Muon capture

Muon capture is the capture of a negative muon by a proton, usually resulting in production of a neutron and a neutrino, and sometimes a gamma photon.

Feynman diagram of the muon capture. A negatively charged muon is captured by a proton. The proton is transformed into a neutron and a muon-neutrino is emitted. The interaction is mediated by a W-boson.

Muon capture by heavy nuclei often leads to emission of particles; most often neutrons, but charged particles can be emitted as well.

Ordinary muon capture (OMC) involves capture of a negative muon from the atomic orbital without emission of a gamma photon:

μ⁻
 + 
p⁺
 → 
ν
_μ + 
n⁰

Radiative muon capture (RMC) is a radiative version of OMC, where a gamma photon is emitted:

μ⁻
 + 
p⁺
 → 
ν
_μ + 
n⁰
 + 
γ

One motivation for the study of muon capture on the proton is its connection to the proton's induced pseudoscalar form factor g_p.