Two-photon exchange from intermediate state resonances in elastic electron-proton scattering

Abstract

We calculate the beam (B n ) and target (A n ) normal single-spin asymmetries in electron-proton elastic scattering from two-photon exchange amplitudes with resonance intermediate states of spinparity 1/2 ± and 3/2 ± and mass W ≲ 1.8 GeV. The latest CLAS exclusive meson electroproduction data are used as input for the transition amplitudes from the proton to the excited resonance states.For B n , the spin 3/2 resonances dominate by an order of magnitude over the spin 1/2 states. In general we observe cancellations between the negative contributions of the ∆(1232) and N (1520) across both beam energy and scattering angle, and the positive contributions of the ∆(1700) and N (1720), leading to a rather large overall uncertainty band in the total B n . At forward angles and beam energies E lab < 1 GeV, where the ∆(1232) dominates, the calculated B n tend to overshoot the A4 and SAMPLE data. The calculated B n compare well with the measured values from the A4 and Q weak experiments with E lab > 1 GeV.

Dispersion-theoretical analysis of the electromagnetic form factors of the nucleon: Past, present and future

“…[117,118] for reviews and very recent work in Ref. [119]. Here, we concentrate on the work presented in [46], because the two-photon corrections given there are applied in the DR analyses since then.…”

Reliability Analysis of the Results of the Known Experiments on Measuring of the Sachs Form Factor Ratio Using the Rosenbluth Technique. Polarization of the Final Proton in the $e \vec p \to e \vec p$ Elastic Process

“…The accuracy of Rosenbluth cross section measurements ∆ 0 appearing in ( 22) and ( 23) is determined in the general case by statistical, systematic, and normalization uncertainties. Below in the reliability analysis of the experimental measurements [8], it will be established on the basis of the results [43] that ∆ 0 is determined by the normalization uncertainty. Note that the limits on the kinematics of the experiment conducted using RT was not considered in the literature, including [42,43,49,50].…”

“…Below in the reliability analysis of the experimental measurements [8], it will be established on the basis of the results [43] that ∆ 0 is determined by the normalization uncertainty. Note that the limits on the kinematics of the experiment conducted using RT was not considered in the literature, including [42,43,49,50]. Nevertheless, it seems to be an important issue that deserves attention.…”

“…In [43], three well-known experiments [7][8][9] were reanalyzed in the region of Q 2 5 GeV 2 using the RT, the improved RC calculation procedures from [42], and the TPE contribution calculated by the authors of [43]. Though they were the precision experiments, and one of them [9] even got a special name (Super-Rosenbluth), the discrepancies between the measurements by the RT and by the polarization method could be eliminated only for experiment [8] and only in the region of Q 2 < 5 GeV 2 .…”

“…The goal of this work is to try to find out why the results of the experiments [7][8][9] failed to be reconciled in [43] with the results [17] and what can come out of a similar [43] reanalysis of the experimental results [41]. To this end, a criterion for assessing the reliability of RT measurements of the ratio R is proposed and used to analyze the experimental measurements [7][8][9]41].…”