Analysis of Y(2175) as a tetraquark state with QCD sum rules
  In this article, we take the point of view that Y(2175) be a tetraquark state which consists of color octet constituents, and calculate its mass and decay constant within the framework of the QCD sum rule approach. We release standard criterion in the QCD sum rules approach and take more phenomenological analysis, the value of the mass of Y(2175) is consistent with experimental data; there may be some tetraquark components in the state Y(2175). If we retain standard criterion, larger mass than experimental data can be obtained, the current $J_\mu(x)$ can interpolate a tetraquark state with larger mass, or Y(2175) has some components with larger mass. The dominating contribution comes from the perturbative term, which is in contrast to the sum rules with interpolating currents constructed from diquark pairs. The tetraquark states may consist of color octet constituents rather than diquark pairs. 
Zhi-Gang Wang (NCEPU, Baoding)