Neutron spin structure with polarized deuterons and spectator proton tagging at EIC

TL;DR

This paper discusses how the Electron-Ion Collider can enable precise neutron structure measurements using polarized deuterons and spectator proton tagging, overcoming limitations of traditional nuclear target experiments.

Contribution

It introduces a novel spectator tagging method at EIC for accurate neutron structure determination, reducing nuclear effects and applicable to polarized and semi-inclusive scattering.

Findings

Spectator tagging allows neutron structure extraction with minimal nuclear corrections.

The method can be applied to polarized and semi-inclusive measurements.

EIC detector and accelerator requirements are outlined for successful implementation.

Abstract

The neutron's deep-inelastic structure functions provide essential information for the flavor separation of the nucleon parton densities, the nucleon spin decomposition, and precision studies of QCD phenomena in the flavor-singlet and nonsinglet sectors. Traditional inclusive measurements on nuclear targets are limited by dilution from scattering on protons, Fermi motion and binding effects, final-state interactions, and nuclear shadowing at x << 0.1. An Electron-Ion Collider (EIC) would enable next-generation measurements of neutron structure with polarized deuteron beams and detection of forward-moving spectator protons over a wide range of recoil momenta (0 < p_R < several 100 MeV in the nucleus rest frame). The free neutron structure functions could be obtained by extrapolating the measured recoil momentum distributions to the on-shell point. The method eliminates nuclear modifications and can be applied to polarized scattering, as well as to semi-inclusive and exclusive final states. We review the prospects for neutron structure measurements with spectator tagging at EIC, the status of R&D efforts, and the accelerator and detector requirements.