# Muon capture

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**Muon capture** is the capture of a negative [muon](/source/Muon) by a [proton](/source/Proton), usually resulting in production of a [neutron](/source/Neutron) and a [neutrino](/source/Neutrino), and sometimes a [gamma](/source/Gamma_ray) [photon](/source/Photon).

Except for the flavor of neutrino, it has exactly the same result as [electron capture](/source/Electron_capture), except that the great mass-energy of the muon makes it allowed for all nuclei and there is so much excess energy that a nucleus can disintegrate; for heavy nuclei this leads to emission of nuclear particles; most often [neutrons](/source/Neutron), 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 +

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

- + → μ + +

Theoretical motivation for the study of muon capture on the proton is its connection to the proton's induced pseudoscalar [form factor](/source/Form_factor_(quantum_field_theory)) gp [1]'

The most precise measurement of the muon capture rate on the proton 𝛬𝑆 =(714.9 ±5.4stat ±5.1syst)��� s−1 and the induced pseudoscalar coupling constant gp⁡=8.06 ±0.55 was done by the MUCAP experiment [2,3] with a measurement performed at the [Paul Scherrer Institut](/source/Paul_Scherrer_Institute), Switzerland. The result is in excellent agreement with theoretical precidtions [1].

## Nuclear waste disposal

Muon capture is being investigated for practical application in radioactive waste disposal, for example in the [artificial transmutation](/source/Nuclear_transmutation) of large quantities of long-lived [radioactive waste](/source/Radioactive_waste) that have been produced globally by [fission reactors](/source/Nuclear_reactor). Radioactive waste can be transmuted to stable isotopes following irradiation by an incident muon () beam from a compact [proton accelerator](/source/Particle_accelerator) source.

## References

[1] T. Gorringe and H.W. Fearing (2004). "Induced pseudoscalar coupling of the proton weak interaction". *Rev. Mod. Phys.*. **76** (1): 31–91. [arXiv:nucl-th/0206039](https://arxiv.org/abs/nucl-th/0206039). [Bibcode:2003RvMP...76...31G](https://ui.adsabs.harvard.edu/abs/2003RvMP...76...31G). [doi:10.1103/RevModPhys.76.31](https://doi.org/10.1103/RevModPhys.76.31)

[2] V.A. Andreev et al. (2007). "Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's Pseudoscalar Coupling gP". *Physical Review Letters*. **99** (3). [arXiv:0704.2072](https://arxiv.org/abs/0704.2072). [Bibcode:2007PhRvL..99c2002A](https://ui.adsabs.harvard.edu/abs/2007PhRvL..99c2002A). [doi:10.1103/PhysRevLett.99.032002](https://doi.org/10.1103/PhysRevLett.99.032002). [PMID 17678281](https://pubmed.ncbi.nlm.nih.gov/17678281)

[3] V.A.Andreev et al, (2013) ["Measurement of Muon Capture on the Proton to 1% Precision and Determination of the Pseudoscalar Coupling 𝑔𝑃" Physical Review Letters 110 (3) 012504](https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.012504) DOI: [https://doi.org/10.1103/PhysRevLett.110.012504](https://doi.org/10.1103/PhysRevLett.110.012504)

[4] [Nagamine, Kanetada (2016) "Nuclear Waste Disposal Method and its apparatus using muon-nuclear-absorption". (WO2016143144A1)](https://worldwide.espacenet.com/patent/search/family/056878645/publication/WO2016143144A1?q=pn%3DWO2016143144A1) [Espacenet](/source/Espacenet) (Patent database).

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