| Experiment | Measurement | Reference |
|---|---|---|
| Belle | < \(0.90 \times 10^{-3}\) | PRL 93,051803(2004) |
| BaBar | \([0.22 \pm 0.05\mbox{ (stat)} \pm 0.05\mbox{ (syst)}] \times 10^{-3}\) | PRD 83, 032004 (2011) |
| Average | \(\mathbf{[0.22 \pm 0.07\mbox{ (combined)}] \times 10^{-3}}\) |