Gigantic diphoton rate of heavy Higgs bosons in the aligned two Higgs doublet models with small $\tan\beta$

Understand

We study the implications of the LHC heavy neutral Higgs search data on the aligned two Higgs doublet model with softly broken $Z_2$ symmetry.

• When $\tan\beta$ is small, the gluon fusion production of the heavy CP-even scalar $H^0$ or the CP-odd scalar $A^0$ becomes large enough to constrain the model by the current $\gamma\gamma$, $\tau^+\tau^-$, and $t\bar{t}$ data.
• By reinvestigating this small $\tan\beta$ region, we find that the indirect constraints like $\Delta\rho$, $b\to s \gamma$, $\Delta M_{B_d}$, $R_b$, $\epsilon_K$, and the perturbativity of running top Yukawa coupling are rather weak to be $\tan\beta > 0.5$.
• The current heavy Higgs search results are shown to put more significant bounds.