Near-threshold photoproduction of η-mesons from the deuteron

Coherentπ0π0photoproduction on lightest nuclei

“…In the latter case, according to the results of Refs. [16][17][18][19] the value of α is close to 0.1. Due to the same reason the cross section for coherent π 0 π 0 photoproduction on nuclei should have much in common with that for η photoproduction.…”

“…[18] and [20], give for the ratio σ γ 3 He→η 3 He /σ γd→ηd in the region of S 11 (1535) the value about 20. The experimental results for the γd → ηd and γ 3 He→ η 3 He cross sections [16,21] indicate, that this ratio is likely to be essentially smaller, about 4. This difference is primarily due to larger value of the deuteron cross section in comparison to that predicted by the model of [18] in which the possible nontrivial phase between the neutron and the proton amplitudes is neglected (see discussion after Eq.…”

Production of η and η′ mesons on nucleons and nuclei

“…Early experiments measured only the inclusive reaction γd → η(np) (without the detection of recoil nucleons) [51] or detected only the recoil nucleons using missing-mass analysis [52]. The first fully exclusive measurement, which already used a complete reconstruction of the final state kinematics to remove the Fermi motion effects, was done in the threshold region [53].…”

“…We now discuss in greater detail the results for η and η production. Inclusive photoproduction of η mesons from nuclei has been measured for the deuteron [43,51,52,53,55], for 3 He [45], and for heavier nuclei such as 12 C, 40 Ca, 63 Cu, 93 Nb, nat Pb [151,152,158,159] at MAMI, at KEK, in Tohoku, and at ELSA. In general, the agreement between the different measurements is good (see comparisons in [152]).…”

“…This has been exploited for η production, where measurements of the breakup reaction [51,52,53] revealed a neutron/proton cross section ratio of 2/3. According to Eq.…”