Constraining the strangeness enhancement scenario of the UHECR muon puzzle with LHC experiments

Abstract: The excess of muons observed in ultra-high-energy cosmic-ray air showers relative to simulation predictions, known as the muon puzzle, provides indirect evidence of our incomplete understanding of high-energy hadronic interactions. An unambiguous resolution requires that each proposed solution be directly tested through collider experiments probing hadronic interactions. In this work, we develop a framework to assess the strangeness enhancement scenario, wherein an increased yield of kaons relative to pions boosts muon production. Using the MCEQ air-shower simulation package, we first identify the key phase-space regions of hadronic interactions that drive muon yields in this scenario. We then demonstrate that combining Pierre Auger Observatory muon measurements with forthcoming kaon-to-pion ratio data from LHC Run~3 can robustly constrain the scenario's parameters. In particular, we find that achieving 10.8% precision on the kaon-to-pion ratio at LHCb and 8.4% at FASER is sufficient to test the strangeness enhancement hypothesis over its viable parameter space. These upcoming experimental results will provide the first direct constraints on strangeness enhancement as a potential resolution of the muon puzzle.