Experiment	Measurement	Reference
Belle	< \(2.0 \times 10^{-5}\)	PRD 71, 091107(R)(2005)
BaBar	< \(0.13 \times 10^{-4}\)	PRD 71 091103 (2005)
Average	< \(\mathbf{1.3 \times 10^{-5}}\)