Why is a semileptonic decay mode called so?

I mean, if there is one lepton amongst the decay products, it should be leptonic, right?

If there are two, that should be called bi-leptonic or something like that?

Why is the former called a semileptonic mode, and the latter called leptonic?

What is this "semi" in semileptonic?


1 Answer 1


Strictly speaking the prefix semi means half, but it's often used in the sense of partial. A good example of this would be semiconductor.

So semileptonic just means partially leptonic.

  • $\begingroup$ Thanks. So, if I get this correctly, you mean semileptonic decay is that decay where you have a non-lepton + a lepton as products, and leptonic decay is that one where the products are exclusively lepton(s), i.e. no non-leptons? $\endgroup$ Oct 5, 2014 at 15:40
  • $\begingroup$ @UserAnonymous: yes, that's my interpretation. $\endgroup$ Oct 5, 2014 at 15:55
  • $\begingroup$ yes that seems to make a lot of sense. Thanks again. $\endgroup$ Oct 5, 2014 at 15:56

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