses requires improved sensitivity to their low masses. We discuss three possible searches for this.« less

There is a surprising connection between the top quark and Higgs alignment in Gildener-Weinberg multi-Higgs doublet models. Were it not for the top quark and its large mass, the coupling of the 125 GeV Higgs boson H to gauge bosons and fermions would be indistinguishable from those of the Standard Model Higgs. The top quark’s coupling to a single Higgs doublet breaks this perfect alignment in higher orders of the Coleman-Weinberg loop expansion of the effective potential. But the effect is still small, ≲O(1%), and probably experimentally inaccessible.

If the Higgs boson H(125)is a composite due to new strong interactions at high energy, it has spin-one partners, ρ_H and a_H, analogous to the ρand a₁ mesons of QCD. These bosons are heavy, their mass determined by the strong interaction scale. The strongly interacting particles light enough for ρ_H and a_H to decay to are the longitudinal weak bosons V_L = W_L, Z_L and the Higgs boson H. These decay signatures are consistent with resonant diboson excesses recently reported near 2TeVby ATLAS and CMS. We calculate σ × BR(ρ_H → VV) = few fb and σ × BR(a_H →more » VH) = 0.5–1fb at √s = 8TeV, increasing by a factor of 5–7 at 13TeV. As a result, other tests of the hypothesis of the strong-interaction nature of the diboson resonances are suggested.« less

In addition to the narrow spin-one resonances ρT , ωT and aT occurring in low-scale technicolor, there will be relatively narrow scalars in the mass range 200 to 600–700 GeV. We study the lightest isoscalar state, σT . In several important respects it is like a heavy Higgs boson with a small vev. It may be discoverable with high luminosity at the LHC where it is produced via weak boson fusion and likely has substantial W+W- and Z0Z0 decay modes.