New signature of low mass Z′ in J/ψ decays* * Supported in part by the National Key Research and Development Program of China under (2020YFC2201501) and the National Natural Science Foundation of China (NSFC) (12347103, 12205063)

We explored a new approach to search for a low-mass particle through decays by identifying its existence through parity-violating phenomena in the isospin-violating final states of and the corresponding charge conjugated states of . Our investigation centered on a generation-independent and leptophobic with mass below 10 GeV. Given the present experimental conditions at Beijing Spectrometer III (BESIII) and the anticipated opportunities at the Super Tau Charm Factory (STCF), we conducted Monte-Carlo simulations to predict possible events at both facilities. Notably, we foresee a substantial enhancement in the precision of the lower limit estimation of as well as a reduction in statistical uncertainty with upcoming STCF experiments. Furthermore, it is essential to highlight that a null result in the measurement of would impose stringent constraints, requiring the couplings to be in the order of .