Abstract

Purpose. This article is dedicated to the study of phase shifts for single-channel neutron-proton scattering. The phase shifts, which are obtained in the variable phase approach, are studied. For the approximation of phase shifts, a function is used in the form of a known formula for a parabolic-type quadratic function y(x)=a+bx+cx², which was proposed by M.A. Dolgopolov, L.A. Minin and V.A. Rabotkin in the study of phase shifts for the Paris potential. It is necessary to find the coefficients a, b, c for y(x) when approximating the np- scattering phases for the Argonne v18 potential.
Methods. Approximation is used to find the coefficients of the function y(x). Find the optimal values of the coefficients a, b, c at a minimum value χ².
Results. An approximation of the neutron-proton scattering phases obtained by various methods for the phenomenological nucleon-nucleon potential Argonne v18 was made. The calculated coefficients of this function obtained for phase shifts by means of the variable phase approach are compared with the results of the approximation of the scattering phases from the original paper. For illustration graphs are given for phase shifts for four spin states for the np- system (¹S₀, ³P₁, ¹D₂, ³D₂).
Conclusions. The obtained coefficients for the function y(x) can be used to calculate the values of the scalar scattering amplitude, the full cross-section and the partial scattering amplitude for any phase value within the energy interval for the approximation carried out. In next studies one can obtain and compare the coefficients and parameters of approximation for scattering phases for other modern phenomenological nucleon-nucleon potentials
 

Keywords: variable phase approach, nucleon-nucleon scattering, approximation, phase shifts, Argonne v18 potential

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