<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>π</mml:mi><mml:mi>NN</mml:mi></mml:math>coupling and two-pion photoproduction on the nucleon

Hirata, Michihiro; Katagiri, Nobuhiko; Takaki, T.

doi:10.1103/physrevc.67.034601

Cited by 54 publications

(81 citation statements)

References 23 publications

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“…Namely, the negative q 2 -dependent contribution to the s-wave amplitude in [2] requires on the other hand a much stronger momentum independent part at low energy than in our model, thus making the energy dependence of the cross section less pronounced. Here we do not discuss such effects like π + π − → π 0 π 0 scattering, considered in [29] at very low energies, as well as the influence of the type of πN N coupling, discussed in [30]. In any case, because of such a strong model dependence of the low energy π 0 π 0 cross section, more refined theoretical and experimental investigations of this channel are needed.…”

Section: The γN → ππN Modelmentioning

confidence: 99%

Double-pion photoproduction on nucleon and deuteron

2005

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Photoproduction of two pions on nucleon and deuteron is studied for photon energies from threshold up to Eγ = 1.5 GeV. For the elementary operator an effective Lagrangean approach is used with resonance and Born contributions. The model parameters are fixed by resonance decay widths and multipole analyses of single pion photoproduction. A satisfactory description of total cross sections of two-pion production on the proton for various charge channels is achieved, except for π 0 π 0 production for which a significant underestimation is found near threshold. The operator then serves for the evaluation of this reaction on the deuteron in the impulse approximation. In addition, N N rescattering in the final state is taken into account, but πN and ππ rescatterings are neglected. Results are presented for total cross sections and target asymmetries.PACS numbers: 13.60.-r, 13.60. Le, 21.45.+v,

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Section: The γN → ππN Modelmentioning

confidence: 99%

Double-pion photoproduction on nucleon and deuteron

2005

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“…The theoretical predictions are shown by the solid lines [55], dashed lines [68], and dotted lines [69]. The data are from MAMI [67].…”

Section: Figmentioning

confidence: 99%

The Gerasimov-Drell-Hearn Sum Rule and the Spin Structure of the Nucleon

Drechsel

Tiator

2004

Annu. Rev. Nucl. Part. Sci.

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The Gerasimov-Drell-Hearn sum rule is one of several dispersive sum rules that connect the Compton scattering amplitudes to the inclusive photoproduction cross sections of the target under investigation. Being based on such universal principles as causality, unitarity, and gauge invariance, these sum rules provide a unique testing ground to study the internal degrees of freedom that hold the system together. The present article reviews these sum rules for the spin-dependent cross sections of the nucleon by presenting an overview of recent experiments and theoretical approaches. The generalization from real to virtual photons provides a microscope of variable resolution: At small virtuality of the photon, the data sample information about the long range phenomena, which are described by effective degrees of freedom (Goldstone bosons and collective resonances), whereas the primary degrees of freedom (quarks and gluons) become visible at the larger virtualities. Through a rich body of new data and several theoretical developments, a unified picture of virtual Compton scattering emerges, which ranges from coherent to incoherent processes, and from the generalized spin polarizabilities on the low-energy side to higher twist effects in deep inelastic lepton scattering.

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“…Several models have been developed for analyzing the double pion photoproduction [40,41,42,43,44] and electroproduction [45] reactions in the nucleon resonance excitation region, beginning with the pioneering effort of [39]. They are based on the tree-diagrams of effective meson-baryon Lagrangians and have been reasonably successful in describing the very limited data of the fully integrated cross sections and the invariant mass distributions.…”

Section: Introductionmentioning

confidence: 99%