ESC NN-Potentials in Momentum Space. II. Meson-Pair Exchange Potentials

The partial wave projection of the Nijmegen soft-core potential model for Meson-Pair-Exchange (MPE) for NN-scattering in momentum space is presented. Here, nucleon-nucleon momentum space MPE-potentials are NN-interactions where either one or both nucleons contains a meson-pair vertex. Dynamically, the meson-pair vertices can be viewed as describing in an effective way (part of) the effects of heavy-meson exchange and meson-nucleon resonances. From the point of view of ``duality,'' these two kinds of contribution are roughly equivalent. Part of the MPE-vertices can be found in the chiral-invariant phenomenological Lagrangians that have a basis in spontaneous broken chiral symmetry. It is shown that the MPE-interactions are a very important component of the nuclear force, which indeed enables a very succesful description of the low and medium energy NN-data. Here we present a precise fit to the NN-data with the extended-soft-core (ESC) model containing OBE-, PS-PS-, and MPE-potentials. An excellent description of the NN-data for $T_{Lab} \leq 350$ MeV is presented and discussed. Phase shifts are given and a $\chi^2_{p.d.p.} = 1.15$ is reached.Comment: 27 pages, 5 PostScript figures, revtex

Can the magnetic moment contribution explain the A_y puzzle?

We evaluate the full one-photon-exchange Born amplitude for $Nd$ scattering. We include the contributions due to the magnetic moment of the proton or neutron, and the magnetic moment and quadrupole moment of the deuteron. It is found that the inclusion of the magnetic-moment interaction in the theoretical description of the $Nd$ scattering observables cannot resolve the long-standing $A_y$ puzzle.Comment: 7 pages, 2 Postscript figures; to appear in Phys.Rev.

Hypermatter in chiral field theory

We investigate the properties of hadronic matter and nuclei be means of a generalized $SU(3)\times SU(3)$ $\sigma$ model with broken scale invariance. In mean-field approximation, vector and scalar interactions yield a saturating nuclear equation of state. Finite nuclei can be reasonably described, too. The condensates and the effective baryon masses at finite baryon density and temperature are discussed.Comment: uses IOP style, to be published in Journal of Physics, Proceedings of the International Symposium on Strangeness in Quark Matter 1997, April 14-18, Thera (Santorini), Hella

Yukawa model on a lattice: two body states

We present first results of the solutions of the Yukawa model as a Quantum Field Theory (QFT) solved non perturbatively with the help of lattice calculations. In particular we will focus on the possibility of binding two nucleons in the QFT, compared to the non relativistic result.Comment: 3 pages, talk at "IVth International Conference on Quarks and Nuclear Physics" (Madrid, June 2006

Soft two-meson-exchange nucleon-nucleon potentials. II. One-pair and two-pair diagrams

Two-meson-exchange nucleon-nucleon potentials are derived where either one or both nucleons contains a pair vertex. Physically, the meson-pair vertices are meant to describe in an effective way (part of) the effects of heavy-meson exchange and meson-nucleon resonances. {}From the point of view of ``duality,'' these two kinds of contribution are roughly equivalent. The various possibilities for meson pairs coupling to the nucleon are inspired by the chiral-invariant phenomenological Lagrangians that have appeared in the literature. The coupling constants are fixed using the linear $\sigma$ model. We show that the inclusion of these two-meson exchanges gives a significant improvement over a potential model including only the standard one-boson exchanges.Comment: 21 pages RevTeX, 7 postscript figures; revised version as to appear in Phys. Rev.

Relativistic effects in proton-induced deuteron break-up at intermediate energies with forward emission of a fast proton pair

Recent data on the reaction pD -> (pp) n with a fast forward pp pair with very small excitation energy is analyzed within a covariant approach based on the Bethe-Salpeter formalism. It is demonstrated that the minimum non-relativistic amplitude is completely masked by relativistic effects, such as Lorentz boost and the negative-energy P components in the 1S_0 Bethe-Salpeter amplitude of the pp pair

Strange nuclear matter within Brueckner-Hartree-Fock Theory

We have developed a formalism for microscopic Brueckner-type calculations of dense nuclear matter that includes all types of baryon-baryon interactions and allows to treat any asymmetry on the fractions of the different species (n, p, $\Lambda$, $\Sigma^0$, $\Sigma^+$, $\Sigma^-$, $\Xi^-$ and $\Xi^0$). We present results for the different single-particle potentials focussing on situations that can be relevant in future microscopic studies of beta-stable neutron star matter with strangeness. We find the both the hyperon-nucleon and hyperon-hyperon interactions play a non-negligible role in determining the chemical potentials of the different species.Comment: 36 pages, LateX, includes 8 PostScript figures, (submitted to PRC

Effective range expansion in various scenarios of EFT(\notpi)

Using rigorous solutions, we compare the ERE parameters obtained in three different scenarios of EFT(\notpi) in nonperturbative regime. A scenario with unconventional power counting (like KSW) is shown to be disfavored by the PSA data, while the one with elaborate prescription of renormalization but keeping conventional power counting intact seems more promising.Comment: 6 pages, 3 tables, no figure, revtex4-1, minor revisions, to appear in EP

On the Surface Structure of Strange Superheavy Nuclei

Bound, strange, neutral superheavy nuclei, stable against strong decay, may exist. A model effective field theory calculation of the surface energy and density of such systems is carried out assuming vector meson couplings to conserved currents and scalar couplings fit to data where it exists. The non-linear relativistic mean field equations are solved assuming local baryon sources. The approach is calibrated through a successful calculation of the known nuclear surface tension.Comment: 12 pages, 9 figure