The use of quasielastic pion-proton backward scattering at 0.7 GeV/c for studying Fermi motion in light nuclei

The plane-wave approximation was used to examine the proton Fermi-momentum distribution in experiments on quasielastic large-momentum-transfer pion-nucleon scattering in light nuclei ⁶Li, ⁷Li, and ¹²C. It was found that, unlike the (e, e′) reaction, the Fermi-gas model is in poor agreement with experiment, whereas the oscillator model adequately describes the spectrum shape. However, the parameters obtained for these distributions are sizably smaller than those derived from the (e, e′)) experiments. This suggests that the plane-wave approach is inadequate and that more complicated theoretical approaches, supposedly allowing for pion-nucleon amplitude modification in nuclear matter, are necessary for the analysis of experimental data.