Astroparticle Physics at the Forward Physics Facility

Abstract: High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC) will generate a substantial flux of particles along the beam collision axis that current LHC experiments cannot access. Multi-particle production in the far-forward region is particularly relevant to astroparticle physics. High-energy cosmic rays initiate extensive air showers (EASs) in the atmosphere, driven by hadron-ion collisions at low momentum transfer in the non-perturbative regime of QCD. Therefore, understanding high-energy hadronic interactions in the forward region is essential for interpreting EAS data and estimating backgrounds for astrophysical neutrino searches, among other applications. The Forward Physics Facility (FPF) is a proposal to construct a new underground cavern at the HL-LHC dedicated to hosting a range of experiments aimed at detecting particles beyond the current capabilities of LHC experiments. This article will provide an update on the current planning status of the FPF and emphasize its synergies with astroparticle physics.