Prospects for Charged Current Deep-Inelastic Scattering off Polarized Nucleons at a Future Electron-Ion Collider

TL;DR

This work evaluates charged-current deep-inelastic scattering off longitudinally polarized nucleons at a future Electron-Ion Collider. It introduces and utilizes a polarized version of the DJANGOH event generator to simulate CC DIS with radiative corrections, and it validates the Jacquet-Blondel method for kinematic reconstruction from the hadronic final state. The study shows that CC spin asymmetries are sizable and can significantly tighten global NLO determinations of helicity PDFs, especially when neutron-target data with spectator tagging are included. The results highlight CC DIS as a powerful, hadronization-independent probe of flavor-separated helicity parton distributions and outline avenues for further extensions.

Abstract

We present a detailed phenomenological study of charged-current-mediated deep-inelastic scattering off longitudinally polarized nucleons at a future Electron-Ion Collider. A new version of the event generator package DJANGOH, extended by capabilities to handle processes with polarized nucleons, is introduced and used to simulate charged current deep-inelastic scattering including QED, QCD, and electroweak radiative effects. We carefully explore the range of validity and the accuracy of the Jacquet-Blondel method to reconstruct the relevant kinematic variables from the measured hadronic final state in charged current events, assuming realistic detector performance parameters. Finally, we estimate the impact of the simulated charged current single-spin asymmetries on determinations of helicity parton distributions in the context of a global QCD analysis at next-to-leading order accuracy.

Figures (9)

• Figure 1: LO and NLO polarized CC DIS structure functions $g_i^{W^{-},N}$ for protons (top) and neutrons (bottom) as a function of $x$ at $Q^2=1000\,\mathrm{GeV}^2$ using the DSSV helicity PDFs deFlorian:2008mr.
• Figure 2: [color online] Radiative correction factor $r_\sigma$ as defined in (\ref{['eq:rsigma']}) for unpolarized CC electron scattering off protons for $x$-$Q^2$ bins accessible at an EIC with $\sqrt{S}\simeq141\,\mathrm{GeV}$.
• Figure 3: [color online] As in Fig. \ref{['fig:rc1']} but now for the single-spin asymmetry $A_L^{W^{-},p}$.
• Figure 4: [color online] Top left to bottom left panels: correlations between the reconstructed kinematic variables $y_{JB}$, $x_{JB}$, and $Q^2_{JB}$, including detector and radiative effects, and the true generated values. Lower right plot: purity in each $x,\,Q^2$ bin, measured as how many events that were generated in a bin remain in that bin after reconstruction (see text). All results are obtained for lepton and proton beam energies of $20\times250\,\mathrm{GeV}$, i.e. $\sqrt{S}\sim 141\,\mathrm{GeV}$.
• Figure 5: Integrated unpolarized CC electron-proton DIS cross section at NLO accuracy as a function of the c.m.s. energy $\sqrt{S}$ for $Q^2>Q^2_{\min}$ and $0.01\le y \le 0.95$. For comparison we also show the result for electron-neutron scattering (dashed line) for $Q^2_{\min}=100\,\mathrm{GeV}$.