Muoninduced

Muon-induced refers to processes in which muons—charged leptons with a mass about 207 times that of the electron and a mean lifetime of 2.2 microseconds in vacuum—initiate interactions as they traverse matter. Muons are produced in cosmic-ray air showers and in accelerator facilities, and their high penetrating power allows them to reach deep underground.

In matter, muons lose energy mainly through ionization, with additional stochastic energy loss via bremsstrahlung, electron-positron pair production, and occasionally photonuclear interactions at high energies. Negative muons can be captured by nuclei, a weak-interaction process that leads to nuclear transmutation and emission of neutrons, gamma rays, and other nuclear products. Muons can also initiate hadronic cascades (muon-induced spallation) when they interact with nuclei, producing neutrons and other secondaries.

Muons and their secondaries form backgrounds in underground experiments: direct muon tracks, muon-induced neutrons produced in surrounding rock or shielding, and delayed radioactive decays of spallation products. Accurate modeling of muon-induced backgrounds is important for rare-event searches in dark matter and neutrino experiments; experiments employ veto detectors, shielding, and simulation tools to mitigate these effects.

Muon-induced processes are also studied for cosmogenic nuclide production in Earth materials and for muon-induced neutron yields in materials science. The term muon-induced thus intersects several subfields, including muon spectroscopy, muon tomography, and underground physics.