Contribution of the second kind of meson exchange current to pion-nucleus double-charge-exchange reactions 18O( pi +, pi -) 18Ne(g.s) and 14C( pi +, pi -)14Og.s.

Abstract

Based on the Lagrangian of Olsson and Turner, contributions of the second kind of meson exchange current to pion-nucleus double-charge-exchange reactions $^{18}\mathrm{O}$(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${)}^{18}$${\mathrm{N}}_{\mathit{e}(\mathrm{g}.\mathrm{s}))}$ and $^{14}\mathrm{C}$(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$${)}^{14}$${\mathrm{O}}_{\mathrm{g}.\mathrm{s}.}$ have been evaluated. The calculated results show that the second kind of meson exchange current makes the forward theoretical cross section closer to the experimental data but the long-standing puzzling problem of the location of the minimum of the angular distribution at the energy of 164 MeV has not been solved.