A Measurement of $\mathcal{B}(D_s\to \varphi l^{+}\nu )/calB(D_s\to \varphi {\pi }^{+})$

The CLEO Collaboration

Using the CLEO~II detector at CESR, we have measured the ratio of branching fractions $\mathcal{B}(D_s^{+}\to \varphi e^{+}\nu )/\mathcal{B}(D_s^{+}\to \varphi {\pi }^{+})=0.54\pm 0.05\pm 0.04$. We use this meas…