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Harari, Haim; Horn, D.; Kügler, M.; Lipkin, Harry J.; Meshkov, S.

doi:10.1103/physrev.140.b431

Cited by 9 publications

(1 citation statement)

References 20 publications

(23 reference statements)

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“…where µ(γp → ∆) is related to the γN → ∆(1232)P 33 magnetic-dipole form factor as [194]: Another prediction, which is a direct result of this assumption, is that the electric-quadrupole and scalar quadrupole γN → ∆(1232)P 33 transitions are forbidden [195,196]:…”

Section: Cqm and Pion-cloud Contributionmentioning

confidence: 99%

Electroexcitation of nucleon resonances

Aznauryan,

Burkert

2011

Preprint

107

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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 π and η electroproduction off protons, and theoretical approaches used for the extraction of resonance contributions from the experimental data. The status of 2π, KΛ, and KΣ 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 Q 2 up to 8 and 4.5 GeV 2 for the ∆(1232)P 33 , N (1535)S 11 and N (1440)P 11 , N (1520)D 13 , respectively. These results have been confronted with calculations based on lattice QCD, large-N c relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the ∆(1232) indicate large pion-cloud contributions at low Q 2 and don't show any sign of approaching the pQCD regime for Q 2 < 7 GeV 2 . Measured for the first time, the electroexcitation amplitudes of the Roper resonance, N (1440)P 11 , provide strong evidence for this state as a predominantly radial excitation of a three-quark (3q) ground state, with additional non-3-quark contributions needed to describe the low Q 2 behavior of the amplitudes. The longitudinal transition amplitude for the N (1535)S 11 was determined and has become a challenge for quark models. Explanations may require large mesoncloud contributions or alternative representations of this state. The N (1520)D 13 clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q 2 > 0.5 GeV 2 , 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.

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Section: Cqm and Pion-cloud Contributionmentioning

confidence: 99%

Electroexcitation of nucleon resonances

Aznauryan,

Burkert

2011

Preprint

107

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Decays of Positive-Parity Baryon Resonances in a BrokenŨ(12)

et al. 1965

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The simplest representations of SU(6) and Z7(12) which are capable of describing the low-lying positiveparity baryon resonances are the three-quark representations. All particle states in these multiplets are eigenstates of W spin and SU(6)w, the subgroup of Z/(12) and U(6)XU(6) which remains invariant for two-body decay processes, even when kinetic-energy terms and derivative couplings are included in the calculations. It is shown that SU(6)w leads to various selection rules and to definite branching ratios for the decays of these resonances. The branching ratios for the decays of the spin - §, SU(3)-octet resonances in the 70 representation of SU(6) and SU(6)w are calculated. An attempt is made to include SU(3) symmetrybreaking effects in a calculation of the decay rates of the | + decuple t within the 56 of SU(6)w-

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Experimental Tests of BrokenŨ(12)and ApproximateU(6)×

Harari

Lipkin

1965

Phys. Rev.

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Meson and Baryon Resonances in RelativisticSU(6)

Cited by 9 publications

References 20 publications

Electroexcitation of nucleon resonances

Electroexcitation of nucleon resonances

Decays of Positive-Parity Baryon Resonances in a BrokenŨ(12)

Experimental Tests of BrokenŨ(12)and ApproximateU(6)×

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