Complete set of polarization transfer observables for the 16O(p⃗,n⃗)16F{}^{16}{\rm O}(\vec{p},\vec{n}){}^{16}{\rm F} reaction at 296 MeV and 0 degrees

We report measurements of the cross section and a complete set of polarization transfer observables for the ${}^{16}{\rm O}(\vec{p},\vec{n}){}^{16}{\rm F}$ reaction at a bombarding energy of $T_p$ = 296 MeV and a reaction angle of $\theta_{\rm lab}$ = $0^{\circ}$. The data are compared with distorted-wave impulse approximation calculations employing the large configuration-space shell-model (SM) wave functions. The well-known Gamow-Teller and spin-dipole (SD) states at excitation energies of $E_x$ $\lesssim$ 8 MeV have been reasonably reproduced by the calculations except for the spin--parity $J^{\pi}$ = $2^-$ state at $E_x$ = 5.86 MeV. The SD resonance at $E_x$ $\simeq$ 9.5 MeV appears to have more $J^{\pi}$ = $2^-$ strength than $J^{\pi}$ = $1^-$ strength, consistent with the calculations. The data show significant strength in the spin-longitudinal polarized cross section $ID_L(0^{\circ})$ at $E_x$ $\simeq$ 15 MeV, which indicates existence of the $J^{\pi}$ = $0^-$ SD resonance as predicted in the SM calculations.Comment: 6 figures, submitted to Physical Review

Distorted wave impulse approximation analysis for spin observables in nucleon quasi-elastic scattering and enhancement of the spin-longitudinal response

We present a formalism of distorted wave impulse approximation (DWIA) for analyzing spin observables in nucleon inelastic and charge exchange reactions leading to the continuum. It utilizes response functions calculated by the continuum random phase approximation (RPA), which include the effective mass, the spreading widths and the \Delta degrees of freedom. The Fermi motion is treated by the optimal factorization, and the non-locality 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, ID_q and ID_p, of 12C, 40Ca (\vec{p},\vec{n}) at 494 and 346 MeV. The calculation reasonably reproduced the observed ID_q, which is consistent with the predicted enhancement of the spin-longitudinal response function R_L. However, the observed ID_p is much larger than the calculated one, which was consistent with neither the predicted quenching nor the spin-transverse response function R_T obtained by the (e,e') scattering. The Landau-Migdal parameter g'_N\Delta for the N\Delta transition interaction and the effective mass at the nuclear center m^*(r=0) are treated as adjustable parameters. The present analysis indicates that the smaller g'_{N\Delta}(\approx 0.3) and m^*(0) \approx 0.7 m are preferable. We also investigate the validity of the plane wave impulse approximation (PWIA) with the effective nucleon number approximation for the absorption, by means of which R_L and R_T have conventionally been extracted.Comment: RevTex 3, 29 pages, 2 tables, 8 figure