The E2/M1 ratio in {Delta} photoproduction

Conference · Fri Aug 01 04:00:00 EDT 1997

OSTI ID:642742

Sandorfi, A M ^[1]; Blanpied, G ^[2]; Blecher, M ^[3]

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1. Brookhaven National Lab., Upton, NY (United States). Physics Dept.
2. Univ. of South Carolina, Columbia, SC (United States). Dept. of Physics
3. Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Physics Dept.; and others

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).

• Research Organization: Brookhaven National Lab., Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Energy Research, Washington, DC (United States)
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 642742
• Report Number(s): BNL--64648; CONF-970526--; ON: DE98000315
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CROSS SECTIONS
DELTA-1232 BARYONS
HYDROGEN 1 TARGET
MIXING RATIO
MULTIPOLE TRANSITIONS
PARTICLE MODELS
PARTICLE STRUCTURE
PHOTONUCLEAR REACTIONS
PHOTOPRODUCTION
PIONS
POLARIZED BEAMS