The muon is a subatomic particle that resembles an electron but is 200 times heavier. It interacts with nuclei through the weak force, one of the four fundamental forces in the universe. When a muon binds with a deuteron (composed of one proton and one neutron), it forms a system with two neutrons. This process is analogous to proton-proton fusion, where two protons combine to form a deuteron.
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Source: Phys.org