Nuclear Structure Functions at a Future Electron-Ion Collider

TL;DR

This paper investigates how a future Electron-Ion Collider can significantly improve our understanding of the low-$x$ nuclear structure functions, especially the gluon distribution, through simulated measurements and global fits.

Contribution

It demonstrates the potential of an EIC to constrain nuclear parton distribution functions, particularly the gluon PDF, at low $x$ with reduced uncertainties.

Findings

EIC measurements can substantially improve constraints on nuclear gluon PDFs.

Simulated data analysis shows reduced uncertainties in nuclear structure functions.

The study emphasizes the importance of EIC for exploring non-linear QCD effects at low $Q^2.

Abstract

The quantitative knowledge of heavy nuclei's partonic structure is currently limited to rather large values of momentum fraction $x$ -- robust experimental constraints below $x \sim 10^{-2}$ at low resolution scale $Q^2$ are particularly scarce. This is in sharp contrast to the free proton's structure which has been probed in deep inelastic scattering (DIS) measurements down to $x \sim 10^{-5}$ at perturbative resolution scales. The construction of an Electron-Ion Collider (EIC) with a possibility to operate with a wide variety of nuclei, will allow one to explore the low-$x$ region in much greater detail. In the present paper we simulate the extraction of the nuclear structure functions from measurements of inclusive and charm reduced cross sections at an EIC. The potential constraints are studied by analyzing simulated data directly in a next-to-leading order global fit of nuclear parton distribution functions based on the recent EPPS16 analysis. A special emphasis is placed on studying the impact an EIC would have on extracting the nuclear gluon PDF, the partonic component most prone to non-linear effects at low $Q^2$. In comparison to the current knowledge, we find that the gluon PDF can be measured at an EIC with significantly reduced uncertainties.