Evidence for an excess of B̄ → D^(*)_τ⁻ ν̅_τ decays

Based on the full BABAR data sample, we report improved measurements of the ratios R(D^( *) = ℬ(B̄→D^( )τ -ν {̄τ}) / ℬ(B̄→D^( )ℓe̅ν ̅ℓ), where ℓ is either e or μ. 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, our 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.