Excitation of Unnatural-Parity States inC12by 800-MeV Polarized Protons

Abstract

Cross sections and analyzing powers have been measured for 800-MeV proton inelastic transitions to unnatural-parity states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$. Data for the 15.11-MeV $1^{+}$, $T=1\mathrm{}$ state are well explained by a distorted-wave impulse-approximation calculation based on proton-neutron charge-exchange cross sections. Negative analyzing powers were observed for the first time at 800 MeV, for the 12.71-MeV $1^{+}$, $T=0\mathrm{}$ state. Values of $A_y$ appear to be characteristic of the isospin transfer, and support isospin assignments for states at 18.3 and 19.4 MeV.