Distorted wave impulse approximation analysis for spin observables in nucleon quasielastic scattering and enhancement of the spin longitudinal response - art. no. 044609

We present a formalism of distorted wave impulse approximation for analyzin g spin observables in nucleon inelastic and charge-exchange reactions leadi ng to the continuum. It utilizes response functions calculated by the conti nuum random-phase approximation, which include the effective mass, the spre ading widths, and the Delta degrees of freedom. The Fermi motion is treated by the optimal factorization, and the nonlocality of the nucleon-nucleon t matrix by an averaged reaction plane approximation. By using the formalism we calculated the spin-longitudinal and the spin-transverse cross sections , IDq and IDp. of C-12, Ca-40 ((p) over right arrow,(n) over right arrow) a t 494 and 346 MeV. The calculation reasonably reproduced the observed ID,, which is consistent with the predicted enhancement of the spin-longitudinal response function R-L. However, the observed IDp is much larger than the c alculated one, which was consistent with neither the predicted quenching no r the spin-transverse response function R-T obtained by the (e,e') scatteri ng. The Landau-Migdal parameter g(N Delta)' for the N Delta transition inte raction and the effective nucleon mass at the nuclear center m(N)*(r = 0) a re treated as adjustable parameters. The present analysis indicates that th e smaller g(N Delta)'(approximate to 0.3) and m(N)*(0) approximate to 0.7 m (N) are preferable. We also investigate the validity of the plane-wave impu lse approximation with the effective nucleon number approximation for the a bsorption, by means of which R-L and R-T have conventionally been extracted .