Speaker
Prof.
Stephen Lars OLSEN
(University of Chinese Academy of Sciences)
Description
The list of XYZ mesons, which was initiated 16 years ago, continues to expand.
Although these states have a number of common properties, including: large
branching fractions to hidden-quarkonium states (in spite of kinematically
accessible open-flavor, fall-apart decay channels); relatively narrow widths; and
preferences for $J^{P(C)} =1^{+(+)}$ quantum numbers, no single theoretical model can
provide a comprehensive description for them. Since the models that have been
proposed: molecules, tetraquarks, QCD-hybrids, hadro-quarkonium, etc., can, at
best, provide adequate descriptions for only a small subset of the observations, a
concise exposition of what are they? is a Sisyphean task that I have given up on.
Instead, I restrict myself to the easier question: what aren’t they?
Primary author
Prof.
Stephen Lars OLSEN
(University of Chinese Academy of Sciences)
