Triton calculations with the new Nijmegen potentials

Abstract

Triton properties are calculated using new nucleon-nucleon potentials, which were fit to the world nucleon-nucleon data. All potentials are charge dependent and explicitly incorporate the mass difference between the charged and neutral pions. Three of these models have a nearly optimal χ 2 per degree of freedom and can therefore be considered as alternative partial-wave analyses, which in quality can almost compete with the Nijmegen partial-wave analysis. The triton binding energy obtained with three local models (Nijm II, Reid93, AV18) can be summarized as 7.62±0.01 MeV, which is nearly 900 keV lower than experiment. The non-local model Nijm I binds by 7.72 MeV.Typeset using REVT E X 1

Energy Dependence of the πN Amplitude and the Three-Nucleon Interaction

“…48 MeV, has been an outstanding problem in nuclear physics for a number of years [1]. A commonly accepted solution has been the introduction of a three-nucleon force that will bridge the gap between the calculated binding energy [2][3][4][5], based on a two-body interaction, and the experimental binding energy. The origin of such a three-body force is partly the result of the fact that the nucleons are treated as point particles interacting via a two-body meson exchange potential that is often assumed to be local.…”

Assessment of Triton Potential Energy

“…This suppression will also tend to reduce the overall effect of relativity at small separations. The latter is known to produce contributions of ∼ 100 keV additional triton attraction in some nuclear force models [2]. In any event, the short-range structures in the potential produce relatively little net effect, as we shall show.…”

“…Replacing the latter potential with a "pure" OPEP potential leads to nearly the same triton binding energy, demonstrating that OPEP dominates triton binding. This was more clearly documented [2,4] by subsequent calculations of V π for the triton, alpha particle and other systems: the fraction of the potential energy from OPEP, V π / V , is 70-80% for most realistic potentials. Not surprisingly, OPEP has an even more dominant effect in the deuteron, where an adequate (but not excellent) deuteron can be obtained using a pure regulated OPEP; ironically, OPEP is too strong at short distances to make a good deuteron without the regulation [3].…”

“…One recent calculation [2] underscores the recent and potential precision of the field. The Nijmegen group have constructed several new potential models, whose dominant feature is a charge-dependent one-pion-exchange potential (OPEP) [see below], by directly fitting the model parameters to the nucleon-nucleon (NN) scattering data.…”

“…For very large x, this quantity approaches 100%. Figure 1 shows the results for the original version of the Argonne V 18 potential [2] (although other models that were examined are virtually identical) for the kinetic energy (Ô = T ), the potential energy (Ô = V ), and the correlation function (Ô = 1). The effect of the strong short-range repulsion is the dominant feature inside an interparticle separation of 1 fm.…”