Break-up and Coherent Photoproduction of {eta} Mesons on the Deuteron

We present new break-up and coherent data for {eta} meson photoproduction on the deuteron, using a deuterium target and tagged bremsstrahlung photons up to 1GeV. The differential cross sections for the coherent process were measured from threshold to 800MeV. They are much smaller than those previously reported. The break-up channel provides a direct measurement of the neutron to proton differential cross section ratios. At the S{sub 11}(1535) resonance peak, {sigma}{sub n}/{sigma}{sub p}=0.68{plus_minus}0.06 leading to an isoscalar to isovector amplitude ratio of A{sub s}/A{sub {upsilon}}=0.096{plus_minus}0.02 . {copyright} {ital 1997} {ital The American Physical Society}