Pion scattering to 8/sup -/ stretched states in /sup 60/Ni

Abstract

cross sections for pion scattering were measured for ten previously known J* = 8s tretched states in 60 Ni. A possible new pure isoscalar stretched state was also found. The data were taken near the A3,3-resonance using 162 MeV incident pions and scattering angles of 65°, 80°, and 90° for n + and 65°a nd 80° for ir~.For 60 Ni the isoscalar (AT = 0) strength was found to be much smaller than the isovector (AT = 1) strength, as has been found previously in other nuclei, and the isovector strength was found to be only 25% of that expected from a simple sum rule. The isoscalar and isovector amplitudes of each stretched transition were found by comparing the pion scattering cross sections with previous electron scattering data.The analysis of the 60 Ni data found that the use of Woods-Saxon (WS) wave functions in the theoretical calculations gave much better agreement with data than the use of the usual harmonic oscillator (HO) wave functions. The WS theory gave better predictions of: 1) the angle at which the TT~ and n + angular distributions are maximum, 2) the ratios of ir~ to 7r + cross sections for pure isovector states (which were much larger than unity), and 3) the absolute size of the cross sections for all states (so that the normalization factor necessary to arrive at agreement of theory with data was closer to unity). The theoretical calculations used the distorted vi i wave impulse approximation, including new methods for unbound states. at a normalization factor close to unity was found when WS wave functions were consistently used for analyzing both pion and electron inelastic scattering data. This is the first time that a consistent analysis in several nuclei has been done using WS wave functions. ACKNOWLEDGEMENTSThese acknowledgements are for a few of the many people who have assisted in my education. Alamos for assisting in the arrangements for this experiment, and especially