Measurement of the $\ddot{I}„$ lepton polarization and $R(D^{\ast })$ in the decay $\bar{B}\to D^{\ast }\ddot{I}{„}^{-}\bar{\hat{I}}{½}_{\ddot{I}}„$ with one-prong hadronic $\ddot{I}„$ decays at Belle

Abstract

With the full data sample of $772\times 10^6$ $B\bar{B}$ pairs recorded by the Belle detector at the KEKB electron-positron collider, the decay $\bar{B}\to D^{\ast }\ddot{I}{„}^{-}\bar{\hat{I}}{½}_{\ddot{I}}„$ is studied with the hadronic $\ddot{I}„$ decays $\ddot{I}{„}^{-}\to \ddot{I}{€}^{-}\hat{I}{½}_{\ddot{I}}„$ and $\ddot{I}{„}^{-}\to \ddot{I}{}^{-}\hat{I}{½}_{\ddot{I}}„$. The $\ddot{I}„$ polarization $P_{\ddot{I}}„(D^{\ast })$ in two-body hadronic $\ddot{I}„$ decays is measured, as well as the ratio of the branching fractions $R(D^{\ast })=\mathcal{B}(\bar{B}\to D^{\ast }\ddot{I}{„}^{-}\bar{\hat{I}}{½}_{\ddot{I}}„)/\mathcal{B}(\bar{B}\to D^{\ast }{\ell }^{-}\bar{\hat{I}}{½}_{\ell })$, where ${\ell }^{-}$ denotes an electron or a muon. Our results, $P_{\ddot{I}}„(D^{\ast })=-0.38\pm 0.51{(\mathrm{stat})}_{-0.16}^{+0.21}(\mathrm{syst})$ and $R(D^{\ast })=0.270\pm 0.035{(\mathrm{stat})}_{-0.025}^{+0.028}(\mathrm{syst})$, are consistent with the theoretical predictions of the Standard Model. The polarization values of $P_{\ddot{I}}„(D^{\ast })>+0.5$ are excluded at the 90\% confidence level.

17 pages, 11 figures, submitted to Physical Review D