Improved radiative corrections for (e, e'p) experiments: Beyond the peaking approximation and implications of the soft-photon approximation

Weissbach, Florian; Hencken, Kai; Rohe, D.; Sick, I.; Trautmann, D.

doi:10.1140/epja/i2005-10319-4

Cited by 5 publications

(25 citation statements)

References 29 publications

(71 reference statements)

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“…A similar reexamination of the MoTsai procedure was made by Vanderhaeghen et al [Vdh00] in the process of a detailed calculation of radiative corrections for virtual Compton (VCS). Also recently Ent et al [Ent01] and Weissbach et al [Wei04] have published improvements and detailed studies of the radiative correction calculation technique for coincidence experiments (e,e'p).…”

Section: Rosenbluth Results and Radiative Correctionsmentioning

confidence: 99%

Nucleon electromagnetic form factors

Perdrisat

Punjabi

Vanderhaeghen

2007

Progress in Particle and Nuclear Physics

474

583

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There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at MIT-Bates, MAMI, and JLab. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.

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Section: Rosenbluth Results and Radiative Correctionsmentioning

confidence: 99%

Nucleon electromagnetic form factors

Perdrisat

Punjabi

Vanderhaeghen

2007

Progress in Particle and Nuclear Physics

474

583

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“…The sum of the radiated photon energy thus has a fairly realistic angular distribution, as shown in Ref. [36,81].…”

Section: F Radiative Correctionsmentioning

confidence: 90%

Measurement of two-photon exchange effect by comparing elastic e±p cross sections

Rimal¹,

Adikaram²,

Raue³

et al. 2017

Phys. Rev. C

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Measurement of two-photon exchange effect by comparing elastic e ± p cross sections Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four momentum transfer (Q 2 ). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed. Purpose:We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections in order to determine the TPE contribution to elastic electron-proton scattering and thereby resolve the proton electric form factor discrepancy.Methods: We produced a mixed simultaneous electron-positron beam in Jefferson Lab's Hall B by passing the 5.6 GeV primary electron beam through a radiator to produce a bremsstrahlung photon beam and then passing the photon beam through a convertor to produce electron/positron pairs. The mixed electron-positron (lepton) beam with useful energies from approximately 0.85 to 3.5 GeV then struck a 30-cm long liquid hydrogen (LH2) target located within the CEBAF Large Acceptance Spectrometer (CLAS). By detecting both the scattered leptons and the recoiling protons we identified and reconstructed elastic scattering events and determined the incident lepton energy. A detailed description of the experiment is presented.Results: We present previously unpublished results for the quantity R2γ, the TPE correction to the elasticscattering cross section, at Q 2 ≈ 0.85 and 1.45 GeV 2 over a large range of virtual photon polarization ε. Conclusions:Our results, along with recently published results from VEPP-3, demonstrate a non-zero contribution from TPE effects and are in excellent agreement with the calculations that include TPE effects and largely reconcile the form-factor discrepancy up to Q 2 ≈ 2 GeV 2 . These data are consistent with an increase in R2γ with decreasing ε at Q 2 ≈ 0.85 and 1.45 GeV 2 . There are indications of a slight increase in R2γ with Q 2 .

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“…The peaking approximation can be removed from (e, e p) data analyses, as has been shown in Ref. [10]. Now we consider the SPA cross section for multiphoton bremsstrahlung with total photon energy below the low-energy cutoff E 0 together with the emission of n photons with energies above the cutoff, which is given as [8] …”

Section: Multiphoton Spa Cross Sectionmentioning

confidence: 99%

“…This acceptance function allows to get not only the total, but also the differential cross section, or ones where the detection of some of the particles is only in some kinematical range, by selections different functions for χ n A . We obtain then the photon-integrated cross section [10] as…”

Section: Multiphoton Spa Cross Sectionmentioning

confidence: 99%

“…Strictly speaking the SPA is only valid in the limit where all bremsstrahlung photon energies go to zero. In data analyses the approximation is applied however to emission of bremsstrahlung photons with finite energies [10]. The question arises up to which upper bound for the maximum bremsstrahlung photon energy the SPA is a good approximation.…”

Section: Introductionmentioning

confidence: 99%

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Improved radiative corrections to(e,e'p)experiments: Explicit treatment of kinematical corrections in multiphoton bremsstrahlung

et al. 2009

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Radiative processes lead to important corrections to (e, e p) experiments. While radiative corrections can be calculated exactly in QED and to a good accuracy also including hadronic corrections, these corrections cannot be included into data analyses to arbitrary orders exactly. Nevertheless consideration of multiphoton bremsstrahlung above the low-energy cutoff is important for many (e, e p) experiments. To date, higher-order bremsstrahlung effects concerning electron scattering experiments have been implemented approximately by employing the soft-photon approximation (SPA). In this paper we propose a novel approach to multiphoton emission which partially removes the SPA from (e, e p) experiments. In this combined approach one hard photon is treated exactly; and additional (softer) bremsstrahlung photons are taken into account resorting to the soft-photon approximation. This partial removal of the soft-photon approximation is shown to be relevant for the missing-energy distribution for several kinematic settings at MAMI and TJNAF energies.

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Improved radiative corrections for (e, e'p) experiments: Beyond the peaking approximation and implications of the soft-photon approximation

Cited by 5 publications

References 29 publications

Nucleon electromagnetic form factors

Nucleon electromagnetic form factors

Measurement of two-photon exchange effect by comparing elastic e±p cross sections

Improved radiative corrections to(e,e'p)experiments: Explicit treatment of kinematical corrections in multiphoton bremsstrahlung

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