Measurement of the branching fraction of $D^{+}\to \ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„$

Abstract

By analyzing $e^{+}{e}^{-}$ collision data with an integrated luminosity of 7.9~fb${}^{-1}$ collected with the BESIII detector at the center-of-mass energy of 3.773~GeV, the branching fraction of $D^{+}\to \ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„$ is determined as $\mathcal{B}=(9.9\pm 1.1_{\mathrm{stat}}\pm 0.5_{\mathrm{syst}})\times 10^{-4}$. Taking the most precise result $\mathcal{B}(D^{+}\to \hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)=(3.981\pm 0.079_{\mathrm{stat}}\pm 0.040_{\mathrm{syst}})\times 10^{-4}$, we determine $R_{\ddot{I}„/\hat{I}¼}=\hat{I}“(D^{+}\to \ddot{I}{„}^{+}\hat{I}{½}_{\ddot{I}}„)/\hat{I}“(D^{+}\to \hat{I}{¼}^{+}\hat{I}{½}_{\hat{I}}¼)=2.49\pm 0.31$, achieving a factor of two improvement in precision compared to the previous BESIII result. This measurement is in agreement with the standard model prediction of lepton flavor universality within one standard deviation.