Suppression of hard two-photon-exchange contributions to 
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 elastic scattering cross-section ratios: A phenomenological approach

Qattan, I. A.; Patole, Shashikant P.; Alsaad, Ahmad

doi:10.1103/physrevc.101.055202

Cited by 6 publications

(4 citation statements)

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“…Corrections due to two-photon exchange (TPE) Feynman diagrams for electron scattering have received considerable interest in recent years [1][2][3][4][5][6][7][8][9][10][11][12], primarily in the context of the discrepancy of the experimental results [13,14] for the electric-to-magnetic form factor ratio, which sometimes is referred to as the proton form factor puzzle. There are strong indications [15] that this puzzle can be resolved by a proper inclusion of TPE in the experimental analysis.…”

Section: Introductionmentioning

confidence: 99%

“…When compared with the corresponding scattering data from Jefferson Lab [34] and MAMI [37,38], the second approach has been quite successful for light and intermediate-mass nuclei, e.g. 4 He, 12 C, 28 Si, and 90 Zr, while a stark disagreement between theory and experiment for BNSSA on the 208 Pb target arXiv:2102.11809v1 [nucl-th] 23 Feb 2021 2 [34], sometimes called the "PREX puzzle", was observed. This disagreement indicates that the theoretical calculation of Ref.…”

Section: Introductionmentioning

confidence: 99%

“…5.BNSSA versus momentum transfer squared |t| in the kinematical range where measurements are available. Left panel: Predictions for4 He obtained with E b = 2.750 GeV and for12 C and208 Pb with E b = 1.063 GeV. Experimental data points are from the PREX-I and HAPPEX experiments[34].…”

mentioning

confidence: 99%

“…. BNSSA for elastic electron scattering from12 C (solid blue curve),28 Si (dashed orange curve),40 Ca (solid green curve), 90 Zr (dashed-dotted black curve), and 208 Pb (solid red curve) versus momentum transfer squared |t| at E b = 953 MeV for the case when only elastic intermediate-state contributions are taken into account. For the distribution of the nuclear charge, ρ ch (r), we use an experimental fit of the world data on elastic electron-nucleus scattering parametrized in the form of a sum of Gaussians ( 12 C,28 Si,40 Ca, 208 Pb) or Fourier-Bessel ( 90 Zr) as reported in Ref [46]…”

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confidence: 99%

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Beam-normal single-spin asymmetry in elastic scattering of electrons from a spin-0 nucleus

2021

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We study the beam-normal single-spin asymmetry (BNSSA) in high-energy elastic electron scattering from several spin-0 nuclei. Existing theoretical approaches work in the plane-wave formalism and predict the BNSSA to scale as ∼ A/Z with the atomic number Z and nuclear mass number A. While this prediction holds for light and intermediate nuclei, a striking disagreement in both the sign and the magnitude of BNSSA was observed by the PREX collaboration for 208 Pb, coined the "PREX puzzle". To shed light on this disagreement, we go beyond the plane-wave approach which neglects Coulomb distortions known to be significant for heavy nuclei. We explicitly investigate the dependence of BNSSA on A and Z by i) including inelastic intermediate states' contributions into the Coulomb problem in the form of an optical potential, ii) by accounting for the experimental information on the A-dependence of the Compton slope parameter, and iii) giving a thorough account of the uncertainties of the calculation. Despite of these improvements, the PREX puzzle remains unexplained. We discuss further strategies to resolve this riddle.

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