Measurement of an excess of B[over ¯]→D^{(*)}τ^{-}ν[over ¯]_{τ} decays and implications for charged Higgs bosons

Based on the full BABAR data sample, we report improved measurements of the ratios R(D)=B(B¯→Dτ-ν¯τ)/B(B¯→Dℓ-ν¯ℓ) and R(D*)=B(B¯→D*τ-ν¯τ)/B(B¯→D*ℓ-ν¯ℓ), where ℓ refers to either an electron or muon. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure R(D)=0.440±0.058±0.042 and R(D*)=0.332±0.024±0.018, which exceed the standard model expectations by 2.0σ and 2.7σ, respectively. Taken together, the results disagree with these expectations at the 3.4σ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. Kinematic distributions presented here exclude large portions of the more general type III two-Higgs-doublet model, but there are solutions within this model compatible with the results.