dorsal/arxiv
View SchemaIsospin Violations in the Pion-Nucleon System
| Authors | Jorge Piekarewicz |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/9507030 |
| URL | https://arxiv.org/abs/nucl-th/9507030 |
| DOI | 10.1016/0370-2693(95)01026-M |
| Journal | Phys.Lett.B358:27-33,1995 |
Abstract
We examine the effect of isospin-violating meson-nucleon coupling constants on low-energy pion-nucleon scattering. We compute the couplings in the context of a nonrelativistic quark model. The difference between the up and down constituent masses induces a coupling of the neutral pion to the proton that is slightly larger than the corresponding one for the neutron. This difference generates a large isospin-violating correction---proportional to the isospin-even contribution arising from the nucleon Born terms---to the charge-exchange ($\pi^{-}p \rightarrow \pi^{0}n$) amplitude. In contrast to the isospin-conserving case, this correction is not cancelled by $\sigma$-meson exchange; in our model there is no isospin-violating $NN\sigma$ coupling at $q^2=0$. As a result, we find a violation of the triangle identity consistent with the one reported by Gibbs, Ai, and Kaufmann from a recent analysis of pion-nucleon data.
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"abstract": "We examine the effect of isospin-violating meson-nucleon coupling constants\non low-energy pion-nucleon scattering. We compute the couplings in the context\nof a nonrelativistic quark model. The difference between the up and down\nconstituent masses induces a coupling of the neutral pion to the proton that is\nslightly larger than the corresponding one for the neutron. This difference\ngenerates a large isospin-violating correction---proportional to the\nisospin-even contribution arising from the nucleon Born terms---to the\ncharge-exchange ($\\pi^{-}p \\rightarrow \\pi^{0}n$) amplitude. In contrast to the\nisospin-conserving case, this correction is not cancelled by $\\sigma$-meson\nexchange; in our model there is no isospin-violating $NN\\sigma$ coupling at\n$q^2=0$. As a result, we find a violation of the triangle identity consistent\nwith the one reported by Gibbs, Ai, and Kaufmann from a recent analysis of\npion-nucleon data.",
"arxiv_id": "nucl-th/9507030",
"authors": [
"Jorge Piekarewicz"
],
"categories": [
"nucl-th"
],
"doi": "10.1016/0370-2693(95)01026-M",
"journal_ref": "Phys.Lett.B358:27-33,1995",
"title": "Isospin Violations in the Pion-Nucleon System",
"url": "https://arxiv.org/abs/nucl-th/9507030"
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