PRD 87, 11( 2013) 112012

LHCb: INSPIRE

ParameterMeasurement
\(\frac {{\cal{B}} (B_c^- \to J/\psi D_s^-)} {{\cal{B}} (B_c^- \to J/\psi \pi^-)} \)\([2.90 \pm 0.57\mbox{ (stat)} \pm 0.24\mbox{ (syst)}]\)