Pion Elastic and Inelastic Scattering from Nitrogen -15

Data were obtained on the Clinton P. Anderson Los Alamos Meson Physics Facility Energetic Pion Channel and Spectrometer for elastic and inelastic pion scattering from ground state nitrogen 15 nuclei. States observed here included those of 0.0, 5.27, 6.32, 7.16, 7.30, 7.57, 8.31, 8.57, 9.15, 9.76, 9.9, 10.7, 11.3, 11.9, 12.5, 12.9, 13.1, 14.1, 14.4, 14.6, 15.0, 16.5, 16.9, 17.2, 17.6, 18.3, 18.7, and 18.9 MeV excitation energies. Angular distributions were obtained for scattering at angles from 25 ^circ to 90^circ in 5^circ increments with an incident pion energy of 164 MeV. Optical model analyses of the elastic (0 MeV) angular distributions with equal point proton and neutron densities in both momentum and coordinate space formulations accurately predict the data, although the two formulations require different energy shifts to do so. This difference is thought to be a result of the momentum space code's more accurate nonlocal representation of the nuclear potential. Additional spectra were obtained for scattering at constant momentum transfers of.94 and 1.57 fm^{-1} in order to generate constant momentum transfer excitation functions. Use of these excitation functions, {sigma( pi^+)}over {sigma(pi ^-)}ratios, and shell model DWIA calculations allowed identification of several excited states having shell-model-like, single particle-hole, pure spin-flip excitations. Shell model and collective model DWIA calculations, as well as the q =.94 and 1.57 fm^{ -1} excitation functions and the { sigma(pi^+)}over {sigma( pi^-)}ratios indicate that the other states are generally well represented by a shell model description with collective enhancements.