https://doi.org/10.1140/epjc/s10052-024-12665-1
Regular Article - Theoretical Physics
The LHC as a Neutrino-Ion Collider
1
CERN, Theoretical Physics Department, 1211, Geneva 23, Switzerland
2
Department of Physics and Astronomy, University of California, 92697, Irvine, CA, USA
3
Department of Physics and Astronomy, Vrije Universiteit, 1081 HV, Amsterdam, The Netherlands
4
Nikhef Theory Group, Science Park 105, 1098 XG, Amsterdam, The Netherlands
5
National Centre for Nuclear Research, Pasteura 7, 02-093, Warsaw, Poland
Received:
28
September
2023
Accepted:
10
March
2024
Published online:
8
April
2024
Proton-proton collisions at the LHC generate a high-intensity collimated beam of neutrinos in the forward (beam) direction, characterised by energies of up to several TeV. The recent observation of LHC neutrinos by FASER
and SND@LHC signifies that this previously overlooked particle beam is now available for scientific investigation. Here we quantify the impact that neutrino deep-inelastic scattering (DIS) measurements at the LHC would have on the parton distributions (PDFs) of protons and heavy nuclei. We generate projections for DIS structure functions for FASER and SND@LHC at Run III, as well as for the FASER2, AdvSND, and FLArE experiments to be hosted at the proposed Forward Physics Facility (FPF) operating concurrently with the High-Luminosity LHC (HL-LHC). We determine that up to one million electron-neutrino and muon-neutrino DIS interactions within detector acceptance can be expected by the end of the HL-LHC, covering a kinematic region in x and 
overlapping with that of the Electron-Ion Collider. Including these DIS projections in global (n)PDF analyses, specifically PDF4LHC21, NNPDF4.0, and EPPS21, reveals a significant reduction in PDF uncertainties, in particular for strangeness and the up and down valence PDFs. We show that LHC neutrino data enable improved theoretical predictions for core processes at the HL-LHC, such as Higgs and weak gauge boson production. Our analysis demonstrates that exploiting the LHC neutrino beam effectively provides CERN with a “Neutrino-Ion Collider” without requiring modifications in its accelerator infrastructure.
© The Author(s) 2024
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Funded by SCOAP3.
