Two-Pion Exchange Nuclear Potential — Chiral Cancellations

Abstract

We show that chiral symmetry is responsible for large cancellations in the two-pion exchange nucleon-nucleon interaction, which are similar to those occuring in free pion-nucleon scattering.

Two-pion exchange nucleon-nucleon potential model independent features

“…Nowadays, the evaluation of this part of the potential in the framework of chiral symmetry has no important ambiguities and is quite well understood. This minimal T P EP fulfills the expectations from chiral symmetry and, in particular, reproduces at the nuclear level the well known cancellations of the intermediate πN amplitude [10,11]. On the other hand, it fails to yield the qualitative features of the medium range scalarisoscalar NN attraction [8,12].…”

Nucleon-nucleon interaction and isospin violation

“…The fair agreement of this first calculation and data up to laboratory energies of 100 MeV or so suggests that this may become an alternative to other, more model-dependent approaches to the two-nucleon problem. Further examination of aspects of two-pion exchange in this context can be found in Celenza et al (1992), Friar and Coon (1994), da Rocha and Robilotta (1994), da Rocha and Robilotta (1995), da Rocha and Robilotta (1997), Ballot et al (1997), Savage (1997), and Kaiser et al (1997).…”

NNscattering: Chiral predictions for asymptotic observables

“…As far as dynamics is concerned, we have shown that chiral symmetry is responsible for large cancellations in the pure nucleon sector (Fig. 1, A) [16,17] and eventually the contributions from this sector turn out to be much smaller than those arising from other degrees of freedom. The main contribution to the intermediate attraction is due to processes containing nucleons in one leg and the remainder degrees of freedom in the other.…”

“…1 (A) [6][7][8][9][10]12]. These processes constitute an autonomous chiral family, incorporate correctly the well known cancellations of the intermediate πN amplitude [16,17] but correspond to an intermediate amplitude which is too simple for reproducing πN experimental data [18].…”