##article.return## Measurement of the ratio of the B$_\mathrm{c}^+$ $\to$ J/$ψ$$τ^+ν_τ$ and B$_\mathrm{c}^+$ $\to$ J/$ψ$ $μ^+ν_μ$ branching fractions using three-prong $τ$ lepton decays Download Download PDF