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Measurement of the $\tau$ lepton polarization and $R(D^*)$ in the decay $\bar{B} \to D^* \tau^- \bar{\nu}_\tau$
- Source :
- Phys. Rev. Lett. 118, 211801 (2017)
- Publication Year :
- 2016
-
Abstract
- We report the first measurement of the $\tau$ lepton polarization $P_\tau(D^*)$ in the decay $\bar{B} \rightarrow D^* \tau^- \bar{\nu}_\tau$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = \mathcal{B}(\bar {B} \rightarrow D^* \tau^- \bar{\nu}_\tau) / \mathcal{B}(\bar{B} \rightarrow D^* \ell^- \bar{\nu}_\ell)$, where $\ell^-$ denotes an electron or a muon, and the $\tau$ is reconstructed in the modes $\tau^- \rightarrow \pi^- \nu_\tau$ and $\tau^- \rightarrow \rho^- \nu_\tau$. We use the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, $P_\tau(D^*) = -0.38 \pm 0.51 {\rm (stat.)} ^{+0.21}_{-0.16} {\rm (syst.)}$ and $R(D^*) = 0.270 \pm 0.035{\rm (stat.)} ^{+0.028}_{-0.025}{\rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model.<br />Comment: 7 pages, 2 figures, submitted to Physical Review Letters; one figure was removed from the first version
- Subjects :
- High Energy Physics - Experiment
Subjects
Details
- Database :
- arXiv
- Journal :
- Phys. Rev. Lett. 118, 211801 (2017)
- Publication Type :
- Report
- Accession number :
- edsarx.1612.00529
- Document Type :
- Working Paper
- Full Text :
- https://doi.org/10.1103/PhysRevLett.118.211801