Semiexclusive pionic double charge exchange on4He

The semiexclusive reaction ${}^{4}\mathrm{He}({\ensuremath{\pi}}^{+},{\ensuremath{\pi}}^{\ensuremath{-}}pp)pp$ has been studied at pion kinetic energies of 105 MeV and 115 MeV. Signatures from the production of the hypothetical $\ensuremath{\pi}\mathrm{NN}$ resonance ${d}^{\ensuremath{'}}$ have been searched for in the invariant mass ${M}_{\ensuremath{\pi}\mathrm{pp}}$ spectra. No hint for a dominant ${d}^{\ensuremath{'}}$ production, as anticipated from double charge exchange excitation functions on nuclei, has been found. The data are satisfactorily described by sequential single charge exchange.