The Muon Puzzle in High-Energy Air Showers

Аннотация

The Muon Puzzle is a long-standing issue in the observation of high-energy cosmic rays. In 2018, eight leading air shower experiments combined their data on muons in high-energy air showers and established the existence of an energy-dependent offset with a significance of 8σ. The muon abundance is an important indicator for the cosmic ray mass. The Muon Puzzle needs to be solved to infer the cosmic-ray mass composition unambiguously. It also presents a unique opportunity to learn more about nonperturbative QCD in hadron—nucleus collisions. We will review the status of the Muon Puzzle and discuss an outlook for the future.