Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider

Abstract

We present a first determination of the nuclear parton distribution functions (nPDF) based on the NNPDF methodology: nNNPDF1.0. This analysis is based on neutral-current deep-inelastic structure function data and is performed up to NNLO in QCD calculations with heavy quark mass effects. For the first time in the NNPDF fits, the ${\chi }^2$ minimization is achieved using stochastic gradient descent with reverse-mode automatic differentiation (backpropagation). We validate the robustness of the fitting methodology through closure tests, assess the perturbative stability of the resulting nPDFs, and compare them with other recent analyses. The nNNPDF1.0 distributions satisfy the boundary condition whereby the NNPDF3.1 proton PDF central values and uncertainties are reproduced at $A=1$, which introduces important constraints particularly for low-$A$ nuclei. We also investigate the information that would be provided by an Electron-Ion Collider (EIC), finding that EIC measurements would significantly constrain the nPDFs down to $x\simeq 5\times 10^{-4}$. Our results represent the first-ever nPDF determination obtained using a Monte Carlo methodology consistent with that of state-of-the-art proton PDF fits, and provide the foundation for a subsequent global nPDF analyses including also proton-nucleus data.

50 pages, 24 figures

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• LHAPDF6: parton density access in the LHC precision era
• Parton distributions in the LHC era: MMHT 2014 PDFs
• Determination of nuclear parton distribution functions and their uncertainties at next-to-leading order
• Thermal Dileptons at LHC
• Heavy-Quark Kinetics in the QGP at LHC
• aMCfast: automation of fast NLO computations for PDF fits
• Nuclear Structure Functions at a Future Electron-Ion Collider
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• Neutrino Structure Functions from GeV to EeV Energies
• Phenomenology of NNLO jet production at the LHC and its impact on parton distributions
• Charting the low-loss region in Electron Energy Loss Spectroscopy with machine learning
• Role of nuclear gluon distribution on particle production in heavy ion collisions
• Proton-PDF uncertainties in extracting nuclear PDFs from $W^{\pm }$ production in p+Pb collisions
• Impact of scale, nuclear PDF and temperature variations on the interpretation of medium-modified jet production data from the LHC
• Constraints of the Low-x Structure of Protons and Nuclei