PRD 79, 112003 (2009)

CDF: INSPIRE link

ParameterMeasurement
\(\frac{{\cal{B}} ( B^{-} \to J/\psi \pi^{-} )}{{\cal{B}} ( B^{-} \to J/\psi K^{-} )}\)\([4.86 \pm 0.82\mbox{ (stat)} \pm 0.15\mbox{ (syst)}] \times 10^{-2}\)