Two photon exchange with nuclei from $$e^+/e^-$$ e + / e - elastic cross section ratios
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10050_2022_Article_682.pdf
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Author(s)
Kutz, T.
Schmidt, A.
Date Issued
February 28, 2022
Publisher
Springer Berlin Heidelberg
Citation
The European Physical Journal A. 2022 Feb 28;58(3):36
Version
Final published version
Abstract
Abstract
Hadronic box diagrams pose a significant source of radiative corrections to lepton scattering and
$$\beta $$
β
-decay measurements, yet their calculation remains highly model-dependent. Two-photon exchange is a box diagram generally relevant to most lepton scattering experiments, and is directly detectable via multiple observables. Single-spin asymmetries (SSA) are sensitive to the imaginary part of the TPE amplitude, while the ratio of
$$e^+/e^-$$
e
+
/
e
-
elastic scattering cross sections is sensitive to the real part of the TPE amplitude. While SSA measurements have been reported for several complex nuclei, measurements of the
$$e^+/e^-$$
e
+
/
e
-
ratio exist only for the proton. Proposed here is a measurement of the
$$e^+/e^-$$
e
+
/
e
-
ratio on
$$^4$$
4
He, a feasible nuclear target for which the ratio’s deviation from unity due to TPE is expected to be on order of 1–2%. Choosing a low Z nucleus minimizes Coulomb distortions, which could greatly overwhelm TPE for heavier nuclei. The proposed 19-day program, including measurements at three kinematic settings between
$$0.3< Q^2 < 0.4$$
0.3
<
Q
2
<
0.4
GeV
$$^2$$
2
, would be made possible by the addition of a positron source at Jefferson Lab.
MIT Department
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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Creative Commons Attribution
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DOI of Published Version
https://doi.org/10.1140/epja/s10050-022-00682-1
