$B_{s(d)}^0-{\bar{B}}_{s(d)}^0$ 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 $\Delta M_d$ and $\Delta M_s$ 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 $\delta =[0^{\circ },60^{\circ }]$, the upper bound on $\tan \beta$ is $\tan \beta \le 30$ after the inclusion of major theoretical uncertainties; (b) for the case of $\tan \beta \le 20$, a light charged Higgs boson with a mass around 300 GeV is allowed; and (c) the bounds on $\tan \beta$ and $M_H$ are strongly correlated: a smaller (larger) $\tan \beta$ means a lighter (heavier) charged Higgs boson.

Comments: 11 pages, 2 EPS figures, RevTex, new references added