Which of the following particles
have a lepton number of one? Muon, antitauon, tau neutrino,
electron antineutrino, tauon, tau antineutrino.
Alright, the first thing we can
realize is that any particle that has a lepton number of one is itself a lepton. A lepton is a subatomic elementary
particle that does not participate in the strong nuclear force. There are six kinds of leptons, the
electron, the muon, the tauon, and three types of neutrinos. And as we said, all six of these
particles have a lepton number of one. Looking at our answer options then,
we see that the muon, the tau neutrino, and the tauon are all leptons and therefore
have a lepton number of one, while the rest of the answer options all have a word
with this prefix anti- somewhere in it.
That tells us that these are
antiparticles. In particular, they’re
antileptons. The lepton number of any antilepton
is negative one. So we won’t include any of these in
our answer. We can say then that it’s the muon,
the tau neutrino, and the tauon that all have a lepton number of one.