Study of Non-strange Dibaryon Resonances Via Coherent Double Neutral-Meson Photoproduction from the Deuteron

The non-strange \(B=2\) system (dibaryon) has been studied using coherent neutral-meson photoproduction from the deuteron, \(\gamma d\rightarrow \pi ^0\pi ^0d\) and \(\gamma d\rightarrow \pi ^0\eta d\), measured with the FOREST detector at the ELPH facility. A rather flat angular distribution of deuteron emission and a peak in the \(\pi ^0d\) invariant-mass distribution give evidence for the 2.15-GeV isovector dibaryon. The excitation function of the total cross section as a function of the \(\gamma d\) center-of-mass energy for the former reaction shows the evidence for the existence of 2.47- and 2.63-GeV isoscalar dibaryons.