Lowest vector tetraquark states. Y(4260/4220) or Z_c(4100)

In this article, we take the Y(4260/4220) as the vector tetraquark state with J^PC = 1^--, and construct the Cγ₅ × ↔∂_μ × γ₅C type diquark-antidiquark current to study its mass and pole residue with the QCD sum rules in details by taking into account the vacuum condensates up to dimension 10 in a consistent way. The predicted mass M_Y = 4.24 ± 0.10 GeV is in excellent agreement with experimental data and supports assigning the Y(4260/4220) to be the Cγ₅ × ↔∂_μ × γ₅C type vector tetraquark state, and disfavors assigning the Z_c(4100) to be the Cγ₅ × ↔∂_μ × γ₅C type vector tetraquark state. It is the first time that the QCD sum rules have reproduced the mass of the Y(4260/4220) as a vector tetraquark state. (orig.)