Helicity dependence of the γ→p→→nπ+π0 reaction in the second resonance region

Ahrens, J.; Altieri, S.; Annand, J. R. M.; Anton, G.; Arends, H. J.; Aulenbacher, K.; Beck, R.; Bradtke, C.; Braghieri, A.; Degrande, N.; d’Hose, N.; Dutz, H.; Goertz, Stefan; Grabmayr, P.; Hansen, Kurt Schaldemose; Harmsen, J.; Harrach, D. von; Hasegawa, S.; Hasegawa, T.; Heid, E.; Helbing, K.; Holvoet, H.; Hoorebeke, Luc Van; Horikawa, N.; Iwata, T.; Jahn, O.; Jennewein, P.; Kageya, T.; Kiel, B.; Klein, Frank; Kondratiev, R.; Kossert, Karsten; Krimmer, J.; Lang, Μ.; Lannoy, B.; Leukel, R.; Lisin, V.; Matsuda, T.; McGeorge, J. C.; Meier, A.; Menze, D.; Meyer, W.; Michel, Thilo; Naumann, J.; Panzeri, A.; Pedroni, P.; Pinelli, T.; Preobrajenski, I.; Radtke, Edgar; Reichert, E.; Reicherz, G.; Rohlof, Ch.; Rosner, G.; Rostomyan, T.; Rovelli, C.; Ryckbosch, D.; Sauer, Michelle; Schoch, B.; Schumacher, M.; Seitz, B.; Speckner, T.; Takabayashi, N.; Tamas, G.; Thomas, A.; Vyver, R. Van de; Wakai, A.; Weihofen, W.; Wissmann, F.; Zapadtka, F.; Zeitler, G.

doi:10.1016/s0370-2693(02)03008-3

Cited by 58 publications

(36 citation statements)

References 21 publications

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“…As shown in Table III, this procedure yields a multi-pion contribution of (20 ± 2) µb to the GDH sum rule. On the other hand, we have evaluated this contribution on the basis of recently published data for the helicity dependence of the γp → Nππ channels in the energy range 325 MeV < E γ < 800 MeV [37][38][39].…”

Section: B Discussion Of the Resultsmentioning

confidence: 99%

Higher order forward spin polarizability

2010

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As a guideline for future experiments to extract the four (leading) spin polarizabilities of the nucleon, we have constructed the forward amplitude for polarized Compton scattering by dispersion integrals. These integrals have been saturated by recently measured helicity-dependent photoabsorption cross sections as well as predictions for pion photoproduction multipoles from several phenomenological descriptions and chiral perturbation theory. The comparison of these results corroborates the strategy to extract the spin polarizabilities by fitting them to polarizedCompton data and fixing all higher order spin effects by dispersion relations based on pion photoproduction multipoles.

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Section: B Discussion Of the Resultsmentioning

confidence: 99%

Higher order forward spin polarizability

2010

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“…Nonetheless, a more demanding test to the model can be done by evaluating polarization observables, since it can be sensible to details of the model not visible when integrating over polarization degrees of freedom in the unpolarized observables. In this line, a test of the model of [15] was done in [22] when evaluating the spin 1/2 and 3/2 amplitudes and the contribution to the GDH sum rule of the double pion channel, in fair agreement with Mainz results [23,24], and the evaluation of beam asymmetries under experimental study at GRAAL [5]. These observables are based on differences of total differential cross sections dependent on polarization, which provide a valuable information on the internal dynamics of the reaction.…”

Section: Introductionmentioning

confidence: 87%

Helicity asymmetries in double pion photoproduction on the proton

Roca¹

2005

Nuclear Physics A

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Based on a prior model on double pion photoproduction on the proton, successfully tested in total cross sections and invariant mass distributions, we make a theoretical study of the angular dependence of helicity asymmetries from the interaction of circularly polarized photons with unpolarized protons. We show that this observable is sensitive to details of the internal mechanisms and, thus, represents a complementary test of the theoretical model.

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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%

“…This is experimental proof that twopion production can not be simply explained by a resonance driven mechanism (s-channel contribution), but that it requires large non-resonant effects such as Born terms and vector meson exchange in the t-channel. The channels nπ + π 0 , pπ + π − , and pπ 0 π 0 were separately analyzed in the MAMI experiment [67]. As an example we show the cross section for γ p → nπ + π 0 in Figure 6.…”

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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Helicity dependence of the γ→p→→nπ+π0 reaction in the second resonance region

Cited by 58 publications

References 21 publications

Higher order forward spin polarizability

Higher order forward spin polarizability

Helicity asymmetries in double pion photoproduction on the proton

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

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