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Search for quadrupole strength in the electroexcitation of the delta+(1232) |
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| Authors: | Mertz C Vellidis C E Alarcon R Barkhuff D H Bernstein A M Bertozzi W Burkert V Chen J Comfort J R Dodson G Dolfini S Dow K Farkhondeh M Finn J M Gilad S Gothe R W Jiang X Joo K Kaloskamis N I Karabarbounis A Kelly J J Kowalski S Kunz C Lourie R W McIntyre J I Milbrath B D Miskimen R Mitchell J H Papanicolas C N Perdrisat C F Sarty A J Shaw J Soong S B Tieger D Tschalaer C Turchinetz W Ulmer P E Van Verst S Warren G A Weinstein L B Williamson S Woo R J Young A |
| Institution: | Department of Physics and Astronomy, Arizona State University, tempe 85287, USA. |
| Abstract: | High-precision 1H(e,e'p)pi(0) measurements at Q2 = 0.126 (GeV/c)2 are reported, which allow the determination of quadrupole amplitudes in the gamma*N-->Delta transition; they simultaneously test the reliability of electroproduction models. The derived quadrupole-to-dipole ( I = 3/2) amplitude ratios, R(SM) = (-6.5+/-0.2(stat+sys)+/-2.5(mod))% and R(EM) = (-2.1+/-0.2(stat+sys)+/-2.0(mod))%, are dominated by model error. Previous R(SM) and R(EM) results should be reconsidered after the model uncertainties associated with the method of their extraction are taken into account. |
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