Coherent photoproduction of the neutral pion and eta meson on the deuteron, γd→ πηd, has been experimentally studied at Eγ< 1.15 GeV. The total cross section as a function of the incident energy shows a rapid increasing behavior below 1 GeV. The existing theoretical calculations well-reproduce the data including final-state interactions. We have measured the differential cross sections dσ/ dMπd, dσ/ dMηd, and dσ/ dΩ d in the γd center-of-mass frame for the first time. An enhancement is observed near the ηd threshold in dσ/ dMηd, suggesting a strong ηd attraction. The enhancement is consistent with a predicted isoscalar 1 -ηNN bound state from the ηNN and πNN coupled-channel calculation.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics