Polarized Parton Distributions at an Electron-Ion Collider

Abstract

We study the potential impact of inclusive deep-inelastic scattering data from a future electron-ion collider (EIC) on longitudinally polarized parton distribution (PDFs). We perform a PDF determination using the NNPDF methodology, based on sets of deep-inelastic EIC pseudodata, for different realistic choices of the electron and proton beam energies. We compare the results to our current polarized PDF set, NNPDFpol1.0, based on a fit to fixed-target inclusive DIS data. We show that the uncertainties on the first moments of the polarized quark singlet and gluon distributions are substantially reduced in comparison to NNPDFpol1.0, but also that more measurements may be needed to ultimately pin down the size of the gluon contribution to the nucleon spin.

Figures (7)

• Figure 1: Kinematic coverage in the $(x,Q^2)$ plane for the fixed-target experimental data included in the NNPDFpol1.0 polarized parton fit Ball:2013lla and the EIC pseudodata from Aschenauer:2012ve. The shaded bands show the expected kinematic reach of each of the two EIC scenarios discussed in the text.
• Figure 2: Value of the $\chi^2$ per data point for the datasets included in the NNPDFpolEIC-A (left) and in the NNPDFpolEIC-B (right) fits, compared to NNPDFpol1.0Ball:2013lla. The horizontal lines correspond to the unweighted average of the $\chi^2$ values shown, and the one-sigma interval about it. The dashed lines refer to NNPDFpolEIC-A (left plot) or NNPDFpolEIC-B (right plot) fits, while the dot-dashed lines refer to NNPDFpol1.0Ball:2013lla.
• Figure 3: The NNPDFpolEIC-A parton distributions at $Q_0^2=1$ GeV$^2$ plotted as a function of $x$ on a logarithmic scale, compared to NNPDFpol1.0Ball:2013lla.
• Figure 4: Same as Fig. \ref{['fig:PDFsEIC1']}, but for NNPDFpolEIC-B, compared to NNPDFpol1.0Ball:2013lla.
• Figure 5: The polarized gluon PDF $\Delta g(x,Q_0^2)$, at $Q_0^2=1$ GeV$^2$ (upper panels) and at $Q^2=10$ GeV$^2$ (lower panels), in the NNPDFpolEIC PDF sets, compared to DSSV deFlorian:2009vb and to NNPDFpol1.0Ball:2013lla.