Target-normal single spin asymmetries measured with positrons
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10050_2021_531_ReferencePDF.pdf
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Author(s)
Grauvogel, G. N.
Kutz, T.
Schmidt, A.
Date Issued
June 29, 2021
Publisher
Springer Berlin Heidelberg
Citation
The European Physical Journal A. 2021 Jun 29;57(6):213
Version
Author's final manuscript
Abstract
Abstract
Two-photon exchange and the larger class of hadronic box diagrams are difficult to calculate without a large degree of model-dependence. At the same time, these processes are significant radiative corrections in parity-violating electron scattering, in neutron decay, and may even be responsible for the proton’s form factor ratio discrepancy. New kinds of experimental data are needed to help constrain models and guide future box-diagram calculations. The target-normal single spin asymmetry,
$$A_n$$
A
n
, formed with an unpolarized beam scattering from a target that is polarized normal to the scattering plane, is sensitive to the imaginary part of the two-photon exchange amplitude, and can provide a valuable constraint. A measurement with both electrons and positrons can reduce sources of experimental error, and distinguish between the effects of two-photon exchange and those of time-reversal symmetry violation. This article describes a proposed experiment in Hall A, using the new Super Big-Bite Spectrometer that can cover a momentum transfer range in the critical zone of uncertainty between where hadronic calculations and those based on partonic degrees of freedom are expected to be accurate.
MIT Department
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1140/epja/s10050-021-00531-7
