Isospin-violating meson-nucleon vertices as an alternate mechanism of charge-symmetry breaking
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (United States)
- Nuclear Theory Center and Department of Physics, Indiana University, Bloomington, Indiana 47505 (United States)
- Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States)
We compute isospin-violating meson-nucleon coupling constants and their consequent charge-symmetry-breaking (CSB) nucleon-nucleon potentials. The couplings result from evaluating matrix elements of quark currents between nucleon states in a nonrelativistic constituent quark model; the isospin violations arise from the difference in the up and down constituent quark masses. We find, in particular, that isospin violation in the omega-meson{endash}nucleon vertex dominates the class IV CSB potential obtained from these considerations. We evaluate the resulting spin-singlet{endash}triplet mixing angles, the quantities germane to the difference of neutron and proton analyzing powers measured in elastic {ital n}{searrow}-{ital p}{searrow} scattering, and find them commensurate to those computed originally using the on-shell value of the {rho}-{omega} mixing amplitude. The use of the on-shell {rho}-{omega} mixing amplitude at {ital q}{sup 2}=0 has been called into question; rather, the amplitude is zero in a wide class of models. Our model possesses no contribution from {rho}-{omega} mixing at {ital q}{sup 2}=0, and we find that omega-meson exchange suffices to explain the measured {ital n}-{ital p} analyzing power difference at 183 MeV. {copyright} {ital 1996 The American Physical Society.}
- Research Organization:
- Indiana Univ., Bloomington, IN (United States)
- DOE Contract Number:
- FG02-87ER40365; FG05-85ER25000; FG05-92ER40750
- OSTI ID:
- 283407
- Journal Information:
- Physical Review, C, Vol. 53, Issue 3; Other Information: PBD: Mar 1996
- Country of Publication:
- United States
- Language:
- English
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