Pion photoproduction in the Δ resonance region

Arndt, Richard A.; Strakovsky, I. I.; Workman, R. L.

doi:10.1103/physrevc.56.577

Cited by 26 publications

(31 citation statements)

References 12 publications

(19 reference statements)

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“…(14). Separately shown are s-channel integrals from single-pion photoproduction with SAID [13] and HDT [14] multipoles, and from multi-pion production. The t-channel integral includes both the pole contributions of low-lying pseudoscalar mesons and their radial excitations (see the text).…”

Section: Discussionmentioning

confidence: 99%

“…(13). Since the 2π contribution to Im t A is forbidden and since the phase space for 3π at low energies is small, one can expect a strong dominance of γ t π by the lightest pseudoscalar meson π 0 and, to a lesser extent, by η and η ′ .…”

Section: Saturation Of the Sum Rulementioning

confidence: 98%

“…The latter are taken from the computer code SAID, solution SP97K [13], and for large angular momenta j = l ± from the one-pion-exchange diagram (Ref. [7], appendix B).…”

Section: Saturation Of the Sum Rulementioning

confidence: 99%

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Sum rule for the backward spin polarizability of the nucleon from a backward dispersion relation

L’vov

Nathan

1999

Phys. Rev. C

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A new sum rule for γ π , the backward spin polarizability of the nucleon, is derived from a backward-angle dispersion relation. Taking into account single-and multi-pion photoproduction in the s-channel up to the energy ω max = 1.5 GeV and resonances in the t-channel with mass below 1.5 GeV, it is found for the proton and neutron that [γ π ] p = −39.5 ± 2.4 and [γ π ] n = 52.5 ± 2.4, respectively, in units of 10 −4 fm 4 .

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Section: Discussionmentioning

confidence: 99%

Section: Saturation Of the Sum Rulementioning

confidence: 98%

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Sum rule for the backward spin polarizability of the nucleon from a backward dispersion relation

L’vov

Nathan

1999

Phys. Rev. C

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“…Among the reasons for that is that experiments on Compton scattering by the proton in the ∆-resonance range [229] and photoproduction experiments (like [146]) carried out at MAMI (Mainz) lead to a more precise determination of the resonant M 1+ amplitude of the ∆ photoexcitation. Now [230,231] this amplitude is by about 3% lower than it was assumed a few years ago in the SAID (SM95) parametrization of photo-meson amplitudes [232].…”

Section: Status Of the Free Polarizabilities Of The Nucleonmentioning

confidence: 94%

Compton scattering by nuclei

et al. 2000

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The concept of Compton scattering by even-even nuclei from giant-resonance to nucleon-resonance energies and the status of experimental and theoretical researches in this field are outlined. The description of Compton scattering by nuclei starts from different complementary approaches, namely from second-order S-matrix and from dispersion theories. Making use of these, it is possible to incorporate into the predicted nuclear scattering amplitudes all the information available from other channels, viz. photon-nucleon and photon-meson channels, and to efficiently make use of models of the nucleon, the nucleus and the nucleon-nucleon interaction. The total photoabsorption cross section constrains the nuclear scattering amplitude in the forward direction. The specific information obtained from Compton scattering therefore stems from the angular dependence of the nuclear scattering amplitude, providing detailed insight into the dynamics of the nuclear and nucleon degrees of freedom and into the interplay between them. Nuclear Compton scattering in the giant-resonance energy-region provides information on the dynamical properties of the in-medium mass of the nucleon. Most prominently, the electromagnetic polarizabilities of the nucleon in the nuclear medium can be extracted from nuclear Compton scattering data obtained in the quasideuteron energy-region. In our description of this latter process special emphasis is laid upon the exploration of many-body and two-body effects entering into the nuclear dynamics. Recent results are presented for two-body effects due to the mesonic seagull amplitude and due to the excitation of nucleon internal degrees of freedom accompanied by meson exchanges. Due to these studies the inmedium electromagnetic polarizabilities are by now well understood, whereas the understanding of nuclear Compton scattering in the ∆-resonance range is only at the beginning. Furthermore, phenomenological methods how to include retardation effects in the scattering amplitude are discussed and compared with model predictions.

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“…In our actual calculations, both the πN phase shifts δ (α) and inelasticity parameters η α are taken from the analysis of the GWU group [10].…”

Section: Photo-and Electroproductionmentioning

confidence: 99%

Electroproduction of nucleon resonances

Tiator¹,

Drechsel²,

Kamalov³

et al. 2004

Perspectives in Hadronic Physics

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Abstract. The unitary isobar model MAID has been extended and used for a partial wave analysis of pion photo-and electroproduction in the resonance region W < 2 GeV. Older data from the world data base and more recent experimental results from Mainz, Bates, Bonn and JLab for Q 2 up to 4.0 (GeV/c) 2 have been analyzed and the Q 2 dependence of the helicity amplitudes have been extracted for a series of four star resonances. We compare single-Q 2 analyses with a superglobal fit in a new parametrization of Maid2003 together with predictions of the hypercentral constituent quark model. As a result we find that the helicity amplitudes and transition form factors of constituent quark models should be compared with the analysis of bare resonances, where the pion cloud contributions have been subtracted.

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Pion photoproduction in the Δ resonance region

Cited by 26 publications

References 12 publications

Sum rule for the backward spin polarizability of the nucleon from a backward dispersion relation

Sum rule for the backward spin polarizability of the nucleon from a backward dispersion relation

Compton scattering by nuclei

Electroproduction of nucleon resonances

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