Compton scattering by the proton through θcms = 75° and 90° in the Δ-resonance region

Hünger, A.; Peise, J.; Robbiano, A.; Ahrens, J.; Anthony, I.; Arends, H. J.; Beck, R.; Capitani, G. P.; Dolbilkin, B.S.; Falkenberg, H.; Galler, G.; Hall, S.J.; Kellie, J. D.; Kondratjev, R.; Kordsmeier, R.; Lisin, V.; L’vov, A. I.; Miller, G.J.; Molinari, C.; Ottonello, P.; Reolon, A. R.; Sanzone, M.; Schmitz, M.; Schneider, M.; Schumacher, M.; Selke, O.; Walcher, Th.; Wissmann, F.; Wolf, S.; Zucchiatti, A.

doi:10.1016/s0375-9474(97)00184-x

Cited by 29 publications

(42 citation statements)

References 68 publications

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“…(2) for photon energies up to 1 GeV. The cross section in the ∆-resonance region agrees with the data as well as with other calculations which are based on dispersion relations [31,33,34], and an effective Lagrangian [35]. For comparison we show results of the calculations from Ref.…”

Section: Description Of the Model And Comparison With Data For Reasupporting

confidence: 84%

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Photoproduction of electron–positron pairs on the proton in the resonance region

Korchin¹,

Scholten²

2001

Nuclear Physics A

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Production of lepton pairs in the γp → e − e + p reaction is studied at photon energies up to 1 GeV. We show that even if lepton charge is not measured there are extensive kinematical regimes where the nuclear process dominates over the Bethe-Heitler contribution. The decomposition is performed of the unpolarized cross section for the virtual Compton scattering in terms of response functions. These are expressed in terms of a polarization density matrix of the virtual photon and are shown to be sensitive to the properties of baryon resonances in the first and the second resonance regions. In the analysis a unitary K-matrix model is used, based on an effective Lagrangian including nucleon, mesons, and baryon resonances with masses up to 1.7 GeV. Results of the model are compared with data for real-photon Compton scattering and predictions are given for observables in photoproduction of lepton pairs.

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Section: Description Of the Model And Comparison With Data For Reasupporting

confidence: 84%

“…This effect comes as a result of a balance between G 1 (k 2 ) and G 2 (k 2 ) contributions in the γN∆ vertex in Eq. (33). Note also that in the quark model in Table II the electric quadrupole is absent, E2 = L2 = 0, which corresponds to a particular choice of the couplings 2mg…”

Section: B Results For Response Functions In Virtual Compton Scatteringmentioning

confidence: 98%

Photoproduction of electron–positron pairs on the proton in the resonance region

Korchin¹,

Scholten²

2001

Nuclear Physics A

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“…A similar cusp structure is also seen in the analysis of Ref. [4]. Extending our model with other degrees of freedom will add a smooth function to f 1− EE , changing the value at the higher energies but should not affect the cusp structure.…”

Section: Application In Compton Scatteringsupporting

confidence: 80%

Compton scattering in a unitary approach with causality constraints

Kondratyuk

Scholten

2000

Nuclear Physics A

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Pion-loop corrections for Compton scattering are calculated in a novel approach based on the use of dispersion relations in a formalism obeying unitarity. The basic framework is presented, including an application to Compton scattering. In the approach the effects of the non-pole contribution arising from pion dressing are expressed in terms of (half-off-shell) form factors and the nucleon self-energy. These quantities are constructed through the application of dispersion integrals to the pole contribution of loop diagrams, the same as those included in the calculation of the amplitudes through a K-matrix formalism. The prescription of minimal substitution is used to restore gauge invariance. The resulting relativistic-covariant model combines constraints from unitarity, causality, and crossing symmetry.

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“…Meanwhile, some additional work has been carried out which has to be discussed here. Experiments on Compton scattering by the proton in the ∆ resonance range carried out at MAMI (Mainz) and other data led to the conclusion [21] that the M 1+ amplitude of the SAID(SM95) parametrization of photo meson amplitudes [22] had to be reduced by about 2.8%. This finding initiated a re-evaluation of the parametrization of photo-meson amplitudes now available as SAID(SP97K) which to a large extent confirmed the findings of [21].…”

Section: Status Of the Free Polarizabilities Of The Nucleonmentioning

confidence: 99%

“…Experiments on Compton scattering by the proton in the ∆ resonance range carried out at MAMI (Mainz) and other data led to the conclusion [21] that the M 1+ amplitude of the SAID(SM95) parametrization of photo meson amplitudes [22] had to be reduced by about 2.8%. This finding initiated a re-evaluation of the parametrization of photo-meson amplitudes now available as SAID(SP97K) which to a large extent confirmed the findings of [21]. On the basis of this new parametrization, SAID(SP97K), Babusci et al [5] carried out a new evaluation of the Baldin-Lapidus sum rule and obtainedᾱ p +β p = 13.69 ± 0.14 (in units of 10 −4 f m 3 ) instead of the previous α p +β p = 14.2 ± 0.3 for the proton andᾱ n +β n = 14.40 ± 0.66 instead of the previousᾱ n +β n = 15.8 ± 0.5 for the neutron.…”

Section: Status Of the Free Polarizabilities Of The Nucleonmentioning

confidence: 99%