Signature of a π<i>NN</i>resonance in pionic double charge exchange at low energies

Abstract

All currently available data on the pionic double charge exchange reaction (${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$) on nuclei exhibit a very peculiar energy dependence near ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=50 MeV, while the angular distributions behave quite regularly. We demonstrate that these features find their natural explanation by a narrow resonance in the \ensuremath{\pi}NN subsystem with ${\mathit{J}}^{\mathit{P}}$=${0}^{\mathrm{\ensuremath{-}}}$ and a mass of 2.065 GeV.