Nucleon-nucleon scattering in the 0–6 GeV range and the relativistic optical model based on deep attractive forbidden state potentials

Abstract

The optical relativistic model based on deep attractive forbidden state quasipotentials describes well the angular and energy dependence of differential np- and pp-scattering cross sections and polarizations, including the transition from the U-shaped form of the angular distributions of np scattering to forward scattering at the energy ${\mathit{E}}_{\mathrm{lab}}$\ensuremath{\ge}1 GeV, when the scattering P-phase shifts, equal to \ensuremath{\pi} at low energies, pass through \ensuremath{\pi}/2 (the triplet and singlet S-phase shifts start from the values 2\ensuremath{\pi} and \ensuremath{\pi}, respectively). The higher scattering phase shifts (L\ensuremath{\ge}2) are small everywhere. The potentials are determined from the scattering phase shifts in the low-energy region ${\mathit{E}}_{\mathrm{lab}}$1 GeV. They have been chosen in the simple Gaussian form and for different partial waves they differ in depth and width (from ${\mathit{V}}_{0}$=0.73 GeV, a=0.85 fm to ${\mathit{V}}_{0}$=2.40 GeV, a=0.45 fm). A few negative phase shifts $^{3}$${\mathit{D}}_{1}$, $^{3}$${\mathit{F}}_{3}$, $^{3}$${\mathit{G}}_{3}$, which reflect the peripheral repulsion due to the spin-orbital and tensor interactions, are calculated by means of the one-boson-exchange potential periphery matched to the central attraction. The imaginary part W of the optical potential V+iW is determined by the value ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{tot}}$/${\mathrm{\ensuremath{\sigma}}}_{\mathrm{el}}$ and grows rapidly with increase in the energy ${\mathit{E}}_{\mathrm{lab}}$, so that the phase-shift values lose sensitivity to the real part V of optical potential if ${\mathit{E}}_{\mathrm{lab}}$ exceeds 5 GeV. Finally, the quantum chromodynamics (QCD) effects are discussed which may underlie the potentials considered.