Measurement of the absolute branching fraction for $\hat{I}{›}_c^{+}\to \hat{I}›e^{+}\hat{I}{½}_e$

Abstract

We report the first absolute measurement of the branching fraction of $\hat{I}{›}_c^{+}\to \hat{I}›e^{+}\hat{I}{½}_e$. This measurement is based on 567 pb${}^{-1}$ of $e^{+}{e}^{-}$ annihilation data produced at $\sqrt{s}=4.599$ GeV, which is just above the $\hat{I}{›}_c^{+}\bar{\hat{I}}{›}_c^{-}$ threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be $\mathcal{B}(\hat{I}{›}_c^{+}\to \hat{I}›e^{+}\hat{I}{½}_e)=(3.63\pm 0.38(\mathrm{stat})\pm 0.20(\mathrm{syst}))\%$, representing a more than twofold improvement in precision upon previously published results. As the branching fraction for $\hat{I}{›}_c^{+}\to \hat{I}›e^{+}\hat{I}{½}_e$ is the benchmark for those of other $\hat{I}{›}_c^{+}$ semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.