E-89-037 Electroproduction of the P33(1232) Resonance

Spokespersons

V. Burkert, R. Minehart

Year

2002

Abstract

Models of baryon structure predict a small quadrupole deformation of the nucleon due to residual tensor forces between quarks or distortions from the pion cloud. Sensitivity to quark versus pion degrees of freedom occurs through the Q² dependence of the magnetic ($M_{1+}$), electric ($E_{1+}$), and scalar ($S_{1+}$) multipoles in the γ^* p -> Δ⁺ -> p π⁰ transition. We report new experimental set abstract = for the ratios $E_{1+}/M_{1+}$ and $S_{1+}/M_{1+}$ over the range Q²= 0.4 - 1.8 GeV², extracted from precision p(e,e'p)π⁰ data using a truncated multipole expansion. Results are best described by recent unitary models in which the pion cloud plays a dominant role.

Comment

Release 1 - Data replay: recsis prod-1-9. RC and acceptance: aao_rad+MAID98

Publication

1. K. Joo, L. C. Smith, V. D. Burkert, R. Minehart, I. G. Aznauryan, L. Elouadrhiri, S. Stepanyan, and CLAS Collaboration Q² Dependence of Quadrupole Strength in the γ^*p --> Δ⁺(1232) --> pπ⁰ Transition // Phys. Rev. Let. 88, 122001 (2002)

Quantities

dσ/dΩ

Measurements