Explaining B->D\tau\nu, B->D*\tau\nu and B->\tau\nu in a 2HDM of type III

Abstract

Recently, the BaBar collaboration reported first evidence for new physics in B->D\tau\nu and B->D*\tau\nu. Combining both processes the significance is 3.4\sigma. This result cannot be explained in a two Higgs doublet model of type II. Furthermore, the CKMfitter group finds a 2.9\sigma discrepancy between the Standard Model prediction for Br[B->\tau\nu] (using Vub from a global fit to the unitary triangle) and the measurements of the B factories. Altogether, these measurements are strong indications for physics beyond the SM in B meson decays to taus. We show that in a two Higgs doublet model of type III it is possible to simultaneously explain \bdtau and \bdstau using a single free parameter \epsilon^u_32. Also Br[B->\tau\nu] can be brought into agreement with experiment using \epsilon^u_31. Furthermore, for Higgs (A^0, H^0, H^+) masses around 500 GeV, as suggested by recent CMS results, all bounds from FCNC processes are satisfied and B->D\tau\nu, B->D*\tau\nu and B->\tau\nu can be explained without a significant degree of fine-tuning.

Comments: 5 pages, 3 figures, version accepted for publication in PRD