Speaker
Description
High-energy cosmic rays interacting in the Earth’s atmosphere produce extensive air showers that are observed by large ground-based detector arrays. The properties of the primary cosmic ray must be inferred indirectly from the secondary particles measured at the surface, a process that relies strongly on theoretical models of hadronic interactions during shower development. Over the past two decades, various experiments have measured the muon content of extensive air showers across several orders of magnitude in cosmic-ray energy. These measurements reveal significant discrepancies between observed muon densities and predictions from simulations based on QCD-inspired phenomenological models. Despite substantial efforts to improve the modeling of muon production - incorporating constraints from both cosmic-ray and accelerator data - these differences persist and are commonly known as the muon puzzle.
In this contribution, I will present a comprehensive review of muon measurements in extensive air showers from multiple cosmic-ray experiments and discuss their consistency with predictions from a range of phenomenological models. I will summarize key insights gained over the past decade and highlight recent advances in both the measurement and modeling of muon production in air showers, with particular emphasis on their implications for cosmic-ray composition studies and multi-messenger astrophysics.