NNscattering: Chiral predictions for asymptotic observables

Abstract

We assume that the nuclear potential for distances larger than 2.5 fm is given just by the exchanges of one and two pions and, for the latter, we adopt a model based on chiral symmetry and subthreshold pion-nucleon amplitudes, which contains no free parameters. The predictions produced by this model for nucleon-nucleon observables are calculated and shown to agree well with both experiment and those due to phenomenological potentials. ͓S0556-2813͑98͒01503-9͔

Peripheral NN-scattering: role of delta-excitation, correlated two-pion and vector meson exchange

“…(25,26,27) can be easily understood from relations between the tensor operator S 12 (r) = 3 σ ·r σ 2 ·r − σ 1 · σ 2 and the spin-spin operator σ 1 · σ 2 . These relations are: Note that the relevant energy difference ∆/12 = 24.4 MeV in eq.…”

“…In the other cases it can be read off from eqs. (25,26,27). We note that throughout the large-r asymptotics is determined alone by the box graphs with single ∆-excitation b).…”

“…Similar results were found recently in ref. [25] using a somewhat different approach to the 2π-exchange. Compared to our previous calculation [1], there is no improvement in the D-wave phase shifts and ǫ 2 due to adding (perturbative) ρ-and ω-exchange.…”

“…(25,26,27)) are exact for the isoscalar central and the isovector spin-spin/tensor potentials generated by the direct and crossed box graph with single ∆-excitation (in the static limit M → ∞). Heuristic considerations already suggest such a form of the isoscalar central 2π-exchange potential.…”

σfields and chiral scalars in nuclear three-body potentials

“…However, a Lagrangian containing only pions and nucleons cannot reproduce low-energy πN data and hence this very reliable part of the model has to be complemented [5,6]. The combination of chiral symmetry and experimental information about the intermediate πN amplitude, based on dispersion relations, was brought into this problem in the last two years [6], with a successful description of asymptotic NN scattering data [7,8].…”