Search for the decay B^0 --> gamma-gamma

TL;DR

This paper reports a new upper limit on the rare decay B^0 to gamma gamma, using data from the BABAR experiment, significantly improving previous constraints on this decay mode.

Contribution

The study provides the most stringent upper limit to date on the branching fraction of B^0 to gamma gamma decay, based on analysis of BABAR data.

Findings

Established an upper limit of 1.7 x 10^-6 on the branching fraction.

Analyzed 21.3 million B meson decays at the Upsilon(4S) resonance.

Observed one event in the signal region, consistent with background expectations.

Abstract

We present a limit on the branching fraction for the decay $B^0 \to \gamma \gamma$ using data collected at the $\Upsilon(4S)$ resonance with the BABAR detector at the PEP-II asymmetric--energy $e^+e^-$ collider. Based on the observation of one event in the signal region, out of a sample of $21.3 \times 10^6$ $e^+e^- \to \Upsilon(4S) \to B\bar B$ decays, we establish an upper limit on the branching fraction of ${\cal B}(B^0 \to \gamma \gamma) < 1.7 \times 10^{-6}$ at the 90% confidence level. This result substantially improves upon existing limits.