The E2/M1 ratio in {Delta} photoproduction

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The properties of the transition from the nucleon to the {Delta}(1232) serve as a benchmark for models of nucleon structure. To first order, N {r_arrow} {Delta} photo-excitation is dominated by a simple M1 quark spin-flip transition. At higher order, small L = 2 components in the N and {Delta} wavefunctions allow this excitation to proceed via an electric quadrupole transition. Since Nucleon models differ greatly on the mechanisms used to generate these L = 2 components,, the ratio of E2/M1 transitions (EMR) provides a sensitive test for structure models. Here, new high-precision measurements of p({rvec {gamma}}, {pi}) and p({rvec {gamma}}, … continued below

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12 p.

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Sandorfi, A.M.; Blanpied, G.; Blecher, M. & Collaboration, LEGS August 1, 1997.

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  • Sandorfi, A.M. Brookhaven National Lab., Upton, NY (United States). Physics Dept.
  • Blanpied, G. Univ. of South Carolina, Columbia, SC (United States). Dept. of Physics
  • Blecher, M. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Physics Dept.
  • Collaboration, LEGS

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Description

The properties of the transition from the nucleon to the {Delta}(1232) serve as a benchmark for models of nucleon structure. To first order, N {r_arrow} {Delta} photo-excitation is dominated by a simple M1 quark spin-flip transition. At higher order, small L = 2 components in the N and {Delta} wavefunctions allow this excitation to proceed via an electric quadrupole transition. Since Nucleon models differ greatly on the mechanisms used to generate these L = 2 components,, the ratio of E2/M1 transitions (EMR) provides a sensitive test for structure models. Here, new high-precision measurements of p({rvec {gamma}}, {pi}) and p({rvec {gamma}}, {gamma}) cross sections and beam asymmetries have been combined with other polarization ratios in a simultaneous analysis of both reactions. Compton scattering has provided two important new constraints on the photo-pion amplitude. The E2/M1 mixing ratio for the N {r_arrow} {Delta} transition extracted from this analysis is EMR = {minus}3.0% {+-} 0.3 (stat+sys) {+-} 0.2 (model).

Physical Description

12 p.

Notes

INIS; OSTI as DE98000315

Source

  • International conference on quark lepton nuclear physics (QULEN): Nonperturbative QCD hadron physics and electroweak nuclear processes, Osaka (Japan), 20-23 May 1997

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  • Other: DE98000315
  • Report No.: BNL--64648
  • Report No.: CONF-970526--
  • Grant Number: AC02-76CH00016
  • Office of Scientific & Technical Information Report Number: 642742
  • Archival Resource Key: ark:/67531/metadc697977

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  • August 1, 1997

Added to The UNT Digital Library

  • Aug. 14, 2015, 8:43 a.m.

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  • Nov. 6, 2015, 11:49 p.m.

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Sandorfi, A.M.; Blanpied, G.; Blecher, M. & Collaboration, LEGS. The E2/M1 ratio in {Delta} photoproduction, article, August 1, 1997; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc697977/: accessed March 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.

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