| Experiment | Measurement | Reference |
|---|---|---|
| Belle | < \(1.5 \times 10^{-5}\) | PRL 107, 091803 (2011) |
| BaBar | \([1.5 \pm 0.9\mbox{ (stat)} \pm 0.3\mbox{ (syst)}] \times 10^{-5}\) | PRL 102 132001 (2009) |
| Average | \(\mathbf{[1.5 \pm 0.9\mbox{ (combined)}] \times 10^{-5}}\) |