Solving the Muon Puzzle in air showers initiated by high-energy cosmic rays with LHCb

• Applicant: Dr. Hans Dembinski
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields ; Astrophysics and Astronomy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449728698

High-energy cosmic rays are messengers of the extreme non-thermal universe. These rays can only be studied through the observation of air showers, extensive particle cascades produced by interactions with Earth's atmosphere. The sources of high-energy cosmic rays are unclear. The key to narrow down potential sources is to measure the elemental composition of the rays. The composition can be inferred from observable air shower features, but this requires accurate air shower simulations. Studies have shown that one of the two main air shower features, the total number of muons produced in the shower, is not correctly predicted by current air shower simulations. Resolving this so called Muon Puzzle requires precision measurements of the inclusive forward production to a few percent of prompt pions, kaons, protons, and the ratio of prompt electromagnetic and hadronic energy flows in proton-proton collisions at 13 TeV and proton-Blei collisions at 8.16 TeV with the LHCb experiment. Measurements to 5 % can be realistically achieved and would reduce the current model spread fivefold. We propose to carry out these measurements and to calculate their effect on air shower simulations. Projections have shown that these improvements can resolve the Muon Puzzle and the ambiguity in the inferred elemental composition of high-energy cosmic rays, which would solve a core problem of the cosmic ray community with enormous impact on current and future astroparticle experiments.

• DFG Programme: Research Grants