Isospin violating decays of vector charmonia

We study the isospin violating decays of vector charmonia to $\mathrm{\Lambda }{\bar{\mathrm{\Sigma }}}^0$ and its charge conjugate. They are dominated by the single photon annihilation and can be evaluated reliably with timelike form factors. We utilize the quark-pair creation model, which is valid for the OZI suppressed decays, to evaluate the form factors. We obtain the branching fractions of $\mathcal{B}(J\mathrm{/}\psi \to \mathrm{\Lambda }{\bar{\mathrm{\Sigma }}}^0+c\mathrm{.}c\mathrm{.})=(2.4\pm 0.4)\times {10}^{-5}$ and $\mathcal{B}(\psi (2S)\to \mathrm{\Lambda }{\bar{\mathrm{\Sigma }}}^0+c\mathrm{.}c\mathrm{.})=(3.0\pm 0.5)\times {10}^{-6}$, which are compatible with the measurements by the BESIII collaborations, respectively. The decay asymmetries are found to be ${\alpha }_{J\mathrm{/}\psi }=0.314$ and ${\alpha }_{\psi (2S)}=0.461$, which can be examined at BESIII in the foreseeable future.