Study of $\psi (3770)$ decaying to Baryon anti-Baryon Pairs

Abstract

To study the decays of $\psi (3770)$ going to baryon anti-baryon pairs ($B\bar{B}$), all available experiments of measuring the cross sections of $e^{+}{e}^{-}\to B\bar{B}$ at center-of-mass energy ranging from 3.0 GeV to 3.9 GeV are combined. To relate the baryon octets, a model based on the SU(3) flavor symmetry is used and the SU(3) breaking effects are also considered. Assuming the elctric and magnetic form factors are equal ($|G_E|=|G_M|$), a global fit including the interference between the QED process and the resonant process is performed. The branching fraction of $\psi (3770)\to B\bar{B}$ is determined to be $(2.4\pm 0.8\pm 0.3)\times 10^{-5}$, $(1.7\pm 0.6\pm 0.1)\times 10^{-5}$, $(4.5\pm 0.9\pm 0.1)\times 10^{-5}$, $(4.5\pm 0.9\pm 0.1)\times 10^{-5}$, $(2.0\pm 0.7\pm 0.1)\times 10^{-5}$, and $(2.0\pm 0.7\pm 0.1)\times 10^{-5}$ for $B=p,\Lambda ,{\Sigma }^{+},{\Sigma }^0,{\Xi }^{-}$ and ${\Xi }^0$, respectively, where the first uncertainty is from the global fit and the second uncertainty is the systematic uncertainty due to the assumption $|G_E|=|G_M|$. They are at least one order of magnitude larger than a simple scaling of the branching fraction of $J/\psi \to B\bar{B}$.

Comments: version accepted by Physics Letters B, revised, discussed added, references added