Evidence for an excess of B -> D(*) Tau Nu decays

TL;DR

This paper reports measurements of B meson decays involving tau leptons that exceed Standard Model predictions, suggesting potential new physics beyond current models.

Contribution

The study provides improved measurements of R(D) and R(D*) ratios using BaBar data, showing significant deviations from Standard Model expectations and challenging certain new physics models.

Findings

Measured R(D) and R(D*) ratios exceed Standard Model predictions.

Observed B -> D Tau Nu decay with 6.8 sigma significance.

Results disagree with type II two-Higgs-doublet model predictions.

Abstract

Based on the full BaBar data sample, we report improved measurements of the ratios R(D(*)) = B(B -> D(*) Tau Nu)/B(B -> D(*) l Nu), where l is either e or mu. 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 sigma and 2.7 sigma, respectively. Taken together, our results disagree with these expectations at the 3.4 sigma level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model. We also report the observation of the decay B -> D Tau Nu, with a significance of 6.8 sigma.