# Can muonic atoms exist?

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.

• The extremely low half-life of muons is a large contributing factor to why we don't see more of them. – John Dvorak May 15 at 11:25

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.

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

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

• 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 – anna v May 15 at 18:10
• @annav That is because of their speed. They travel so fast that due to time dilation their lifetime is years. – Manvendra Somvanshi May 16 at 4:25

No muons and tauons are very heavy and decay almost instantly to electrons.

• Muons live for a long time by particle physics standards. Certainly long enough to form muonic atoms. – Chris May 15 at 15:02
• You cant know how muons can live Chris even the half life time is an approximation for most muons. – Flawless May 15 at 15:22
• That's irrelevant. Some muons might not live long enough to form muonic atoms, but most of them do. – Chris May 15 at 15:26
• Considering that's millions of times longer than the tau lifetime, yes, that is a long time. For a lifetime to be too short to form an atom, it needs to be on the order of $r_{\rm atom}\over\rm c$, many orders of magnitude less than that of the muon. – Chris May 15 at 15:37
• Muonic atoms, and particularly muonic hydrogen, are very much possible, and an ongoing platform of experimental research. (See e.g. their role in the research on the so-called 'proton radius puzzle'.) The $\mu^-\to e^-$ decay lifetime is short by human standards, but it is perfectly long enough for the muons to be captured into atoms and to perform spectroscopy on those atoms. – Emilio Pisanty May 15 at 17:08