Hard core attraction in hadron scattering and the family of the Ds meson molecule

We study the discovered Ds(2317) at BABAR, CLEO and BELLE, and find that it belongs to a class of strange multiquarks, which is equivalent to the class of kaonic molecules bound by hard core attraction. In this class of hadrons a kaon is trapped by a s-wave meson or baryon. To describe this class of multiquarks we apply the Resonating Group Method, and extract the hard core kaon-meson(baryon)interactions. We derive a criterion to classify the attractive channels. We find that the mesons f0(980), Ds(2457), Bs scalar and axial, and also the baryons with the quantum numbers of Λ,Ξc,Ξb and also Ωcc,Ωcb and Ωbb belong to the new hadronic class of the Ds(2317). Recently new narrow scalar resonances Ds(2317) and Ds(2457) were discovered at BABAR [1], CLEO [2] and BELLE [3]. These positive parity resonances [4] were also predicted by Nowak, Ro and Zahed [5, 6] as chiral partners of the well known negative parity Ds(1968) and Ds(2112). Here we find that the new Ds resonances can be undesrtood as tetraquarks, or equivalently as D-K molecules [7] bound by the hardcore attraction. These are not standard hadrons because they are neither quarkantiquark mesons nor three quark baryons. The experimental discovery of these hadrons also prompts us to study the new hadronic class which includes the Ds(2317). In our framework the masses and couplings of hadrons are microscopically computed at the quark level and in a chiral invariant framework, [8, 9, 10]. In this talk we study the family of all possible narrow tetraquark and pentaquark resonances [11] where the quark s, or the Kaon play a crucial role. We start by reviewing the Resonating Group Method (RGM) [12]. The RGM, together with chiral symmetry, produces hard core hadron-hadron potentials, which can be either repulsive or attractive. We derive a criterion to discriminate which systems bind and which are unbound. We apply this criterion to find, among the s-wave hadrons, the candidates to trap a kaon. Finally we compute the binding energy of the selected hadrons, the positive parity mesons f0(980),D (0+) s , D (1+) s , B (0+) s , B (1+) s and the negative parity baryons Λ(1405),Ξ (−) c ,Ξ (−) b and also Ω(−) cc ,Ω (−) cb and Ω (−) bb . The RGM computes the effective multiquark energy using the matrix elements of the microscopic quark-quark interactions. The multiquark state is decomposed in antisymmetrized combinations of simpler colour singlets, the baryons and mesons. The RGM was first used in hadronic physics by Ribeiro [13] to show that in exotic hadronhadron scattering, the quark-quark potential together with the Pauli repulsion of quarks produces a repulsive short range interaction. For instance this explains the N −N hard core repulsion, preventing nuclear collapse. Deus and Ribeiro [14] used the same RGM