Measurements of the branching fraction ratio $\mathcal{B}(\varphi \to {\mu }^{+}{\mu }^{-})/\mathcal{B}(\varphi \to e^{+}{e}^{-})$ with charm meson decays

LHCb collaboration, R. Aaij, A. S. W. Abdelmotteleb +1083

Measurements of the branching fraction ratio $\mathcal{B}(\varphi \to {\mu }^{+}{\mu }^{-})/\mathcal{B}(\varphi \to e^{+}{e}^{-})$ with $D_s^{+}\to {\pi }^{+}\varphi$ and $D^{+}\to {\pi }^{+}\varphi$ decays, denoted $R_{\varphi \pi }^s$ an…