| Experiment | Measurement | Reference |
|---|---|---|
| BaBar | < \(0.36 \times 10^{-4}\) | PRL 94 171801 (2005) (superseded) |
| BaBar | \([6.6 \pm 1.8\mbox{ (stat)} \pm 0.5\mbox{ (syst)}] \times 10^{-5}\) | PRL 102 132001 (2009) |
| Average | \(\mathbf{[6.6 \pm 1.9\mbox{ (combined)}] \times 10^{-5}}\) |