We discuss the possibility that the two nearby resonances observed by BESIII partially below the pp threshold might be due to mixing between two metastable states with the same J^PC=0^-+ quantum numbers, but rather different internal structure. One is a pp hadronic molecule and the other a bound state of a light-quark diquark and an antidiquark, both with spin 1 and isospin 0, a composite color antitriplet and triplet, respectively. The doubling of resonances, one of which may be interpreted as a hadronic molecule, while the other arises from qq annihilation in a state with vacuum quantum numbers, may be a more general feature than the specific case considered here.
Karliner et al. (Wed,) studied this question.