A Search for the rare decay B0 --> tau+tau- at BABAR

TL;DR

This paper reports a search for the rare decay B0 --> tau+tau- using BABAR data, setting an upper limit on its branching fraction due to no observed signal.

Contribution

First search for B0 --> tau+tau- decay at BABAR, providing an upper limit on its branching ratio and testing extensions of the Standard Model.

Findings

No evidence of B0 --> tau+tau- decay found

Upper limit on branching ratio: < 4.1 x 10^-3 at 90% CL

Constraints on new physics models predicting this decay

Abstract

We present the results of a search for the decay B0 --> tau+tau- in a data sample of (232 +- 3) x 10^6 Upsilon(4S) --> BBbar decays using the BABAR detector. Certain extensions of the Standard Model predict measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain B(B0 --> tau+tau-) < 4.1 x 10^-3 at the 90% confidence level.