Two Top Utilities of Two Higgs Doublets: Electroweak Baryogenesis and Alignment

Abstract

With two Higgs doublets but without any discrete $Z_2$ symmetry to forbid flavor changing neutral Higgs couplings, new top Yukawa couplings $\rho_{tt}$ and $\rho_{tc}$ are allowed and naturally complex. Electroweak baryogenesis is remarkably efficient if both $\rho_{tt}$ (and $\rho_{tc}$) and exotic Higgs quartic couplings are ${\cal O}(1)$. Furthermore, the alignment phenomenon, that the observed 125 GeV boson so closely resembles the Standard Model Higgs boson, emerges naturally. One not only has many new flavor and CPV phenomena (modulo SM-like flavor organization plus alignment), but the exotic Higgs bosons $H^0$, $A^0$ and $H^+$ are necessarily sub-TeV in mass, and LHC search should be readjusted.