dorsal/arxiv
View SchemaNucleon Resonance Excitation with Virtual Photons
| Authors | L. Tiator, S. Kamalov |
|---|---|
| Categories | |
| ArXiv ID | nucl-th/0610113 |
| URL | https://arxiv.org/abs/nucl-th/0610113 |
| DOI | 10.1063/1.2734304 |
| Journal | AIPConf.Proc.904:191-202,2007 |
Abstract
The unitary isobar model MAID is used for a partial wave analysis of pion photoproduction and electroproduction data on the nucleon. In particular we have taken emphasis on the region of the Delta(1232) resonance and have separated the resonance and background amplitudes with the K-matrix approach. This leads to electromagnetic properties of the dressed Delta resonance, where all multipole amplitudes become purely imaginary and all form factors and helicity amplitudes become purely real at the K-matrix pole of W=M_Delta=1232 MeV. The REM=E2/M1 and RSM=C2/M1 ratios of the quadrupole excitation are compared to recent data analysis of different groups. The REM ratio of MAID2005 agrees very well with the data and has a linear behavior over the whole experimentally explored Q^2 region with a small positive slope that predicts a zero crossing around 3.5 GeV^2. The recent RSM data for Q^2 < 0.2 GeV^2 indicate a qualitative change in the shape of the ratio which can be explained by the impact of the Siegert theorem at pseudothreshold (Q^2=-0.086 GeV^2) in the unphysical region.
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"abstract": "The unitary isobar model MAID is used for a partial wave analysis of pion\nphotoproduction and electroproduction data on the nucleon. In particular we\nhave taken emphasis on the region of the Delta(1232) resonance and have\nseparated the resonance and background amplitudes with the K-matrix approach.\nThis leads to electromagnetic properties of the dressed Delta resonance, where\nall multipole amplitudes become purely imaginary and all form factors and\nhelicity amplitudes become purely real at the K-matrix pole of W=M_Delta=1232\nMeV. The REM=E2/M1 and RSM=C2/M1 ratios of the quadrupole excitation are\ncompared to recent data analysis of different groups. The REM ratio of MAID2005\nagrees very well with the data and has a linear behavior over the whole\nexperimentally explored Q^2 region with a small positive slope that predicts a\nzero crossing around 3.5 GeV^2. The recent RSM data for Q^2 \u003c 0.2 GeV^2\nindicate a qualitative change in the shape of the ratio which can be explained\nby the impact of the Siegert theorem at pseudothreshold (Q^2=-0.086 GeV^2) in\nthe unphysical region.",
"arxiv_id": "nucl-th/0610113",
"authors": [
"L. Tiator",
"S. Kamalov"
],
"categories": [
"nucl-th"
],
"doi": "10.1063/1.2734304",
"journal_ref": "AIPConf.Proc.904:191-202,2007",
"title": "Nucleon Resonance Excitation with Virtual Photons",
"url": "https://arxiv.org/abs/nucl-th/0610113"
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