Possible exotic resonance effects in two-photon—two-nucleon processes

Abstract

The discussion is given of a structure in the cross section of double-photon production pp --~ 2~/X below the pion threshold, observed recently by the Dib27 Collaboration (JINR) and interpreted as a positive indication of the excitation of an exotic NN-decoupled resonance in this reaction, as well as of the related questions on possible exotic resonance effects in elastic Compton scattering on the deuteron and radiative pion capture in the pionic deuterium.

On evidence for exotic dibaryon d 1* (1956) in selected two-nucleon-two-photon reactions

“…The emphasis was made there on the isoscalar resonances with quantum numbers I = 0, J P = 0 ± , 1 − . Continuing our earlier line of discussion [18], we focus here on the d * 1 (I = 1, J P = 1 + )-resonance and present some additional comments aiming to attract more attention to the speciˇcs of the explication of this resonance in the energy range pertinent to the forthcoming new data on the Compton scattering from deuteron and 3 He. We have in view the ongoing investigation of the γd reaction in MAXLab, where the tagged-photon facility will be used to measure the scattered photon angular distribution between 60 and 150 • over the photon energy range 60−115 MeV in 5 MeV steps [19].…”