FIG. 1: The distribution of the measured charge q$_{d}$ for ψ (2 S ) → ddJ/ψ, J/ψ → e $^{+}$e − with the input m$_{d}$ = 0 . 005 GeV. The shaded area is the signal events. The others are background events. The statistics is only for the signal events. FIG. 2: The scatter of the measured m 2 d versus the charge q$_{d}$ for ψ (2 S ) → ddJ/ψ, J/ψ → e $^{+}$e − with the input m$_{d}$ = 0 . 005 GeV. The squares are the signal events. The others are background events. The statistics is only for the signal events.  q 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Events/0.01 0 2 4 6 8 10 Entries   36 Mean 0.3386 RMS 0.01486  22 0.5237 0.1894 2  mass -0.1 -0.05 0 0.05 0.1 0.15 0.2 q 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Entries   44 Mean x  0.01883 Mean y  0.5387 RMS x  0.0283 RMS y  0.1773  72 0.0001078 0.3386 0.005597 0.01486 8 [2] Mod. Phys. Lett. A19 (2004) 2595, M. L. Perl, et al . [3] Z. Phys. C6 (1980) 295, W. Bartel, et al . Phys. Rev. Lett 52 (1984) 2332, H. Aihara, et al . Phys. Lett. B139 (1984) 313, W. Guryn, et al . Phys. Lett. B156 (1985) 134, H. Albrecht, et al .