Measurements of the Neutron Magnetic Form Factor and the Two-Photon Exchange Contribution to the Electron-Neutron Elastic Scattering Cross Section

Author: ORCID icon
Boyd, John, Physics - Graduate School of Arts and Sciences, University of Virginia
Liyanage, Nilanga, AS-Physics (PHYS), University of Virginia

The Super BigBite Spectrometer (SBS) program in Experimental Hall A of Jefferson Lab is a series of high-precision, large Q-squared, electromagnetic form factor experiments. GMn and nTPE were the first two experiments of the SBS program and ran from October 2021 through February 2022. Both experiments detect neutron-tagged d(e,e'n) and proton-tagged d(e,e'p) quasi-elastic electrons scattering from a deuterium target. The GMn experiment is a measurement of the magnetic form factor of the neutron, GMn, via the ratio method over a Q-squared range of 3.5 to 13.5 (GeV/c)^(2). The nTPE experiment ran in-parallel with the GMn experiment and shared an overlapping kinematic point with GMn. nTPE extends the GMn experiment to assess the differences between Rosenbluth Slop and the single-photon exchange approximation. The nTPE experiment had two kinematic settings corresponding to different electron scatting angles at a fixed Q-squared values of 4.5 (GeV/c)^(2). Comparisons of nucleon form factor ratio measurements acquired through polarization transfer and LT separation reveal discrepancies as Q-squared increases. Two-photon exchange is strongly favored as the reason for this discrepancy. GMn has been extracted at two kinematic settings corresponding to Q-squared values of 3.0 and 4.5 (GeV/c)^(2). Additionally, I will present an assessment of the differences between Rosenbluth Separation and single-photon exchange measurements.

PHD (Doctor of Philosophy)
Electromagnetic form factors, Form Factors, EMFF, Super BigBite Spectrometer, SBS, Jefferson Lab, Thomas Jefferson National Accelerator Facility, JLab, Hall A, Experimental Hall A, GMn, gmn, nTPE, ntpe, form factors, magnetic form factor, neutron magnetic form factor, neutron electric form factor, GEn, magnetic form factor of the neutron, form factor ratio problem, form factor ratio puzzle, Rosenbluth Slope, Rosenbluth Separation, Rosenbluth Technique, LT Separation, Polarization transfer, Ratio Method, Durand Technique, Standard Model, physics, nucleon structure, nuclear physics, experimental nuclear physics, proton, neutron, electron, electron beam, electron scattering, electron-nucleon scattering, electron-proton scattering, electron-neutron scattering, single photon exchange, single-photon exchange, two photon exchange, two-photon exchange, the, TPE, GEM, GEM detector, GEM detectors, GEM R&D, GEMs, Gas Electron Multiplier, Gas electron multipliers, radiation, radiation detector, radiation detectors, quasi-elastic electron scattering, Electromagnetic Form Factor, form factor
Sponsoring Agency:
Thomas Jefferson National Accelerator FacilityDepartment of Energy
All rights reserved (no additional license for public reuse)
Issued Date: