Neutron spin structure from polarized deuteron DIS with proton tagging

Abstract

Polarized electron-deuteron deep-inelastic scattering (DIS) with detection of the spectator proton ("tagged DIS") enables measurements of neutron spin structure with maximal control of nuclear effects. We calculate the longitudinal spin asymmetries in polarized tagged DIS using methods of light-front nuclear structure and study their dependence on the measured proton momentum. Asymmetries can be formed with all three deuteron spin states (±1, 0) or the two maximum-spin states only (±1, involving tensor polarization). The proton momentum dependence can be used to select pure S-wave configurations in the deuteron and eliminate D-wave depolarization (transverse momenta p pT 100 MeV). Free neutron spin structure can be extracted model-independently through pole extrapolation of the tagged asymmetries. Such measurements could be performed at a future electron-ion collider (EIC) with polarized deuteron beams and forward proton detectors.

Deep-inelastic electron-deuteron scattering with spectator nucleon tagging at the electron-ion collider. Extracting free nucleon structure

“…The measured spectator momentum controls the D/S wave ratio in the deuteron and thus fixes the spin structure of the pn configuration during the high-energy process. This feature can be used to eliminate D-wave depolarization in the extraction of neutron spin structure, or to maximize the D-wave in the exploration of vector-or tensor-polarized spin asymmetries [24][25][26]. The luminosity and polarization requirements of such measurements are under investigation [19,59].…”

“…In addition, deuteron DIS with proton or neutron tagging at higher momenta p p,n ∼ few 100 MeV/c selects small-size pn configurations with significant interactions and allows one to study the EMC effect as a function of the configuration size. Other applications include tagged DIS on the polarized deuteron (vector and tensor polarization) [24][25][26] and tagged diffractive scattering at small x [27,28].…”