Abstract
A review is presented of past and recent attempts to build multiquark states within current models already describing ordinary mesons and baryons. This includes: coherence in the chromomagnetic interaction, tetraquarks with two heavy quarks, Steiner-tree models of confinement, and hadronic molecules, in particular in the hidden-charm sector. Some emphasis is put on the difficulties encountered when extrapolating toward higher configurations the dynamics of confining forces, starting from the simple case of a quark and an antiquark, or three quarks in a colour singlet.
Highlights
In principle, especially in front of this audience of the International Few-Body Conference, the task of describing multiquark spectroscopy should be rather easy: a model is first tuned to fit the spectrum and properties of mesons and baryons, and applied to multiquark configurations
The story started with a nice speculation based of chiral dynamics [17], leading Nakano and his colleagues to attempt a measurement out of the stream of fashion at that time, and to get a positive signal [18]
Especially in the hidden-charm sector, is almost immediately described as a new meson–meson molecule, and the Pandora box syndrome seemingly strikes again. Such a blame cannot be addressed to the X(3872), since it was predicted before its discovery, on the basis of the pion-exchange dynamics
Summary
Especially in front of this audience of the International Few-Body Conference, the task of describing multiquark spectroscopy should be rather easy: a model is first tuned to fit the spectrum and properties of mesons and baryons, and applied to multiquark configurations. The procedure is not that straightforward, because the quark dynamics governing mesons and baryons is not very well known, and, within any assumed model, the extrapolation towards multiquarks involves severe uncertainties. Apologies are presented to the many colleagues whose interesting work is implicitly taken into account, but not explicitly cited
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