Measurement of the γpΔ(1236)-vertex form factors

In this letter we report the results of an experiment performed with an external electron beam of the Tokyo 1.3 GeV electron synchrotron. The work is essentially an extension and refinement of a previous study (1) and the observation was made on the protons decaying from the A+(1236) in coincidence with the scattered electrons. The conclusions are i) the contribution of the scalar photon to the production of the A(1236) is negligibly small as compared with the transverse photon and ii) the TpA(1236)vertex form factor shows a dependence similar to the proton form factor on the momentum transfer at least up to q2_~ 8 fm -~. The experimental arrangement is similar to that of the previous work. The electrons inelastically scattered from the protons according to the reaction