Backward-angle electroproduction of η′ mesons off protons at W = 2.13 GeV and Q 2 = 0.46 (GeV/ c )2

The electroproduction of η′ mesons from a 1H target at W = 2.13GeV, Q2 = 0.46(GeV/c)2 and cos θ CM_γ *η ≈ -1 has been experimentally measured. The differential cross section of virtual-photoproduction has been obtained as 4.4 ± 0.8(stat.) ± 0.4(sys.)nb/sr in the One-Photon-Exchange Approximation. This value is one-sixth of that of real-photoproduction at backward angles. A comparison with newly-developed isobar model calculations not only shows validity of the theoretical framewark employed, but also imposes new constraints on coupling strength between the η′p final state and nucleon resonances.