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

TL;DR

This paper investigates how current LHC data constrains the aligned two Higgs doublet model at small , revealing significant bounds from heavy Higgs searches, especially in the diphoton and tau-tau channels.

Contribution

The study provides a detailed analysis of LHC constraints on the small  region of the aligned two Higgs doublet model, highlighting the impact of heavy Higgs search results.

Findings

Heavy Higgs searches exclude <1.5 for 500-600 GeV masses.

Diphoton and tau-tau channels constrain <3 for lighter Higgs masses.

Indirect constraints are weaker than direct search bounds.

Abstract

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. If $m_H \simeq m_A$, the $t\bar{t}$ mode excludes $\tan\beta< 1.5$ for $m_{H,A}=500-600\,$GeV in all four types, and the $\gamma\gamma$ and $\tau^+\tau^-$ modes exclude $\tan\beta < 1-3$ ($\tan\beta < 3-10$) for $m_{H,A}=120-340\,$GeV in Type I, II, and Y (Type X).