On leptonic width of X (4260)

New measurements on cross sections in e^+e^-→ J/ψπ ^+π ^- , h_cπ ^+π ^- , D^0D^*-π ^++c.c. , ψ (2S)π ^+π ^- , ωχ _c0 and J/ψη channels have been carried out by BESIII, Belle and BABAR experiments, as well as in the D_s^*+D_s^*- channel. We perform extensive numerical analyses by combining all these data available, together with those in D^+D^*-+c.c. and D^*+D^*- channels. Though the latter show no evident peak around √(s)=4.230 GeV, the missing X (4260) is explained as that it is concealed by the interference effects of the well established charmonia ψ (4040) , ψ (4160) and ψ (4415) . Our analyses reveal that the leptonic decay width of X (4260) ranges from 𝒪(10^2) eV to 𝒪(1) keV, and hence it is probably explained in the conventional quark model picture. That is, the X (4260) may well be interpreted as a mixture of 4^3S_1 and 3^3D_1 ( 2^3D_1 ) states.