Measurement of an excess of B→D^(*)τ^−ν_τ decays and implications for charged Higgs bosons

Abstract

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.

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