Measurement of the branching fractions for $B^0\to D_s^{\ast +}\ddot{I}{€}^{-}$ and $B^0\to D_s^{\ast -}{K}^{+}$ decays

Abstract

We present a study of $B^0\to D_s^{\ast +}\ddot{I}{€}^{-}$ and $B^0\to D_s^{\ast -}{K}^{+}$ decays based on a sample of $657\times 10^6$ $B\bar{B}$ events collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We measure the branching fractions to be $\mathcal{B}(B^0\to D_s^{\ast +}\ddot{I}{€}^{-})=(1.75\pm 0.34\pm 0.17\pm 0.11)\times 10^{-5}$ and $\mathcal{B}(B^0\to D_s^{\ast -}{K}^{+})=(2.02\pm 0.33\pm 0.18\pm 0.13)\times 10^{-5},withsignificancesof6.1and8.0standarddeviations,respectively.Thefirstuncertaintyisstatistical,thesecondisduetotheexperimentalsystematics,andthethirdisfromuncertaintiesinthe$D_s^+$decaybranchingfractions.Fromourmeasurements,weobtainthemostprecisedeterminationsofarof$R_{D^*π}$,where$R_{D^*π}$istheratiobetweenamplitudesofthedoublyCabibbo-suppresseddecay$B^0 \to D^{*+}π^-$andtheCabibbofavored$B^0 \to D^{*-}π^+$ decay.

6 pages, 2 figures, 2 tables. Submitted to PRD (RC)