Measurement of B -> D*- tau+ nu and B -> h(*) nu nubar Decays at Belle

TL;DR

This paper reports the first observation of B0 -> D*- tau+ nu decay with a 5.2 sigma significance and sets new upper limits on several rare B -> h(*) nu nubar decays using data from the Belle detector.

Contribution

The study provides the first measurement of B0 -> D*- tau+ nu branching fraction and improved constraints on B -> h(*) nu nubar decays, enhancing understanding of rare B meson decays.

Findings

Observation of B0 -> D*- tau+ nu with 5.2 sigma significance

Measured branching fraction of B0 -> D*- tau+ nu as 2.02 +0.40/-0.37%

Set more stringent upper limits on B -> h(*) nu nubar decays

Abstract

We report an observation of the decay B0 -> D*- tau+ nu and a search for the rare decays B -> h(*) nu nubar\ove, where h(*) stands for a light meson. A data sample of 535 million BBbar pairs collected with the Belle detector at the KEKB e+e- collider is used. We find a signal with a significance of 5.2 standard deviations on B0 -> D*- tau+ nu and measure the branching fraction to be 2.02 +0.40/-0.37 (stat.) +- 0.37 (syst.)%. No significant signal is observed for B -> h(*) nu nubar decays and we set upper limits on the branching fractions at 90% confidence level. The limits on B0 -> K*0 nu nubar and B+ -> K+ nu nubar decays are more stringent than the previous constraints, while the first searches for B0 -> K0 nu nubar, pi0 nu nubar, rho0 nu nubar, phi nu nubar and B+ -> K*+ nu nubar, rho+ nu nubar are presented.