Genuine Extra Yukawas from Extra Higgs, Implications

Abstract

With a second Higgs doublet, extra Yukawa couplings ${\rho }_{ij}$ generally exist. Baryon Asymmetry of the Universe (BAU) can be accounted for by ${\rho }_{tt}\sim \mathcal{O}(1)$, with first order electroweak phase transition (EWPT) arising from $\mathcal{O}(1)$ Higgs quartic couplings. The latter can explain why the observed $h(125)$ boson so resembles the Standard Model (SM) Higgs: with coupling ${\eta }_6\sim \mathcal{O}(1)$ for two-doublet mixing, the $H$--$h$ mixing angle $\cos \gamma \cong -{\eta }_6{v}^2/(m_H^2-m_h^2)$ is suppressed by the $CP$-even boson mass splitting $m_H^2-m_h^2>\mathrm{few}{v}^2$. The approximate alignment, together with the fermion mass-mixing pattern, controls FCNC Higgs effects at low energy. The picture can be probed by $pp\to tt\bar{c}$, $tt\bar{t}$, i.e. same-sign top and triple-top processes at the LHC.

Comments: 4 pages, 2 figures, presented at Moriond QCD 2018