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Two-Photon Production of Four-Quark States Up to the $J/ψ$ Energy

N. N. Achasov·G. N. Shestakov
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Abstract

Evidence for an explicitly exotic state with isospin 2 and spin-parity 2^+ near the $ρρ$ threshold and nontrivial complementary indications of the unusual quark composition of the $f_0(980)$ and $a_0(980)$ states obtained from the reactions of two-photon formation of neutral meson resonances are discussed, together with puzzling phenomena in the channels $γγ\toρ^0ϕ$ and $γγ\toρ^0ρ^0$ at high energies.

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N. N. Achasov, G. N. Shestakov. 1999-04-07. Two-Photon Production of Four-Quark States Up to the $J/ψ$ Energy. https://arxiv.org/abs/hep-ph/9904254

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