Spin and Multipole Decompositions of the Calcium -40 Continuum

The purpose of this work is to determine the spin and multipole compositions of the ^{40 }Ca continuum. Angular distributions of the double-differential cross section d^2 sigma /dOmega dE (sigma) and the spin-flip probability S_{nn } have been measured for inclusive proton scattering of 318 MeV polarized protons from ^{40 }Ca. Data have been acquired over the excitation energy range 6 MeV<=qomega<=q 47 MeV for laboratory scattering angles of 7 ^circ, 10.5^circ , 12^circ, 14 ^circ, 16^circ , 18^circ, 20 ^circ, and 23^circ and over the range 6 MeV<=qomega <=q39 MeV for laboratory scattering angles of 3.5^circ, 5^ circ, and 9^circ (corresponding to momentum transfers from 0.26 to 1.65 fm^{-1}). Multipole decompositions have been performed on the spin-flip and the estimated DeltaS = 0 cross sections. Strength distributions calculated for DeltaL = 1, 2, 3 and the sum of DeltaL = 4 and DeltaL = 5 for both DeltaS = 0 and DeltaS = 1 were compared with the Suzuki energy-weighted sum rules (EWSR). The distribution of deduced giant dipole strength exhausts 158 +/- 16% of the EWSR in the range 6 MeV<=qomega<=q25.4 MeV and peaks around 20 MeV. The giant quadrupole resonance is observed peaked near 18 MeV and exhausts 126 +/- 14% of the EWSR in the range 9.6 MeV <=qomega<=q31.8 MeV. The DeltaS = 0, DeltaL = 3 exhausts 161 +/- 13% of the EWSR over the range 6 MeV<=qomega<=q 47 MeV. This strength is uniformly distributed across the spectrum with no resonance detected. The theoretical angular distributions include distortions nearly exactly, with a small angle approximation for the tensor exchange force. The spin dipole is observed peaked near 20 MeV and exhausts 296 +/- 22% of the EWSR in the range 6 MeV <=qomega<=q 39 MeV. The spin quadrupole peaks around 33 MeV and exhausts 139 +/- 43% of the EWSR in the range 6 MeV <=qomega<=q 39 MeV. The spin octupole strength is uniformly distributed across the spectrum, exhausting 60 +/- 28% of the EWSR with no resonance detected. The over exhaustion of the EWSR will be discussed.