Antinucleon as a probe of nuclear spin and isospin excitations

Abstract

Using two models for the antinucleon-nucleon ($\overline{\mathrm{N}}\mathrm{N}$) interaction, we obtain complex, energy dependent $\overline{\mathrm{N}}\mathrm{N}$ transition operators $t$ appropriate for ($\overline{\mathrm{N}}, {\overline{\mathrm{N}}}^{\ensuremath{'}}$) inelastic scattering studies on complex nuclei. It is shown that the spin-isospin dependence of the $\overline{\mathrm{N}}\mathrm{N}$ annihilation potential plays an important role in determining the dominant spin-isospin modes in the nuclear response. In particular, for the most realistic of our $\overline{\mathrm{N}}\mathrm{N}$ models, a large spin dependent component ${t}_{\ensuremath{\sigma}}$ is obtained, leading to the strong excitation of isoscalar spin-flip states; this term is suppressed in the corresponding NN $t$ matrix. The central spin and isospin independent term, ${t}_{0}^{c}$, is large for $\overline{\mathrm{N}}\mathrm{N}$, at all relevant momentum transfers $q$. At high $q$ the isoscalar spin-orbit (${t}_{0}^{\mathrm{LS}}$) and isovector tensor (${t}_{\ensuremath{\tau}}^{T}$) components are important. Cross section and analyzing power predictions for $\overline{\mathrm{N}}$ inelastic scattering as well as corrections due to energy and density dependence are discussed.