A POSSIBLE SOLUTION TO THE E/ι PUZZLE

Apparent experimental conflict in the 1.4 GeV mass region for non-strange mesons can be resolved if there are three states: the 1.45 GeV ι, which is mainly gluonium; a 1.42 GeV 0− predominantly [Formula: see text] state, probably the missing η′ in the radially excited nonet; and a 1.42 GeV 1+ mainly light-quark state, which does not fit in the 1++ nonet. The third of these appears to be a possible candidate for a four-quark meson.