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تسجيل مستخدم جديدComparative study of hyperon-nucleon interactions of quark model and chiral effective field theory by low-momentum equivalent interactions and $G$ matrices
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M. Kohno
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Hyperon-nucleons interactions constructed by two frameworks, the Kyoto-Niigata SU$_6$ quark model and the chiral effective field theory, are compared by investigating equivalent interactions in a low-momentum space and in addition by calculating hyperon single-particle potentials in the lowest-order Brueckner theory in symmetric nuclear matter. Two descriptions are shown to give similar matrix elements in most channels after renormalizing high momentum components. Although the range of the $Lambda N$ interaction is different in two potentials, the $Lambda$ single-particle potential in nuclear matter is very similar. The $Sigma$-nucleus and $Xi$-nucleus potentials are also found to be similar. These predictions are to be confronted with forthcoming experimental data.
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Equivalent interactions in a low-momentum space for the $Lambda N$, $Sigma N$ and $Xi N$ interactions are calculated, using the SU$_6$ quark model potential as well as the Nijmegen OBEP model as the input bare interaction. Because the two-body scatte
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rder term is incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the nucleon and Lambda, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region q_1=5 - 20 fm^-1. A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the rho-meson exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up to T_lab=350 MeV are greatly improved especially for the 3E states. The low-energy observables of the nucleon-nucleon and the hyperon-nucleon interactions are also reexamined. The isospin symmetry breaking and the Coulomb effect are properly incorporated in the particle basis. The essential feature of the Lambda N - Sigma N coupling is qualitatively similar to that obtained from the previous models. The nuclear saturation properties and the single-particle potentials of the nucleon, Lambda and Sigma are reexamined through the G-matrix calculation. The single-particle potential of the Sigma hyperon is weakly repulsive in symmetric nuclear matter. The single-particle spin-orbit strength for the Lambda particle is very small, in comparison with that of the nucleons, due to the strong antisymmetric spin-orbit force generated from the Fermi-Breit interaction.
The $Lambda N$ and $Sigma N$ interactions are considered at next-to-leading order in SU(3) chiral effective field theory. Different options for the low-energy constants that determine the strength of the contact interactions are explored. Two variant
s are analysed in detail which yield equivalent results for $Lambda N$ and $Sigma N$ scattering observables but differ in the strength of the $Lambda N to Sigma N$ transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the $Lambda$ and $Sigma$ hyperons in nuclear matter is investigated and discussed. The effect of the variation in the potential strength of the $Lambda N$-$Sigma N$ coupling (also called $Lambda -Sigma$ conversion) is found to be moderate for the considered $^3_Lambda rm H$ and $^4_Lambda rm He$ hypernuclei but sizable in case of the matter properties. Further, the size of three-body forces and their relation to different approaches to hypernuclear interactions is discussed.
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Motivated by the recent experimental measurements of differential cross sections of the $Sigma^{-}p$ elastic scattering in the momentum range of $470$ to $850$ MeV$/c$ by the J-PARC E$40$ experiment, we extend our previous studies of $S=-1$ hyperon-n
ucleon interactions to relatively higher energies up to $900$ MeV$/c$ for both the coupled-channel $Lambda prightarrow(Lambda p, Sigma^{+}n, Sigma^{0}p)$, $Sigma^{-}prightarrow(Lambda n, Sigma^{0}n, Sigma^{-}p)$ and single-channel $Sigma^{+}prightarrowSigma^{+}p$ reactions. We show that although the leading order covariant chiral effective field theory is only constrained by the low energy data, it can describe the high energy data very well, in particular, the J-PARC E40 differential cross sections. In particular, we predict a pronounced cusp structure close to the $Sigma N$ threshold in the $Lambda pto Lambda p$ reaction, which can be checked in the future using, e.g., the Femtoscopy technique. The predicted total and differential cross sections are of relevance for ongoing and planned experiments.
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