Analyzing power and differential cross section at 9.9, 11.9 and 13.9 MeV for Ca(n, n)Ca

Abstract

The analyzing power and differential cross section for elastic neutron scattering from calcium have been measured at 9.9, 11.9 and 13.9 MeV using the 2H(d, n) 3He source reaction and neutron time-of-flight (t.o.f.) techniques to detect the scattered neutrons. Polarized neutron beams were produced via the polarization transfer reaction 2H( d , n ) 3He at θ = 0°. The data have been corrected for finite geometry and multiple scattering effects. None of the global neutron-nucleus optical model parameter sets usually referred to in the literature reproduces the present cross-section and analyzing power data. Individual as well as energy-averaged fits of the data resulting from new optical model searches are presented. It is shown that the quoted uncertainties of a recent empirical determination of the real part Δ V c of the Coulomb correction term are probably underestimated. Our imaginary Coulomb correction term Δ W c agrees quite well with both a very recent empirical determination and theoretical studies. Although the quality of the fits to the data can be improved by adding l-dependent potentials to the general optical potential, no definite conclusions can be drawn from the present data as to whether or not l-dependent potentials are important in neutron-calcium scattering in the energy range investigated. The data have also been analyzed using a Fourier-Bessel series description of the real central optical potential. Comparing the X 2 values, the experimental data are better reproduced by the Fourier-Bessel method than by our Woods-Saxon optical model analyses. The Fourier-Bessel potentials obtained show strong deviations from the standard Woods-Saxon shape but are in good agreement with calculations using the nuclear structure approach.