Would it be possible in the standard model to have atom like systems in which muons (or tauons) take the place of electrons? Why don't we see more of them? For instance it could be related to some mechanism leptogenesys, but I don't know much about this subject..

How the difference between muonic and electronic atoms could affect astronomical data?

Correct me if I am wrong, but I guess there is no analogue for protons and neutrons, especially since protons have very long life.

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    $\begingroup$ The extremely low half-life of muons is a large contributing factor to why we don't see more of them. $\endgroup$ May 15, 2019 at 11:25

3 Answers 3


Absolutely they can exist. In fact, physicists often creat muonic hydrogen to study things like the structure/size of the proton with more accuracy.

The reason we don't see muonic/tauonic atoms in nature is that these particles decay very quickly, whereas the electron, being the lightest of the three generations of leptons, has an essentially infinite lifetime.

  • $\begingroup$ Thanks I understand. But if the decay was QED you should always get another muon.. is it an electroweak decay? $\endgroup$
    – AoZora
    May 15, 2019 at 12:17
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    $\begingroup$ @france95 it decays via the weak force. $\endgroup$ May 15, 2019 at 12:24
  • $\begingroup$ This may also be interesting: en.wikipedia.org/wiki/Exotic_atom $\endgroup$
    – GRB
    Jun 4, 2019 at 14:18

Muonic atoms can be made from one antimuon and one electron. The antimatter version of this antimuonium is where one muon is orbited by a positron. The decay product goes like this:

Now the electron orbits the W+ boson and normally the W+ would decay into a positron and neutrino. However electron and W+ react way before that. This results in electron neutrino. Th end products are anti-muon neutrino and electron neutrino


$\mathrm W^++e^-={v_e}$

Muonium decays to muon neutrino and electron antineutrino in little over 2.2 microseconds(the life time of muons).

For antimuonium decay here is the equation:


$\mathrm W^-+e^+=\bar{v_e}$

Here there is a muon neutrino and an antielectron neutrino.


Muons and tauons are very heavy and unstable particles. They generally decay into electron that is why they are rarely found in nature.

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    $\begingroup$ Not so rarey because muons are the main component of cosmic rays, about one muon per second per meter centimeter cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm $\endgroup$
    – anna v
    May 15, 2019 at 18:10
  • $\begingroup$ @annav That is because of their speed. They travel so fast that due to time dilation their lifetime is years. $\endgroup$ May 16, 2019 at 4:25

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