$B^0_{s(d)} - \bar{B}^0_{s(d)} $ mixing and new physics effects in a top quark two-Higgs doublet model

Abstract

We calculate the new physics contributions to the neutral $B_d^0$ and $B_s^0$ meson mass splitting $ΔM_d$ and $ΔM_s$ induced by the box diagrams involving the charged-Higgs bosons in the top quark two-Higgs doublet model (T2HDM). Using the precision data, we obtain the bounds on the parameter space of the T2HDM: (a) for fixed $M_H=400$ GeV and $δ=[0^\circ,60^\circ]$, the upper bound on $\tanβ$ is $\tan β\leq 30$ after the inclusion of major theoretical uncertainties; (b) for the case of $\tanβ \leq 20$, a light charged Higgs boson with a mass around 300 GeV is allowed; and (c) the bounds on $\tanβ$ and $M_H$ are strongly correlated: a smaller (larger) $\tanβ$ means a lighter (heavier) charged Higgs boson.