Regular Article - Experimental Physics
A measurement of two-photon exchange in Super-Rosenbluth separations with positron beams
Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA
2 Los Alamos National Laboratory, 87545, Los Alamos, NM, USA
Accepted: 14 November 2021
Published online: 29 November 2021
The proton electric and magnetic form factors, and , are intrinsically connected to the spatial distribution of charge and magnetization in the proton. For decades, Rosenbluth separation measurements of the angular dependence of elastic e-p scattering were used to extract and . More recently, polarized electron scattering measurements, aiming to improve the precision of extractions, showed significant disagreement with Rosenbluth measurements at large momentum transfers (). This discrepancy is generally attributed to neglected two-photon exchange (TPE) corrections. At larger values, a new ‘Super-Rosenbluth’ technique was used to improve the precision of the Rosenbluth extraction, allowing for a better quantification of the discrepancy, while comparisons of e-p and e-p scattering indicated the presence of TPE corrections, but at values below where a clear discrepancy is observed. In this work, we demonstrate the significant benefits to combining the Super-Rosenbluth technique with positron beam measurements. This approach provides a greater kinematic reach and is insensitive to some of the key systematic uncertainties in previous positron measurements.
© The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2021