Abstract
Abstract. 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 DD 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 differ 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 the experiments using ahigh quality antiproton beam with momentum up to 15 GeV/c and proton-proton collisions with momentum up to 26 GeV/c. DD
Highlights
The study of strong interactions and hadron matter in the process of antiproton-proton annihilation and proton-proton collisions seems to be a challenge nowadays
The values of the calculated widths coincide with the experimentally determined values for the XYZ particles; the correspondence of the mass values has been discussed above. This fact strongly suggests that some of the XYZ particles may be interpreted as higher-lying charmonium states [9, 10] and tetraquarks as it can be verified by the experiments with antiproton beams with momentum up to 15 GeV/c and proton-proton collisions with momentum up to 26 GeV/c
The prospects for future exotics research are related with the results obtained below: A combined approach has been employed to study charmonium and exotics on the basis of the quarkonium potential model and a confinement model that uses a three-dimensional sphere embedded into the four-dimensional Euclidian space of the decay products
Summary
The study of strong interactions and hadron matter in the process of antiproton-proton annihilation and proton-proton collisions seems to be a challenge nowadays. Studies of the spectra of charmed hybrids ссg and tetraquarks containing hidden charm ( сqсqc , q and qc = u, d, s),together with completion of the charmonium spectrum are promising approaches for the development of an understanding of the dynamics of quark interactions at small distances. They provide a good testing tool that challenges theories of strong interactions: QCD in both perturbative and non-perturbative regimes, QCD inspired potential models, phenomenological models, and nonrelativistic QCD and LQCD. Discussions have been focused only around the lowest-lying charmonium hybrids Four of these states JPC = 2-+, 1-+, 1- -, 0-+ correspond to a сс pair with JPC = 0-+ or 1--, coupled to a gluon in the lightest mode with JPC = 1+-. A prediction that distinguishes tetraquarks containing a сс pair from conventional charmonia is possible existence of multiplets that include members with non-zero charge сuсd , strangeness cdcs , or both cucs
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