Measurement of an excess of B̄→D(*) τ-ν̄τ 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(B̄→Dτ-ν̄τ)/ B(B̄→Dℓ-ν̄ℓ) and R(D*)=B(B̄→D*τ-ν̄τ)/ B(B̄→D*ℓ-ν̄ℓ), 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. © 2013 American Physical Society.