New proposal to JLab PAC 27 December 3 , 2004 Structure of the Roper resonance from measurements

We propose to study the structure of the Roper resonance by a measurement of recoil proton polarization components in the p(~e, e′~ p)π0 reaction in Hall A. The components exhibit strong sensitivities to the pertinent resonant Roper multipoles M1− and S1−, and will be measured in a broad range of Q2 and W . The large kinematic coverage will allow us to attain a better overall understanding of the N→ R transition amplitudes, for which only scarce data exist. These measurements will provide critical insight for extracting information on the N → R transition through comparison with the state-of-the-art models, and will also provide severe constraints on these models in the second resonance region. The experiment requires 2GeV and 3GeV beams and the standard hardware configuration of Hall A. We request 348 hours of beam time.