The Muon Puzzle in Ultra-High-Energy Air Showers, Priced: The Per-Generation Neutral-Pion Shift the Auger Deficit Requires, and What Accelerators Allow
Year: 2026
Type: article
Abstract: Air showers above about 10 EeV contain more muons than any current hadronic interaction model predicts for the composition inferred from the depth of shower maximum. Adopting a muon enhancement factor R_mu = 1.45 at 10 EeV (published range 1.30-1.60) and R_mu = 1.62 at 100 EeV, a calibrated Heitler-Matthews cascade (4.94 generations at 10 EeV, effective multiplicity 57.7, baseline beta = 0.90) is used to compute the per-generation change in the neutral-pion energy fraction f0 that would accumulate to the observed enhancement. Uniform placement: f0 must fall from 0.333 to 0.281 at 10 EeV (-15.6%) and to 0.272 at 100 EeV (-18.4%) -- inside an adopted +/-20% accelerator band in size, but forbidden in placement, since most generations occur at energies already measured. Restricted to the 1.14 generations above LHC proton-proton energy: f0 must fall to 0.076 at 10 EeV (-77.1%) and 0.115 at 100 EeV (-65.6%), roughly four times outside the band set by LHCf forward neutral-pion spectra, FASER forward neutrino fluxes, and the July 2025 LHC proton-oxygen run. Verdict: no placement of the required change is simultaneously sufficient and accelerator-allowed.
Author: Aldred, William Alexander
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7225729304
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