The Δ-statistics of uncoventional quarkonium-like resonances

In this Letter we address the problem of unconventional charmonium-like levels from the standpoint of level spacing theory. The level distribution of the newly discovered vector resonances is compared to that of standard charmonia analyzing their spectral rigidities. It is found that the unconventional charmonium-like states are significantly more compatible with the hypothesis of being levels from a Gaussian Orthogonal Ensamble of Random Matrices than the standard ones, which in turn seem more likely to be Poisson distributed. We discuss the consequences of this result and draw some hints for future investigations.