Search For New Physics at BABAR

TL;DR

This paper reports improved measurements of B meson decay ratios involving tau leptons, finding deviations from Standard Model predictions that could hint at new physics but are not consistent with a simple charged Higgs model.

Contribution

The study provides the most precise measurements to date of ${ m R}(D^{(*)})$ ratios, revealing significant deviations from Standard Model expectations and constraining new physics models.

Findings

Ratios exceed Standard Model predictions by 2.0σ and 2.7σ.

Combined deviation from Standard Model is 3.4σ.

Results cannot be explained by a charged Higgs in the type II two-Higgs-doublet model.

Abstract

Using a full BABAR data sample of 426 $fb^{-1}$, we present improved measurements of the ratio ${\cal{R}}(D^{(*)}) = {\cal{B}} (\bar{B} \to D^{(*)}\tau^{-}\bar{\nu}_{\tau})/$ ${\cal{B}} (\bar{B} \to D^{(*)}\ell_{\ell}^{-}\bar{\nu}_{\ell})$, where $\ell$ is either electron or muon. We measure ${\cal{R}}(D) = 0.440 \pm 0.058 \pm 0.042$ and ${\cal{R}}(D^*) = 0.332 \pm 0.024 \pm 0.018$. These ratios exceed the Standard Model predictions by $2.0\sigma$ and $2.7\sigma$, respectively. The results disagree with the Standard Model predictions at the level of $3.4\sigma$. The ratios are sensitive to new physics contributions in the form of a charged Higgs boson. However, the access cannot be explained by a charged Higgs boson in the type II two-Higgs-doublet model.