dorsal/arxiv
View SchemaIsospin-Violating Meson-Nucleon Vertices as an Alternate Mechanism of Charge-Symmetry Breaking
| Authors | S. Gardner, C. J. Horowitz, J. Piekarewicz |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9508035 |
| URL | https://arxiv.org/abs/nucl-th/9508035 |
| DOI | 10.1103/PhysRevC.53.1143 |
| Journal | Phys.Rev.C53:1143-1153,1996 |
Abstract
We compute isospin-violating meson-nucleon coupling constants and their consequent charge-symmetry-breaking 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--nucleon vertex dominates the class IV CSB potential obtained from these considerations. We evaluate the resulting spin-singlet--triplet mixing angles, the quantities germane to the difference of neutron and proton analyzing powers measured in elastic $\vec{n}-\vec{p}$ 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 $q^2=0$ 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 $q^2=0$, and we find that omega-meson exchange suffices to explain the measured $n-p$ analyzing power difference~at~183 MeV.
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"abstract": "We compute isospin-violating meson-nucleon coupling constants and their\nconsequent charge-symmetry-breaking nucleon-nucleon potentials. The couplings\nresult from evaluating matrix elements of quark currents between nucleon states\nin a nonrelativistic constituent quark model; the isospin violations arise from\nthe difference in the up and down constituent quark masses. We find, in\nparticular, that isospin violation in the omega-meson--nucleon vertex dominates\nthe class IV CSB potential obtained from these considerations. We evaluate the\nresulting spin-singlet--triplet mixing angles, the quantities germane to the\ndifference of neutron and proton analyzing powers measured in elastic\n$\\vec{n}-\\vec{p}$ scattering, and find them commensurate to those computed\noriginally using the on-shell value of the $\\rho$-$\\omega$ mixing amplitude.\nThe use of the on-shell $\\rho$-$\\omega$ mixing amplitude at $q^2=0$ has been\ncalled into question; rather, the amplitude is zero in a wide class of models.\nOur model possesses no contribution from $\\rho$-$\\omega$ mixing at $q^2=0$, and\nwe find that omega-meson exchange suffices to explain the measured $n-p$\nanalyzing power difference~at~183 MeV.",
"arxiv_id": "nucl-th/9508035",
"authors": [
"S. Gardner",
"C. J. Horowitz",
"J. Piekarewicz"
],
"categories": [
"nucl-th",
"hep-ph"
],
"doi": "10.1103/PhysRevC.53.1143",
"journal_ref": "Phys.Rev.C53:1143-1153,1996",
"title": "Isospin-Violating Meson-Nucleon Vertices as an Alternate Mechanism of Charge-Symmetry Breaking",
"url": "https://arxiv.org/abs/nucl-th/9508035"
},
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