Soft-core baryon-baryon one-boson-exchange models. II. Hyperon-nucleon potential.

Abstract

The results of the Nijmegen soft-core potential model are presented for the low-energy YN interactions. The YN version of the model is obtained by a straightforward extension of the NN model through the application of SU(3). The potentials are due to the dominant parts of the \ensuremath{\pi}, \ensuremath{\eta}, \ensuremath{\eta}', \ensuremath{\rho}, \ensuremath{\omega}, \ensuremath{\varphi}, \ensuremath{\delta}, \ensuremath{\varepsilon}, and ${S}^{\mathrm{*}}$ Regge trajectories. This gives the traditional one-boson-exchange potentials. In addition to these, the J=0 contributions from the tensor f,f',${A}_{2}$ and Pomeron trajectories are included in the potentials. The latter give potentials of the Gaussian type. Also the form factors from Regge poles are Gaussian, which guarantees that the potentials have a soft behavior near the origin. The multichannel Schr\odinger equation is solved in configuration space for the (partially) nonlocal potentials. We work on the particle basis and include the Coulomb interaction exactly.The meson-baryon coupling constants are calculated via SU(3), using the coupling constants of the NN analysis as input. Charge symmetry breaking in the \ensuremath{\Lambda}p and \ensuremath{\Lambda}n channels is included. An excellent description is achieved of the available low-energy data per degree of freedom (${\ensuremath{\chi}}^{2}$\ensuremath{\approxeq}0.58 for 35 YN data). In particular, we were able to fit the inelastic capture ratio at rest perfectly. We have ${r}_{R}$=0.471, where experimentally the average value is ${r}_{R}$=0.468\ifmmode\pm\else\textpm\fi{}0.010. The obtained values for the adjustable mixing angles and F/(F+D) ratios agree very well with the literature. We find ${\ensuremath{\alpha}}_{\mathrm{PV}=0.355}$ and ${\ensuremath{\alpha}}_{V}^{m}$=0.275. For the scalar-meson mixing angle we obtain ${\ensuremath{\theta}}_{s}$=40.895\ifmmode^\circ\else\textdegree\fi{}, which lies between the ideal mixing angles for the scalar ${q}^{2}$q\ifmmode\bar\else\textasciimacron\fi{} $^{2}$ and qq\ifmmode\bar\else\textasciimacron\fi{} states. In the \ensuremath{\Lambda}p system we find a cusp at the ${\ensuremath{\Sigma}}^{+}$n threshold, but there is on the second Riemann sheet no pole in the vicinity causing this cusp. The predictions of the total cross sections up to the pion production threshold are given and compared to the experimental data.