Two-Photon Exchange Correction in Elastic Lepton–Proton Scattering

Tomalak, Oleksandr

doi:10.1007/s00601-018-1413-8

Cited by 15 publications

(9 citation statements)

References 30 publications

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“…For data below Q 2 ¼ 1 GeV 2 , we consider the dispersive analysis from Refs. [93][94][95][96][97][98], which determines δ ¼ δ dispersive ; details are provided in Appendix B. We take the discrepancy between the default model and the dispersive analysis as an uncertainty and allow…”

Section: Radiative Corrections To Ep Scatteringmentioning

confidence: 99%

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Parametrization and applications of the low- Q2 nucleon vector form factors

et al. 2020

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We present the proton and neutron vector form factors in a convenient parametric form that is optimized for momentum transfers ≲ few GeV 2. The form factors are determined from a global fit to electron scattering data and precise charge radius measurements. A new treatment of radiative corrections is applied. This parametric representation of the form factors, uncertainties, and correlations provides an efficient means to evaluate many derived observables. We consider two classes of illustrative examples: neutrinonucleon scattering cross sections at GeV energies for neutrino oscillation experiments and nucleon structure corrections for atomic spectroscopy. The neutrino-nucleon charged current quasielastic cross section differs by 3%-5% compared to commonly used form factor models when the vector form factors are constrained by recent high-statistics electron-proton scattering data from the A1 Collaboration. Nucleon structure parameter determinations include: the magnetic and Zemach radii of the proton and neutron, ½r p M ; r n M ¼ ½0.739ð41Þð23Þ; 0.776ð53Þð28Þ fm and ½r p Z ; r n Z ¼ ½1.0227ð94Þð51Þ; −0.0445ð14Þð3Þ fm; the Friar radius of nucleons, ½ðr p F Þ 3 ; ðr n F Þ 3 ¼ ½2.246ð58Þð2Þ; 0.0093ð6Þð1Þ fm 3 ; the electric curvatures, ½hr 4 i p E ; hr 4 i n E ¼ ½1.08ð28Þð5Þ; −0.33ð24Þð3Þ fm 4 ; and bounds on the magnetic curvatures, ½hr 4 i p M ; hr 4 i n M ¼ ½−2.0ð1.7Þð0.8Þ; −2.3ð2.1Þð1.1Þ fm 4. The first and dominant uncertainty is propagated from the experimental data and radiative corrections, and the second error is due to the fitting procedure.

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Section: Radiative Corrections To Ep Scatteringmentioning

confidence: 99%

“…The intermediate region is described by interpolation between these two calculations as in Ref. [98]. We denote this dispersive result as δ dispersive and provide the corresponding correction for each point in the Mainz dataset in the Supplemental Material [100].…”

Section: Appendix B: Two-photon Exchangementioning

confidence: 99%

Parametrization and applications of the low- Q2 nucleon vector form factors

et al. 2020

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“…The two e − p event generators were found to be in excellent agreement with each other. They also included the contribution from the two-photon exchange processes [45][46][47], which were estimated to be less than 0.2% for the e − p elastic scattering cross section in the PRad kinematic range. All the generators are able to generate hard radiated photons, beyond the peaking approximation, by which the radiated photon will be co-linear with the electron.…”

Section: Improved Radiative Corrections At Forward Anglesmentioning

confidence: 99%

“…The calculations of the e − p elastic and Møller radiative corrections are performed within a covariant formalism, without the usual ultra relativistic approximation [24], where the mass of the electron is neglected. The two generators also include contributions from two-photon exchange processes [45][46][47]. A second independent e − p elastic event generator [25] was used as a cross check.…”

Section: A Comprehensive Simulationmentioning

confidence: 99%

PRad-II: A New Upgraded High Precision Measurement of the Proton Charge Radius

Gasparian¹,

H²,

Dutta³

et al. 2020

Preprint

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The PRad experiment has credibly demonstrated the advantages of the calorimetric method in e − p scattering experiments to measure the proton root-mean-square (RMS) charge radius with high accuracy. The PRad result, within its experimental uncertainties, is in agreement with the small radius measured in muonic hydrogen spectroscopy experiments and it was a critical input in the recent revision of the CODATA recommendation for the proton charge radius. Consequently, the PRad result is in direct conflict with all modern electron scattering experiments. Most importantly, it is 5.8% smaller than the value from the most precise electron scattering experiment to date, and this difference is about three standard deviations given the precision of the PRad experiment. As the first experiment of its kind, PRad did not reach the highest precision allowed by the calorimetric technique. Here we propose a new (and) upgraded experiment -PRad-II, which will reduce the overall experimental uncertainties by a factor of 3.8 compared to PRad and address this as yet unsettled controversy in subatomic physics. In addition, PRad-II will be the first lepton scattering experiment to reach the Q 2 range of 10 −5 GeV 2 allowing a more accurate and robust extraction of the proton charge radius. The muonic hydrogen result with its unprecedented precision ( 0.05%) determines the CODATA value of the proton charge radius, hence, it is critical to evaluate possible systematic uncertainties of those experiments, such as the laser frequency calibration that was raised in recent review articles. The PRad-II experiment with its projected total uncertainty of 0.43% could demonstrate whether there is any systematic difference between e − p scattering and muonic hydrogen results. PRad-II will establish a new precision frontier in electron scattering and open doors for future physics opportunities. * Contact person † Spokesperson

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“…This paper deals with the neutron form factor which is experimentally not very well known but new precision measurements of this quantity are planned or presently being performed [2,3,4,5,6,7,8,9,10,11,12,13,14]. Because there are no free neutron targets the neutron form factor is determined from electron scattering on the deuteron.…”

Section: Introductionmentioning

confidence: 99%

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2020

Sohag J. Sci

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We extract a new value b = 0.0205 ± 0.0017 fm 2 of the slope of the neutron form factor G En (q 2 ) at q 2 = 0 compatible with deuteron properties by using a linear relation between b and A 2 S (1 + η 2 ) we found for a class of nonlocal potential models having the experimental values of both r D and Q. Another model dependent value b MHKZ = 0.0206 ± 0.0014 fm 2 , which is also compatible with deuteron properties, has been determined by applying "constrained" unitary transformations to the local MHKZ potential model. The sensitivity of a small changes in the experimental values used for r D and Q on the value obtained for b is also investigated.

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Two-Photon Exchange Correction in Elastic Lepton–Proton Scattering

Cited by 15 publications

References 30 publications

Parametrization and applications of the low- Q2 nucleon vector form factors

Parametrization and applications of the low- Q2 nucleon vector form factors

PRad-II: A New Upgraded High Precision Measurement of the Proton Charge Radius

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