New limits on tan β for 2HDMs with Z₂ symmetry

In two-Higgs-doublet models with exact Z2 symmetry, putting m_h ≃ 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 β < 8. The constraints from b → sγ and neutral meson mass differences, when superimposed on the unitarity constraints, put a tighter lower limit on tan β depending on m_H+. It has also been shown that larger values of tan β 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.