Electroexcitation of nucleon resonances
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| Title: | Electroexcitation of nucleon resonances |
|---|---|
| Authors: | Aznauryan, I.G.1,2, Burkert, V.D.1 burkert@jlab.org |
| Source: | Progress in Particle & Nuclear Physics. Jan2012, Vol. 67 Issue 1, p1-54. 54p. |
| Subjects: | Particles (Nuclear physics), Nuclear excitation, Resonance, Quantum chromodynamics, Quark models, Protons |
| Abstract: | Abstract: We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. We describe current experimental facilities, the experiments performed on and electroproduction off protons, and theoretical approaches used for the extraction of resonance contributions from the experimental data. The status of , , and electroproduction is also presented. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of up to and 4.5 GeV 2 for , and , , respectively. These results have been confronted with calculations based on lattice QCD, large- relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the indicate large pion-cloud contributions at low and do not show any sign of approaching the pQCD regime for . Measured for the first time, the electroexcitation amplitudes of the Roper resonance, , provide strong evidence for this state as a predominantly radial excitation of a three-quark (3) ground state, with additional non-3-quark contributions needed to describe the low behavior of the amplitudes. The longitudinal transition amplitude for the was determined and has become a challenge for quark models. Explanations may require large meson-cloud contributions or alternative representations of this state. The clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at , confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented. [Copyright &y& Elsevier] |
| Copyright of Progress in Particle & Nuclear Physics is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 67249033 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Electroexcitation of nucleon resonances – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Aznauryan%2C+I%2EG%2E%22">Aznauryan, I.G.</searchLink><relatesTo>1,2</relatesTo><br /><searchLink fieldCode="AR" term="%22Burkert%2C+V%2ED%2E%22">Burkert, V.D.</searchLink><relatesTo>1</relatesTo><i> burkert@jlab.org</i> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Progress+in+Particle+%26+Nuclear+Physics%22">Progress in Particle & Nuclear Physics</searchLink>. Jan2012, Vol. 67 Issue 1, p1-54. 54p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Particles+%28Nuclear+physics%29%22">Particles (Nuclear physics)</searchLink><br /><searchLink fieldCode="DE" term="%22Nuclear+excitation%22">Nuclear excitation</searchLink><br /><searchLink fieldCode="DE" term="%22Resonance%22">Resonance</searchLink><br /><searchLink fieldCode="DE" term="%22Quantum+chromodynamics%22">Quantum chromodynamics</searchLink><br /><searchLink fieldCode="DE" term="%22Quark+models%22">Quark models</searchLink><br /><searchLink fieldCode="DE" term="%22Protons%22">Protons</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. We describe current experimental facilities, the experiments performed on and electroproduction off protons, and theoretical approaches used for the extraction of resonance contributions from the experimental data. The status of , , and electroproduction is also presented. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of up to and 4.5 GeV 2 for , and , , respectively. These results have been confronted with calculations based on lattice QCD, large- relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the indicate large pion-cloud contributions at low and do not show any sign of approaching the pQCD regime for . Measured for the first time, the electroexcitation amplitudes of the Roper resonance, , provide strong evidence for this state as a predominantly radial excitation of a three-quark (3) ground state, with additional non-3-quark contributions needed to describe the low behavior of the amplitudes. The longitudinal transition amplitude for the was determined and has become a challenge for quark models. Explanations may require large meson-cloud contributions or alternative representations of this state. The clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at , confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Progress in Particle & Nuclear Physics is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.ppnp.2011.08.001 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 54 StartPage: 1 Subjects: – SubjectFull: Particles (Nuclear physics) Type: general – SubjectFull: Nuclear excitation Type: general – SubjectFull: Resonance Type: general – SubjectFull: Quantum chromodynamics Type: general – SubjectFull: Quark models Type: general – SubjectFull: Protons Type: general Titles: – TitleFull: Electroexcitation of nucleon resonances Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Aznauryan, I.G. – PersonEntity: Name: NameFull: Burkert, V.D. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 01 Text: Jan2012 Type: published Y: 2012 Identifiers: – Type: issn-print Value: 01466410 Numbering: – Type: volume Value: 67 – Type: issue Value: 1 Titles: – TitleFull: Progress in Particle & Nuclear Physics Type: main |
| ResultId | 1 |
