Measurement of an excess of ¯B → D(*)τ−¯ντ 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 → D τ − ¯ ν τ ) / B ( ¯¯¯ B → D ℓ − ¯ 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 2.0 σ and 2.7 σ , respectively. Taken together, the results disagree with these expectations at the 3.4 σ 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.