Perspective study of exotics above the D(D)over-bar threshold

The spectroscopy of exotic states with hidden charm is discussed. Together with charmonium, these provide a good tool for testing theories of the strong interactions including both perturbative and non-perturbative QCD, lattice QCD, potential and other phenomenological models. An elaborated analysis of exotics spectrum is given, and attempts to interpret recent experimentally observed states with masses above the D (D) over bar threshold region are considered. Experimental results from different collaborations (BES, BaBar, Belle, LHCb) are analyzed with special attention given to recently discovered hidden charm states. Some of these states can be interpreted as higher-lying charmonium states and others as tetraquarks with hidden charm. It has been shown that charged/neutral tetraquarks must have their neutral/charge partners with mass values differing by at most a few MeV c(-2), hypotheses that tend to coincide with those proposed by Maiani and Polosa. However, measurements of different decay modes are needed before firm conclusions can be made. These data can be derived directly from experiments using a high quality antiproton beam with momentum up to 15 GeV c(-1) and proton-proton collisions with momentum up to 26 GeV c(-1). © 2015 The Royal Swedish Academy of Sciences Printed in the UK11sciescopu