19 research outputs found
Non-strange Dibaryon Resonances Observed in the Reaction
Coherent double neutral-pion photoproduction on the deuteron,
{}, has been experimentally studied at incident
photon energies ranging from 0.75 to 1.15 GeV. The total cross section as a
function of the center-of-mass energy shows resonance-like
behavior, which peaks at approximately 2.47 and 2.63 GeV. The measured angular
distribution of deuteron emission is rather flat, which cannot be reproduced by
the kinematics of quasi-free production with deuteron coalescence.
In invariant-mass distributions, a clear peak is observed at
GeV with a width of GeV. The
spin-parity of this state is restricted to , or from the
angular distributions of the two s. The present work shows strong
evidence for the existence of an isovector dibaryon resonance with a mass of
2.14 GeV. The assignment is consistent with the theoretically
predicted state, and also with the energy dependence of the
partial-wave amplitude for the
{} and {} reactions.Comment: 12 pages, 6 figure