dorsal/arxiv
View SchemaQuantum interferences in the $\gamma N \to e^+e^- N$ reaction close to the vector meson production threshold
| Authors | Matthias F. M. Lutz, Madeleine Soyeur |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/0503087 |
| URL | https://arxiv.org/abs/nucl-th/0503087 |
| DOI | 10.1016/j.nuclphysa.2005.05.199 |
| Journal | Nucl.Phys.A760:85-109,2005 |
Abstract
The exclusive photoproduction of $e^+e^-$ pairs from nucleons close to the vector meson production threshold ($1.4<\sqrt s <1.8$ GeV) results from two main processes: the emission of Bethe-Heitler pairs and the photoproduction of $\rho^0$- and $\omega$-mesons decaying into $e^+e^-$ pairs. The Bethe-Heitler amplitudes are purely electromagnetic and reflect mostly the nucleon magnetic structure. The $\gamma N\to e^+e^- N$ amplitudes arising from vector meson production and decay are derived from $\gamma N\to \rho^0 N$ and $\gamma N \to \omega N$ amplitudes supplemented by the Vector Meson Dominance assumption. The vector meson photoproduction amplitudes are calculated using a relativistic and unitary coupled-channel approach to meson-nucleon scattering. They depend sensitively on the coupling of vector fields to baryon resonances. The $\gamma N \to e^+e^- N$ differential cross sections display interference patterns. The interference of Bethe-Heitler pair production with vector meson $e^+e^-$ decay is quite small in the domain of validity of our model for all angles of the emitted $e^+e^-$ pair. The interference of $\rho^0$- and $\omega$-mesons in the $e^+e^-$ channel can be large. It is constructive for the $\gamma p \to e^+e^- p$ reaction and destructive for the $\gamma n \to e^+e^- n$ reaction. We discuss the shape and magnitude of the $e^+e^-$ pair spectra produced in the $\gamma p \to e^+e^- p$ and $\gamma n \to e^+e^- n$ reactions as functions of the pair emission angle and of the total center of mass energy $\sqrt s$.
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"abstract": "The exclusive photoproduction of $e^+e^-$ pairs from nucleons close to the\nvector meson production threshold ($1.4\u003c\\sqrt s \u003c1.8$ GeV) results from two\nmain processes: the emission of Bethe-Heitler pairs and the photoproduction of\n$\\rho^0$- and $\\omega$-mesons decaying into $e^+e^-$ pairs. The Bethe-Heitler\namplitudes are purely electromagnetic and reflect mostly the nucleon magnetic\nstructure. The $\\gamma N\\to e^+e^- N$ amplitudes arising from vector meson\nproduction and decay are derived from $\\gamma N\\to \\rho^0 N$ and $\\gamma N \\to\n\\omega N$ amplitudes supplemented by the Vector Meson Dominance assumption. The\nvector meson photoproduction amplitudes are calculated using a relativistic and\nunitary coupled-channel approach to meson-nucleon scattering. They depend\nsensitively on the coupling of vector fields to baryon resonances. The $\\gamma\nN \\to e^+e^- N$ differential cross sections display interference patterns. The\ninterference of Bethe-Heitler pair production with vector meson $e^+e^-$ decay\nis quite small in the domain of validity of our model for all angles of the\nemitted $e^+e^-$ pair. The interference of $\\rho^0$- and $\\omega$-mesons in the\n$e^+e^-$ channel can be large. It is constructive for the $\\gamma p \\to e^+e^-\np$ reaction and destructive for the $\\gamma n \\to e^+e^- n$ reaction. We\ndiscuss the shape and magnitude of the $e^+e^-$ pair spectra produced in the\n$\\gamma p \\to e^+e^- p$ and $\\gamma n \\to e^+e^- n$ reactions as functions of\nthe pair emission angle and of the total center of mass energy $\\sqrt s$.",
"arxiv_id": "nucl-th/0503087",
"authors": [
"Matthias F. M. Lutz",
"Madeleine Soyeur"
],
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"doi": "10.1016/j.nuclphysa.2005.05.199",
"journal_ref": "Nucl.Phys.A760:85-109,2005",
"title": "Quantum interferences in the $\\gamma N \\to e^+e^- N$ reaction close to the vector meson production threshold",
"url": "https://arxiv.org/abs/nucl-th/0503087"
},
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