Analysis of approximations used in calculations of radiative corrections to electron-proton scattering cross section

Gerasimov, R. E.; Fadin, V. S.

doi:10.1134/s1063778815010081

Cited by 12 publications

(14 citation statements)

References 32 publications

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“…At this point, it is worth mentioning that ∆ is the upper limit of the integration over the photon energy in Eq. (25). This quantity is chosen to be smaller than any of the other energies of an experiment and serves as a parameter that splits the photon's phase space into the soft and hard regions.…”

Section: Fig 3 Proton Leg Bremsstrahlung Diagrammentioning

confidence: 99%

“…As a result, in the presence of experimental cuts, the upper integration limit in Eq. (25) has to be chosen based on the following condition ν = Min (ν cut , ν max ).…”

Section: Fig 3 Proton Leg Bremsstrahlung Diagrammentioning

confidence: 99%

“…In particular, they calculated exactly the bremsstrahlung interference contribution, whereas the corresponding calculation of Tsai is approximate; for the detailed discussion on the difference between the two approaches, please see Ref. [25]. Despite many advantages of the work of Maximon and Tjon, we believe that the work of Tsai is more selfconsistent in its definition of soft photons.…”

Section: Introductionmentioning

confidence: 99%

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Charge asymmetry in elastic scattering of massive leptons on protons

Koshchii¹,

Afanasev²

2017

Phys. Rev. D

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The charge asymmetry due to higher-order QED corrections in elastic lepton-proton scattering is estimated without employing the ultrarelativistic approximation. Our calculation is performed by generalizing the soft-photon approximation approach suggested by Tsai. Corresponding loop integrals that take a form of Passarino-Veltman scalar three-point functions are calculated analytically without neglecting the mass of the lepton. Our results provide model-independent charge asymmetry predictions for scattering of unpolarized and massive leptons on proton targets. These predictions can be used in corresponding experiments to determine the contribution coming from model-dependent hard two-photon exchange processes.

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Section: Fig 3 Proton Leg Bremsstrahlung Diagrammentioning

confidence: 99%

“…As a result, in the presence of experimental cuts, the upper integration limit in Eq. (25) has to be chosen based on the following condition ν = Min (ν cut , ν max ).…”

Section: Fig 3 Proton Leg Bremsstrahlung Diagrammentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Charge asymmetry in elastic scattering of massive leptons on protons

Koshchii¹,

Afanasev²

2017

Phys. Rev. D

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“…[21,22]. New results on radiative corrections based on the lepton structure functions method, that takes into account higher orders in the leading logarithm approximation [23], can bring FF results in agreement [24].…”

Section: Pacs Numbersmentioning

confidence: 64%

Form factor ratio from unpolarized elastic electron-proton scattering

Pacetti

Tomasi–Gustafsson

2016

Phys. Rev. C

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A reanalysis of unpolarized electron-proton elastic scattering data is done in terms of the electric to magnetic form factor squared ratio. This observable is in principle more robust against experimental correlations and global normalizations. The present analysis shows indeed that it is a useful quantity that contains reliable and coherent information. The comparison with the ratio extracted from the measurement of the longitudinal to transverse polarization of the recoil proton in polarized electronproton scattering shows that the results are compatible within the experimental errors. Limits are set on the kinematics where the physical information on the form factors can be safely extracted. The results presented in this work bring a decisive piece of information to the controversy on the deviation of the proton form factors from the dipole dependence. PACS numbers:Hadron form factors (FFs) contain essential information on the electric and magnetic charge currents in the hadron and constitute a very convenient parametrization that enters in theoretical models and description of experimental observables concerning the three-leg vertex proton-proton-photon. It has been assumed for long time that the proton electric FF, as well as the magnetic FFs of the proton and neutron, normalized to their magnetic moment, have a Q 2 -dipole dependence (Q is the four momentum of the photon):, whereas the neutron electric FF is essentially zero. Evidence for the deviation of the proton electric FF from the dipole form was present since the 70's, in experiments as well as in theory. However, the dipole parametrization was commonly accepted due to the following facts:• From the classical point of view, in the nonrelativistic approximation, FFs are Fourier transforms of the spatial densities of electric charge and magnetization of the nucleon; the dipole approximation corresponds to an exponential distribution and the parameter 0.71 GeV 2 corresponds to a quite reasonable root mean square radius of the proton of 0.81 fm.• From the QCD point of view, as elastic FFs represent the probability that a proton remains in its ground state after that each of its valence quarks has received a momentum squared, Q 2 , transferred by the virtual photon, scaling laws predict a (1/Q 2 ) 2 dependence of the amplitude of the process [1, 2] (corresponding to two gluon exchange, the minimum number of exchanges needed for sharing the momentum among the three valence quarks). * Electronic address: etomasi@cea.frThe reduced cross section of electron-proton elastic scattering, in Born approximation, i.e., by considering only one-photon exchange, σ red , is linear in the variable ǫ = [1 + 2(1 + τ ) tan 2 (θ e /2)] −1 , being θ e the electron scattering angle in the proton rest frame, and τ = Q 2 /(4M 2 ), and it readswhere M is the proton mass, E and dσ/dΩ are the electron initial energy and the differential cross section in the proton rest frame, and G E and G M are the proton electric and magnetic Sachs FFs. The measurement of the differential (reduc...

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“…A Q 2 -increasing discrepancy appeared between polarized and unpolarized elastic scattering experiments, giving rise to a large number of publications and speculations. Several issues were discussed: radiative corrections [6][7][8], parameter correlations [9], relative normalization within a set of data and among sets of data [10,11], as well as the validity of the one-photon exchange approximation. This last point is of main interest for the present work.…”

Section: Introductionmentioning

confidence: 99%

Updated analysis of recent results on electron and positron elastic scattering on the proton

Tomasi–Gustafsson

2019

Phys. Rev. C

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We discuss recent experimental results concerning the cross section ratio of positron over electron elastic scattering on protons, and compare with the predictions of a pre-existent calculation. The deviation from unity of this ratio, i.e., a charge asymmetry different from zero, is the signature of contributions beyond the Born approximation. After reviewing the published results, we compare the elastic data to a calculation which includes the diagram corresponding to two-photon exchange.It turns out that all the data on the cross section ratio, in the limit of their precision, do not show evidence of enhanced two-photon contribution beyond the expected percent level. Our results confirm that experimental evidence for a large contribution of two-photon exchange is not yet found.

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Analysis of approximations used in calculations of radiative corrections to electron-proton scattering cross section

Cited by 12 publications

References 32 publications

Charge asymmetry in elastic scattering of massive leptons on protons

Charge asymmetry in elastic scattering of massive leptons on protons

Form factor ratio from unpolarized elastic electron-proton scattering

Updated analysis of recent results on electron and positron elastic scattering on the proton

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