PDFs from nucleons to nuclei
Alberto Accardi
TL;DR
The paper discusses unpolarized parton distribution functions (PDFs) in protons and nuclei from a unified perspective, emphasizing the universality of PDFs and their use in global fits that combine high-energy collider data with lower-energy nuclear data. It highlights advances in proton PDF determinations, including target mass corrections, higher-twist effects, and deuteron corrections, and discusses the large-$x$ frontier and the $d/u$ ratio as $x\to 1$, alongside the role of forward-rapidity measurements and threshold resummation. The text then examines the interplay between proton and nuclear data through deuteron targets, showing how global fits can constrain nuclear corrections and improve flavor separation, particularly for $d$ and $u$ at large $x$. It also surveys neutrino-nucleus dimuon production as a probe of strange PDFs, the challenges of initial- and final-state nuclear effects, and how LHC data on $W+c$ can help disentangle these effects. Finally, it reviews nuclear PDFs (nPDFs), competing parametrizations, data tensions between neutrino and charged-lepton scattering, and future directions to extend kinematic reach and integrate nuclear and proton fits into a coherent description of parton dynamics in nuclei and nucleons.
Abstract
I review recent progress in the extraction of unpolarized parton distributions in the proton and in nuclei from a unified point of view that highlights how the interplay between high energy particle physics and lower energy nuclear physics can be of mutual benefit to either field. Areas of overlap range from the search for physics beyond the standard model at the LHC, to the study of the non perturbative structure of nucleons and the emergence of nuclei from quark and gluon degrees of freedom, to the interaction of colored probes in a cold nuclear medium.