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arXiv · 2001.05884

Triangle Singularities and Charmonium-like $XYZ$ States

Feng-Kun Guo
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Abstract

The spectrum of hadrons is important for understanding the confinement of quantum chromodynamics. Many new puzzles arose since 2003 due to the abundance of experimental discoveries with the $XYZ$ structures in the heavy quarkonium mass region being the outstanding examples. Hadronic resonances correspond to poles of the $S$-matrix, which has other types of singularities such as the triangle singularity due to the simultaneous on-shellness of three intermediate particles. Here we briefly discuss a few possible manifestations of triangle singularities in the $XYZ$ physics, paying particular attention to the formalism that can be used to analyze the data for charged $Z_c$ structures in the $ψπ$ distributions of the reaction $e^+e^-\to ψπ^+π^-$.

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Feng-Kun Guo. 2021-03-01. Triangle Singularities and Charmonium-like $XYZ$ States. https://doi.org/10.11804/nuclphysrev.37.2019cnpc52

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