Measurement of the neutron electric to magnetic form factor ratio at Q2 = 1.58 GeV2 using the reaction 3He(e,e'n)pp

TL;DR

This paper reports a precise measurement of the neutron's electric to magnetic form factor ratio at a specific momentum transfer using polarized electron scattering off polarized helium-3, providing insights into neutron structure.

Contribution

It presents a novel experimental determination of GEn/GMn at Q2 = 1.58 GeV2 using a double ratio method with polarized targets and electrons, reducing systematic uncertainties.

Findings

Measured GEn/GMn ratio at Q2 = 1.58 GeV2

Achieved reduced systematic errors through target polarization orientations

Provided data consistent with theoretical models of neutron structure

Abstract

A measurement of beam helicity asymmetries in the reaction 3He(e,e'n)pp has been performed at the Mainz Microtron in quasielastic kinematics in order to determine the electric to magnetic form factor ratio of the neutron, GEn/GMn, at a four momentum transfer Q2 = 1.58 GeV2. Longitudinally polarized electrons were scattered on a highly polarized 3He gas target. The scattered electrons were detected with a high-resolution magnetic spectrometer, and the ejected neutrons with a dedicated neutron detector composed of scintillator bars. To reduce systematic errors data were taken for four different target polarization orientations allowing the determination of GEn/GMn from a double ratio. We find mu_n GEn/GMn = 0.250 +/- 0.058(stat.) +/- 0.017 (sys.).