Experiment
Measurement
Reference
LHCb
< \(1.9 \times 10^{-7}\)
PRD 88, 072005 (2013)
Belle
< \(9.4 \times 10^{-7}\)
PRD 78:011106,2008
BaBar
< \(0.9 \times 10^{-5}\)
PRL 91 071801 (2003)
Average
< \(\mathbf{1.9 \times 10^{-7}}\)
