Experiment	Measurement	Reference
Belle	< \(1.8 \times 10^{-5}\)	PRL 90 141802 (2003)
BaBar	\([0.0 \pm 0.5\mbox{ (stat)} \pm 0.3\mbox{ (syst)}] \times 10^{-5}\)	PRD 74 (2006) 031101
Average	\(\mathbf{[0.0 \pm 0.6\mbox{ (combined)}] \times 10^{-5}}\)