The Michel electron is what we call the electron produced from muon decay, and it's named after Louis Michel. I mention this in a paper I'm writing, and I was told that I need to cite it. I can't find anything that explains the origin of the name, much less a paper that's citeable. Does anyone have any insights into this, or even more appreciated, knowledge of a paper that I could cite for this?

In 1935 Yukawa proposed that nucleon interaction is mediated by a new particle, which he termed "meson" because its mass was predicted to be intermediate between electron and nucleon. In 1937 Neddermeyer and Anderson discovered a candidate for such a particle in cosmic rays, which was called "$\mu$ meson". However, after the war new experiments showed in 1947 that "$\mu$ meson" neither interacted strongly with matter, nor decayed as predicted. So it couldn't have been Yukawa's particle. Rabi even quipped "who ordered that?" about it, and the name "$\mu$ meson" was shortened to the modern "muon".

Experiments soon revealed the manner of muon's decay, into an electron and a pair of neutrinos, and the shape of the electron spectrum was first calculated by Louis Michel in 1950. This is where "Michel electron" comes from. Michel introduced a single parameter $\rho$ to describe the shape. However, after the non-conservation of parity in weak interactions proposal of Lee and Yang three more parameters ($\eta$, $\xi$ and $\delta$) had to be added, and now all four are referred to collectively as "Michel parameters".

Depommier's paper gives more historical details, and a reference to the Michel's 1950 paper Interaction between Four Half-Spin Particles and the Decay of the $\mu$-Meson.

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.