I know this question has been asked a few times before here in various ways, but I haven't found answers which helped me a lot. For one, the class I am in is not using any of the underlying math, so all the answers about Dirac spinors or Weyl spinors were a bit beyond me. I found this post here, but the top answer still leaves me a bit confused. I have lots of follow-up questions about it, so I thought it might warrant a new post.
When the $W$ boson decays into the fermion and the antineutrino, the antineutrino must be right handed, and it was my understanding that the $W$ boson can only interact with a left-handed muon. But the muon must also be right-handed to satisfy conservation of spin. The resolution to this seems to be that since the muon is not massless, it must have both left-handed and right-handed components, but this doesn't make much sense to me.
To start, given my understanding of helicity, the muon will simply have some helicity, left- or right-handed, which can change based on your frame of reference (since you can boost to change the muons observed motion); and the phrase "left-handed component" doesn't make sense to me. What does it really mean for the $W$ boson to only interact with a left-handed muon, if that property is frame-dependent? What does it mean for a muon to have a left-handed "component", and since we originally decided that the muon must be right handed to conserve spin, how does any left-handed component not still violate spin conservation?