Coupled-channel study of crypto-exotic baryons with charm

By J. Hofmann, M. Lutz. 2005

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Abstract Identifying a zero-range exchange of vector mesons as the driving force for the s-wave scattering of pseudo-scalar mesons off the baryon ground states, a rich spectrum of molecules is formed. We argue that chiral symmetry and large- N c considerations determine that part of the interaction which generates the spectrum. A bound state with exotic quantum numbers is predicted at mass 2.78 GeV. It couples strongly to the ( D ¯ s N ) , ( D ¯ Λ ) , ( D ¯ Σ ) channels. A further charm minus-one system is predicted at mass 2.84 GeV as a result of ( D ¯ s Λ ) , ( D ¯ Ξ ) interactions. We suggest the existence of strongly bound crypto-exotic baryons, which contain a charm–anti-charm pair. Such states are narrow since they can decay only via OZI-violating processes. A narrow nucleon resonance is found at mass 3.52 GeV. It is a coupled-channel bound state of the ( η c N ) , ( D ¯ Σ c ) system, which decays dominantly into the ( η ′ N ) channel. Furthermore two isospin singlet hyperon states at mass 3.23 and 3.58 GeV are observed as a consequence of coupled-channel interactions of the ( D ¯ s Λ c ) , ( D ¯ Ξ c ) and ( η c Λ ) , ( D ¯ Ξ c ′ ) states. Most striking is the small width of about 1 MeV of the lower state. The upper state may be significantly broader due to a strong coupling to the ( η ′ Λ ) state. The spectrum of crypto-exotic charm-zero states is completed with an isospin triplet state at 3.93 GeV and an isospin doublet state at 3.80 GeV. The dominant decay modes involve again the η ′ meson. The two so far observed s-wave baryons with charm one are recovered. We argue that the Λ c ( 2880 ) is not a s-wave state. In addition to those states we predict the existence of about ten narrow s-wave baryon states with masses below 3 GeV. A triplet of crypto-exotic states decaying dominantly into channels with an η ′ is obtained with masses 4.24 and 4.44 GeV. In the charm-two sector we predict in addition to the chiral excitations of the ground states two triplets of bound states formed by channels involving open-charm mesons. The binding energy of the latter is larger than the one of the chiral excitations.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a2a6a78c284894a7d0cc56cb1a01e50beda85a64

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