Measurement of the neutron F2 structure function via spectator tagging with CLAS

TL;DR

This paper presents the first precise measurement of the neutron F2 structure function using spectator tagging in electron-deuterium scattering, covering a wide kinematic range with minimal nuclear correction uncertainties.

Contribution

It introduces a novel spectator tagging technique to accurately extract the neutron F2 structure function from semi-inclusive scattering data.

Findings

First measurement of F2n over a broad x range with low nuclear correction uncertainty.

Determination of the neutron to proton structure function ratio F2n/F2p at 0.2 < x < 0.8.

Data covers both resonance and deep-inelastic regions.

Abstract

We report on the first measurement of the F2 structure function of the neutron from semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to < 100 MeV and their angles to < 100 degrees relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F2n data collected cover the nucleon resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65 < Q2 < 4.52 GeV2, with uncertainties from nuclear corrections estimated to be less than a few percent. These measurements provide the first determination of the neutron to proton structure function ratio F2n/F2p at 0.2 < x < 0.8 with little uncertainty due to nuclear effects.