The branching fraction measurements of $J\mathrm{/}\psi$ decay into $\rho \eta$ and $\phi \eta$ final states

We present measurements of the branching fractions for the $J\mathrm{/}\psi$ meson decays into the $\rho \eta$ and $\phi \eta$ final states, based on data collected with the KEDR detector at the VEPP-4M collider. The data set consisted of 4.93 million $J\mathrm{/}\psi$ events. The resulting branching fractions are: - $\mathcal{B}(J\mathrm{/}\psi \to \rho \eta )=(2.04\pm 0.58\pm 0.39)\times {10}^{-4}$, - $\mathcal{B}(J\mathrm{/}\psi \to \phi \eta )=(7.82\pm 1.17\pm 0.58)\times {10}^{-4}$, where the first uncertainty is statistical and the second one is systematic. In the study of the $\rho \eta$ decay, the dynamics of $J\mathrm{/}\psi \to {\pi }^{+}{\pi }^{-}\eta$ is analyzed. The hints from contributions of $\rho (1450)\eta$ and $a_2^{\pm }{\pi }^{\mp }$ intermediate states are observed. Additional measured branching fractions in the model that includes $\rho (1450)\eta$ and $a_2^{\pm }{\pi }^{\mp }$ are: - $\mathcal{B}(J\mathrm{/}\psi \to {\pi }^{+}{\pi }^{-}\eta )=(4.73\pm 0.49\pm 1.17)\times {10}^{-4}$, - $\mathcal{B}(J\mathrm{/}\psi \to (a_2^{+}{\pi }^{-}+a_2^{-}{\pi }^{+}))=(1.05\pm 0.37\pm 0.34)\times {10}^{-3}$, - $\mathcal{B}(J\mathrm{/}\psi \to \rho (1450)\eta \to {\pi }^{+}{\pi }^{-}\eta )<1.51\times {10}^{-4}$, at a confidence level of 90%. All results are consistent with previous studies.