The invariant mass spectra of the ppπ − 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 ppπ − 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 N N -decoupled N N π pseudoscalar resonance with T = 0 called d ′ .
IntroductionIn this paper the spectrum is analysed of invariant masses of the ppπ − system, produced in Double Charge eXchange (DCX) reactions of π + -mesons on the nuclei 107 Ag and 109 Ag in photoemulsion; a peak has been revealed at M ppπ − ≈ 2.05 GeV. We consider this result to confirm the existence of the d ′ , that was proposed in order to explain the maxima exhibited by the forward angle DCX cross section πThe energy of the incident π + -mesons in the photoemulsion experiment was quite low: T π + = 40 ÷ 140 MeV, while the resolution in the invariant mass M ppπ − amounted *