One-Boson-Exchange Model of Nucleon-Nucleon Scattering for the 0 - 3 GeV Energy Range

Abstract

With the technique of dispersion relation one-boson-exchange models involving rc, p, w, 'tJv, f and cr(O+, 1=0, 416 MeV) are studied for the nucleon-nucleon interaction below 3 GeV. The models give qualitatively good fits to all observables of proton-proton scattering at 670, 970 and 1400 MeV, in addition to nucleon-nucleon elastic data. Effects of absorption on phase shifts, nucleon~meson form factor and high-energy cutoff of the one-boson-exchange ampli­ tudes are discussed. Nucleon-nucleon scattering amplitudes in which a meson with an arbi­ trary spin is exchanged' are formulated. 3 > was found to be successful in describing the nucleon-nucleon interaction at· an internucleon distance larger than 0.5p,.. -I, it was difficult to explain the S wave phase shifts which re­ present sensitively the interaction at a smaller distance. In our recent works, however, we have introduced a nucleon-meson form factor to the OBEM, taking into account the 7C, p, w, r;v(O+, I= 0, m 11v= 1070 MeV) and (0+, I= 0, m 6 = 416 MeV), and showed that S-wave phase shifts can be reproduced, as well as other phase shifts associated with higher partial waves. 4 >' 5 > As is well known, the 1 S 0 phase shift becomes negative at energies higher than about 250 MeV, representing a repulsive interaction at a close internucleon distance. In those works, this has been explained in terms of the vector-meson (especially w) -exchange contri­ bution. (Reference 4 will be called paper U hereafter.) However, there is some criticism of it. The exchange of some other mesons with higher spin and heavier mass gives forces with the opposite sign to that for the vector-meson. f embodies just such a property. 6 > Consequently there is a possibility that repulsive interaction arising from the vector-meson-exchange might be canceled by f. In this paper, we consider an OBEM including fin addition to the 7C, p, w, r;v and 0. These are all established mesons except for (). Here is used as a representation of that part of the two-pion-exchange contribution in which the two pions are in an S state with isospin zero. 7 > For the problem on a nucleon-nucleon interaction at a close internucleon distance, the S and P waves up to the Ge V region provide important information. In this energy region a dynamical calculation should include relativistic effects,