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Titolo:
Exchange currents in nucleon electroexcitation - art. no. 035203
Autore:
Meyer, U; Hernandez, E; Buchmann, AJ;
Indirizzi:
Univ Tubingen, Inst Theoret Phys, D-72076 Tubingen, Germany Univ TubingenTubingen Germany D-72076 t Phys, D-72076 Tubingen, Germany Univ Salamanca, Grp Fis Nucl, E-37008 Salamanca, Spain Univ Salamanca Salamanca Spain E-37008 is Nucl, E-37008 Salamanca, Spain
Titolo Testata:
PHYSICAL REVIEW C
fascicolo: 3, volume: 6403, anno: 2001,
pagine: 5203 -
SICI:
0556-2813(200109)6403:3<5203:ECINE->2.0.ZU;2-3
Fonte:
ISI
Lingua:
ENG
Soggetto:
CONSTITUENT-QUARK-MODEL; TRANSITION FORM-FACTORS; N-DELTA TRANSITION; BARYON RESONANCES; ROPER RESONANCE; CHARGE RADII; ELECTROMAGNETIC PROPERTIES; HYPERFINE INTERACTIONS; PION-PHOTOPRODUCTION; MAGNETIC-MOMENT;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
--discip_EC--
Citazioni:
91
Recensione:
Indirizzi per estratti:
Indirizzo: Meyer, U Univ Tubingen, Inst Theoret Phys, Morgenstelle 14, D-72076 Tubingen, Germany Univ Tubingen Morgenstelle 14 Tubingen Germany D-72076 , Germany
Citazione:
U. Meyer et al., "Exchange currents in nucleon electroexcitation - art. no. 035203", PHYS REV C, 6403(3), 2001, pp. 5203

Abstract

We calculate the scalar and transverse helicity amplitudes for the electromagnetic excitation of nucleon resonances as a function of the photon four-momentum transfer. The helicity amplitudes are decomposed into electromagnetic multipoles and connected to the gammaN-->N* transition form factors. The internal N and N* dynamics is described by a constituent quark model (CQM) Hamiltonian with gluon, pion, and sigma -meson exchange potentials as residual interactions. The N and N*-resonance wave functions are obtained by solving the Schrodinger equation in a harmonic oscillator basis which contains up to N = 2 excitation quanta. For the electromagnetic current we include. in addition to the one-body current, two-body exchange currents associated with the quark-quark potentials. Exchange currents provide an effective description of the cloud of q (q) over bar pairs, which together with the valence quarks are important degrees of freedom in physical hadrons. We obtain sizable contributions of the two-body exchange currents for nearly all gamma NN* amplitudes. For some observables, e.g., the C2/M1 ratio in the gammaN-->Delta (1232) transition, and the M1 transition to the N*( 1440), exchange currents provide the most important contribution.

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Documento generato il 05/04/20 alle ore 19:30:09