We measured missing mass spectrum of the C12(γ,p) reaction for the first time in coincidence with potential decay products from η′ bound nuclei. We tagged an (η+p) pair associated with the η′N→ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observed in the bound-state region. An upper limit of the signal cross section in the opening angle cosθlabηp<-0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η′ production rate. Our results indicate a small branching fraction of the η′N→ηN process and/or a shallow η′-nucleus potential.
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© 2020 American Physical Society.
ASJC Scopus subject areas
- Physics and Astronomy(all)