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Elusive exotic states

Hyun-Chul Kim·Mikhail Shmatikov
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Abstract

The existence of flavor exotic $QQ\bar{q}\bar{q}$ molecular-type states is investigated. An attractive force between two {\it pseudoscalar} $H = (Q\bar{q})$ heavy meson is generated by (correlated) two-pion exchange. The emergence of a (loosely) bound state depends crucially on the value of the coupling constant $g$ of the $H^*Hπ$ vertex. For a $g$ value calculated from the experimental upper limit on the width of the $D^*$ meson the considered mechanism alone is strong enough to generate a bound state in the $BB$ system while the $DD$ system is very close to become bound. Such states, if exist, are stable with respect to strong interactions. They may be observed as stable scalar particles with the mass $M\approx 2\,m_H$ and flavor quantum number $\pm 2$.

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Hyun-Chul Kim, Mikhail Shmatikov. 1996-02-21. Elusive exotic states. https://doi.org/10.1016/0370-2693(96)00196-7

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