Crossed two-Higgs-doublet models: Reduction of Yukawa parameters in the low-scale limit of left-right symmetry and other avatars

We present new variants of the two-Higgs-doublet model where all Yukawa couplings with physical Higgs bosons are controlled by the quark mixing matrices of both chiralities, as well as, in one case, the ratio between the two scalar doublets’ vacuum expectation values. We obtain these by imposing approximate symmetries on the Lagrangian which, in one of the cases, clearly reveals the model to be the electroweak remnant of the minimal left-right symmetric model. We also argue for the benefits of the bidoublet notation in the two-Higgs-doublet model context for uncovering new models.

Figure 1

Plot of $\tan \beta$ vs $R=\sqrt{\mathrm{Tr}({\mathrm{\Gamma }}^{†}\mathrm{\Gamma })/\mathrm{Tr}({\mathrm{\Delta }}^{†}\mathrm{\Delta })}$ for randomly generated $\mathrm{\Gamma }$ and $\mathrm{\Delta }$. The shaded region is consistent with the observed quark masses and mixings, in the x2HDM-1 (left) and x2HDM-2 (right). We impose a perturbativity limit of $|{\mathrm{\Gamma }}_{ab}|,|{\mathrm{\Delta }}_{ab}|\le 1$.

Figure 2

Log-log plot of relative branching ratios for the $S$ decay into quark-antiquark pairs, normalized by its branching ratio into a $\overline{b}b$ quark pair, as a function of $\tan \beta$, for the x2HDM-1, for $M_S=M_A=1.5\mathrm{TeV}$. The region for $\tan \beta$ which was excluded in Fig. 1 is intentionally kept out in these plots. The relative branching ratios for $A$ are very similar.