Search for B -> tau nu at Belle

TL;DR

This paper reports a search for the B -> tau nu decay using Belle data, setting an upper limit on its branching ratio due to no significant signal detection.

Contribution

First search for B -> tau nu at Belle with a novel event selection method, establishing an upper limit on the decay's branching ratio.

Findings

No significant evidence for B -> tau nu decay.

Upper limit on Br(B -> tau nu) < 2.9 x 10^-4 at 90% CL.

Method effectively suppresses background in B decay searches.

Abstract

We present a search for the decay B -> tau nu in a 140 fb^-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric B factory. Combinatorial and continuum backgrounds are suppressed by selecting a sample of events with one fully reconstructed B. The decay products of the other side B in the event are analyzed to search for a B -> tau nu decay. We find no significant evidence for a signal and set a 90% confidence level upper limit of Br(B -> tau nu) < 2.9 * 10^-4. All results are preliminary.