Baryon-Baryon Interactions : Nijmegen Extended-Soft-Core Models(Chapter I.,Hypernuclei and Baryon-Baryon Interaction)

概要

論文の詳細を見る
We review the Nijmegen extended-soft-core (ESC) models for the baryon-baryon (BB) interactions of the SU (3) flavor-octet of baryons (N, Λ, Σ, and Ξ). The interactions are basically studied from the meson-exchange point of view, in the spirit of the Yukawa-approach to the nuclear force problem [H. Yukawa, "On the interaction of Elementary Particles I", Proceedings of the Physico-Mathematical Society of Japan 17 (1935), 48], using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple-gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. We present in some detail the most recent extended-soft-core model, henceforth referred to as ESC08, which is the most complete, sophisticated, and successful interaction-model. Furthermore, we discuss briefly its predecessor the ESC04-model [Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044007; Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044008; Th. A. Rijken and Y. Yamamoto, nucl-th/0608074]. For the soft-core one-boson-exchange (OBE) models we refer to the literature [Th. A. Rijken, in Proceedings of the International Conference on Few-Body Problems in Nuclear and Particle Physics, Quebec, 1974, ed. R.J. Slobodrian, B. Cuec and R. Ramavataram (Presses Universite Laval, Quebec, 1975), p. 136; Th. A. Rijken, Ph. D. thesis, University of Nijmegen, 1975; M.M. Nagels, Th. A. Rijken and J.J. de Swart, Phys. Rev. D 17 (1978), 768; P.M.M. Maessen, Th. A. Rijken and J.J. de Swart, Phys. Rev. C 40 (1989), 2226; Th. A. Rijken, V.G.J. Stoks and Y. Yamamoto, Phys. Rev. C 59 (1999), 21; V.G.J. Stoks and Th. A. Rijken, Phys. Rev. C 59 (1999), 3009]. All ingredients of these latter models are also part of ESC08, and so a description of ESC08 comprises all models so far in principle. The extended-soft-core (ESC) interactions consist of local- and non-local-potentials due to (i) one-boson-exchanges (OBE), which are the members of nonets of pseudo-scalar-, vector-, scalar-, and axial-mesons, (ii) diffractive (i.e. multiple-gluon) exchanges, (iii) two pseudo-scalar exchange (PS-PS), and (iv) meson-pair-exchange (MPE). The OBE- and pairvertices are regulated by gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the BBM-vertices is dependent on the SU (3)-classification of the exchanged mesons for OBE, and a similar scheme for MPE. The ESC-models ESC04 and ESC08 describe the nucleon-nucleon (NN), hyperon-nucleon (YN), and hyperon-hyperon (YY) interactions in a unified way using broken SU(3)-symmetry. Novel ingredients in the OBE-sector in the ESC-models are the inclusion of (i) the axial-vector meson potentials, (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the meson coupling parameters of the model qualitatively in accordance with the predictions of the ^3P_0 quark-antiquark creation (QPC) model. This is also the case for the F/(F+D)-ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states in ΛN. Broken SU(3)-symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN-interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN ⊕ YN-analysis as input. In ESC04 medium strong flavor-symmetry-breaking (FSB) of the coupling constants was investigated, using the ^3P_0-model with a Gell-Mann-Okubo hypercharge breaking for the BBM-coupling. In ESC08 the couplings are kept SU(3)-symmetric. The charge-symmetry-breaking (CSB) in the Λp and Λn channels, which is an SU(2) isospin breaking, is included in the OBE-, TME-, and MPE-potentials. In ESC04 and ESC08 simultaneous fits to the NN- and the YN- scattering data have been achieved, using different options for the ESC-model. In particularly in ESC08 with single-sets of parameters excellent fits were obtained for the NN- and YN-data. For example, in the case of ESC08a" we have: (i) For the selected 4233 NN-data with energies 0≤T_<lab>≤350MeV, excellent results were obtained having χ^2/N_<data>=1.094. (ii) For the usual set of 35 YN-data and 3 Σ^+p cross-sections from a recent KEK-experiment E289 [H. Kanda et al., AIP Conf. Proc. 842 (2006), 501; H. Kanda, Measurement of the cross sections of Σ^=p elastic scattering, Ph. D. thesis, Department of Physics, Faculty of Science, Kyoto University, March 2007] the fit has χ^2/YN_<data>≈0.83. (iii) For YY there is a weak ΛΛ-interaction, which successfully matches with the Nagara-event [H. Takahashi et al., Phys. Rev. Lett. 87 (2001), 212502]. (iv) The nuclear Σ and Ξ well-dephts satisfy U_Σ>0 and U_Ξ<0. The predictions for the S=-2 (ΛΛ, ΞN, ΛΣ, ΣΣ)-channels are the occurrences of an S=-2 bound states in the ΞN (^3S_1-^3D_1, I=0,1)-channels.
2010-11-30

Baryon-Baryon Interactions : Nijmegen Extended-Soft-Core Models(Chapter I.,Hypernuclei and Baryon-Baryon Interaction)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク