Minoru Tanaka, Ryoutaro Watanabe
Recent experimental results on exclusive semi-tauonic $B$ meson decays, $\bar B\to D^{(*)}\tau\bar\nu$, showing sizable deviations from the standard model prediction, suggest a new physics in which the structure of the relevant weak charged interaction may differ from that of the standard model. We study the exclusive semi-tauonic B decays in a model-independent manner using the most general set of four-Fermi interactions in order to clarify possible structures of the charged current in new physics. It turns out that correlations among observables including tau and $D^*$ polarizations and $q^2$ distributions are useful to distinguish possible new physics operators. Further, we investigate some interesting models to exhibit the advantage of our model-independent analysis. As a result, we find that two Higgs doublet models without tree-level FCNC and the minimal supersymmetric standard model with R-parity violation are unlikely to explain the present experimental data, while two-Higgs-doublet models with FCNC and a leptoquark model are consistent with the data.
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http://arxiv.org/abs/1212.1878
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