Muons are generated in the Earth's upper atmosphere by cosmic rays (high energy protons) colliding with atomic nuclei

of molecules in the air. ... We can form surface muon beams from pions decaying at the surface of the target. That beam is made of positive muons only, as the negative muons are captured.

Where are muons made?

Muons are produced in interactions that occur in the high atmosphere between nuclei of gaseous molecules and primary cosmic rays, which are mostly high-energy protons.

How are muons produced in a lab?

Muons are produced at PSI in very violent collisions, involving fast protons extracted from the main particle accelerator which then collide with a rotating carbon ring target; amongst the new particles created from these collisions are muons, which can then be used for experiments.