New limits on $\tan \beta$ for 2HDMs with ${\mathbf{Z}}_2$ symmetry

Abstract

In two-Higgs-doublet models with exact $Z_2$ symmetry, putting $m_h\simeq 125$ GeV at the alignment limit, the following limits on the heavy scalar masses are obtained from the conditions of unitarity and stability of the scalar potential: $m_H,m_A,m_{H^{+}}<1$ TeV and $1/8<\tan \beta <8$. The constraints from $b\to s\gamma$ and neutral meson mass differences, when superimposed on the unitarity constraints, put a tighter lower limit on $\tan \beta$ depending on $m_{H^{+}}$. It has also been shown that larger values of $\tan \beta$ can be allowed by introducing soft breaking term in the potential at the expense of a correlation between $m_H$ and the soft breaking parameter.

Comments: Version accepted in Int J of Mod Phys A