Analyzing-power measurements in the 48Ca(p,n)48Sc reaction at 134 MeV.

Abstract

Analyzing-power measurements were performed for the $^{48}\mathrm{Ca}$(p,n${)}^{48}$Sc reaction at 134 MeV in about 6\ifmmode^\circ\else\textdegree\fi{} steps from 0\ifmmode^\circ\else\textdegree\fi{} to 60\ifmmode^\circ\else\textdegree\fi{}. The overall neutron energy resolution varied from about 400 keV for angles out to 42\ifmmode^\circ\else\textdegree\fi{} to about 700 keV at wider angles. Analyzing-power angular distributions were extracted for the (\ensuremath{\pi}${f}_{7/2}$,\ensuremath{\nu}${f}_{7/2}^{\mathrm{\ensuremath{-}}1}$) octet of states, the ${1}^{+}$ Gamow-Teller giant resonance, and the T=4, ${1}^{+}$ state at ${E}_{x}$=16.8 MeV. All of these angular distributions are described reasonably well by ``standard'' distorted-wave impulse approximation calculations. A qualitative difference is observed in the analyzing power between the transitions to the low-lying ${0}^{+}$ and ${1}^{+}$ states compared to the transition to the high-lying ${1}^{+}$ state. This difference appears to be associated with a sensitivity to the predominant particle-hole structure of the final states, viz., (\ensuremath{\pi}${f}_{7/2}$,\ensuremath{\nu}${f}_{7/2}^{\mathrm{\ensuremath{-}}1}$) versus (\ensuremath{\pi}${f}_{5/2}$,\ensuremath{\nu}${f}_{7/2}^{\mathrm{\ensuremath{-}}1}$). This sensitivity is ascribed to the difference in nonlocality contributions to the two different 1p1h excitations. Excitation-energy plots of the analyzing power were extracted at each angle. No characteristic signature of spin-transfer strength is observed in the region of the Gamow-Teller giant resonance.