Analysis ofNNamplitudes up to 2.5 GeV: An optical model and geometric interpretation

Abstract

We analyse the SM97 partial wave amplitudes for nucleon-nucleon (NN) scattering to 2.5 GeV, in which resonance and meson production effects are evident for energies above pion production threshold. Our analyses are based upon boson exchange or quantum inversion potentials with which the subthreshold data are fit perfectly. Above 300 MeV they are extrapolations, to which complex short ranged Gaussian potentials are added in the spirit of the optical models of nuclear physics and of diffraction models of high energy physics. The data to 2.5 GeV are all well fit. The energy dependences of these Gaussians are very smooth save for precise effects caused by the known ∆ and N ⋆ resonances. With this approach, we confirm that the geometrical implications of the profile function found from diffraction scattering are pertinent in the regime 300 MeV to 2.5 GeV and that the overwhelming part of meson production comes from the QCD sector of the nucleons when they have a separation of their centres of 1 to 1.2 fm. This analysis shows that the elastic NN scattering data above 300 MeV can be understood with a local potential operator as well as has the data below 300 MeV.

Nucleon-nucleon optical model for energies up to 3 GeV

“…Such is a condition for the suitability of a potential model of scattering governed by quasi macroscopic geometric entities. used previously [16] a local Gaussian in this same manner, noticing therefrom spin-isospin coupling effects more substantial than found with NA scattering. It is also worth noting that the absorption in those NN optical potentials for this energy range were not at the geometric limit of a fully absorptive disc.…”

“…If a very large number of doorway states contribute, the effect equates to a local potential operator. This was the basis of our previous study [16].…”

“…All such have given but qualitative results, often requiring many degrees of freedom even to achieve that qualitative agreement and despite explicit inclusion of ∆ and N * resonances. Optical model studies have also been made for medium and modest high energy NN scattering [15,16,17], and they can be improved to give a high quality description of scattering at medium energy.…”

Modelling nucleon-nucleon scattering above 1 GeV

“…In configuration space (r-space) calculations, the following form has been used for a nonrelativistic optical potential [58]:…”

9. The nucleon-nucleon interaction

“…The latter data were never explained in a really satisfatory way in spite of some efforts [152,153]. During the past decade, theory has shown little interest in NN scattering at energies of 1-10 GeV and only a few papers can be cited [154,155,156,157,158,159]. The reason for the neglect is probably that these energies are too high for traditional nuclear physicists and too low for high energy physicists; so, this range is the stepchild of both professions.…”