Baryon–Baryon Interactions S = 0, −1, −2, −3, −4

Abstract

We review the extended-soft-core models ESC08, which at present are the most complete meson-exchange models for the baryon–baryon (BB) interactions. The ESC-model describes the nucleon–nucleon (NN), hyperon–nucleon (YN), and hyperon–hyperon (YY), in terms of meson-exchanges using (broken) SU(3,F)-symmetry. In this approach to baryon-baryon the dynamics is derived from (1) one-boson-exchanges (OBE), (2) two-meson-exchanges, and (3) meson-pair-exchanges, (4) multiple gluon-exchanges (MGE), and (5) quark-core effects. In the OBE-sector, special features are (a) the axial-vector meson potentials, and (b) the inclusion of a zero in the scalar- and axial- meson form-factors. Novel for the ESC08-versions is (a) the inclusion in MGE next to the pomeron the odderon-exchange, and (b) the analysis of possible (pronounced) effects of the appearance of forbidden six-quark configurations. With these ingredients a rather flexible dynamical model is constructed for the description of all BB-channels in the {8} × {8} SU(3,F)-representation. Namely, it appeared feasible to keep the meson coupling parameters of the model in accordance with the predictions of the quark-pair-creation model, with a clear dominance of the 3P0-mechanism. This is the case for the meson- and meson-pair-baryon coupling constants and the F/(F + D)-ratio’s as well. The NN, YN, and YY results for this model are excellent. This is marked in particular by the NN-results, namely \({\chi^2_{p.d.p.}}\) = 1.180, 1.135, and 1.085 for, respectively, ESC08a, ESC08b, and ESC08c. These fits were achieved with partial-wave independent meson-coupling parameters in a combined fit of the \({NN \oplus YN}\) -data, supplemented with information from G-matrix calculations of hypernuclei, e.g. \({B_\Lambda(^{6}_{\Lambda\Lambda}He)}\) from the Nagara-event, and an attractive Ξ-nucleus interaction. The special quark-core effects provide ample repulsion in the Σ+p(3S1, T = 3/2)- and ΣN(1S0, T = 1/2)-channels, in particular for ESC08a,b. The well depths (UΛ, UΣ, UΞ) correspond rather well with expectations from hypernuclei. Here, in ESC08c a universal repulsion, which we derived from multiple pomeron-exchange, is necessary. This at the same time gives both a very satisfactory nuclear saturation point as well as a description of the neutron star matter in the presence of hyperons for all ESC08-models. The requirement of a sizable Ξ-nucleus attraction leads to the prediction of an S = −2 deuteron-state in ΞN(3S1, T = 1) with EB ≈ 8.3 MeV. Also possible/likely are similar bound states for Ξ N(3S1, T = 0), Λ Ξ, Σ Ξ(3S1, T = 1/2, 3/2), and Ξ Ξ(1S0, T = 1).