Resonant behaviour in double charge exchange reaction of ��^+ mesons on the nuclear photoemulsion

The invariant mass spectra of the $pp��^-$ and $pp$ systems produced in the double charge exchange (DCX) of positively charged pions on photoemulsion are analysed. A pronounced peak is observed in the $pp��^-$ invariant mass spectrum, while the $M_{pp}$ spectrum exhibits a strong Migdal-Watson effect of the proton-proton final state interaction. These findings are in favor of the $NN$-decoupled $NN��$ pseudoscalar resonance with T=0 called $d'$.
13 pages, 5 figures, revised version