Experiment	Measurement	Reference
Belle	< \(3.6 \times 10^{-5}\)	PRD 75, 091102 (2007)
BaBar	< \(1.0 \times 10^{-4}\)	PRD 72 111101(R) (2005)
Average	< \(\mathbf{3.6 \times 10^{-5}}\)