First Observation of the Hadronic Transition ϒð4SÞ → ηhbð1PÞ and New Measurement of the hbð1PÞ and ηbð1SÞ Parameters

Abstract

Using a sample of 771.6 × 10^6 Upsilon(4S) decays collected by the Belle experiment at the KEKB e+e- collider, we observe, for the first time, the transition with the branching fraction of $\bar{B} \to D^{(\ast)} \tau^- \bar{\nu}_\tau$ relative to $\bar{B} \to D^{(\ast)} \ell^- \bar{\nu}_\ell$ decays with hadronic tagging at Belle.