Evidence for an Excess of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mover accent="true"><mml:mi>B</mml:mi><mml:mo>¯</mml:mo></mml:mover><mml:mo>→</mml:mo><mml:msup><mml:mi>D</mml:mi><mml:mrow><mml:mo stretchy="false">(</mml:mo><mml:mo>*</mml:mo><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mi>τ</mml:mi><mml:mo>−</mml:mo></mml:msup><mml:msub><mml:mover accent="true"><mml:mi>ν</mml:mi><mml:mo>¯</mml:mo></mml:mover><mml:mi>τ</mml:mi></mml:msub></mml:math>Decays

Abstract

Based on the full BABAR data sample, we report improved measurements of the ratios $\mathcal{R}({D}^{(*)})=\mathcal{B}(\overline{B}\ensuremath{\rightarrow}{D}^{(*)}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}})/\mathcal{B}(\overline{B}\ensuremath{\rightarrow}{D}^{(*)}{\ensuremath{\ell}}_{\ensuremath{\ell}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\ell}})$, where $\ensuremath{\ell}$ is either $e$ or $\ensuremath{\mu}$. These ratios are sensitive to new physics contributions in the form of a charged Higgs boson. We measure $\mathcal{R}(D)=0.440\ifmmode\pm\else\textpm\fi{}0.058\ifmmode\pm\else\textpm\fi{}0.042$ and $\mathcal{R}({D}^{*})=0.332\ifmmode\pm\else\textpm\fi{}0.024\ifmmode\pm\else\textpm\fi{}0.018$, which exceed the standard model expectations by $2.0\ensuremath{\sigma}$ and $2.7\ensuremath{\sigma}$, respectively. Taken together, our results disagree with these expectations at the $3.4\ensuremath{\sigma}$ level. This excess cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.