Tagged spectator deep-inelastic scattering off the deuteron as a tool to study neutron structure

TL;DR

This paper presents a model for deep-inelastic scattering off deuterons with spectator protons, enabling extraction of neutron structure functions and revealing unexpected behavior at high Bjorken x.

Contribution

It introduces a virtual nucleon approximation model that accounts for final-state interactions and uses pole extrapolation to determine neutron structure functions from experimental data.

Findings

Neutron to proton structure function ratio may rise at high x

Model fits to high-momentum spectator data

Application of pole extrapolation to BONuS data

Abstract

We give an overview of a model to describe deep-inelastic scattering (DIS) off the deuteron with a spectator proton, based on the virtual nucleon approximation (VNA). The model accounts for the final-state interactions (FSI) of the DIS debris with the spectator proton. Values of the rescattering cross section are obtained by fits to high-momentum spectator data. By using the so-called "pole extrapolation method", free neutron structure functions can be obtained by extrapolating low-momentum spectator proton data to the on-shell neutron pole. We apply this method to the BONuS data set and find a surprising Bjorken $x$ dependence, indicating a possible rise of the neutron to proton structure function ratio at high $x$.