Puzzling Lefthanded Neutrinos in Beta-Decay

[ulf.horsing]

I am puzzled by the "always lefthanded" neutrinos. In the beta-decay process a W-boson decays to an electron and an anti-neutrino, which must have same spin direction in order to comply with spin conservation. In the deay of a pion to a muon and an anti-muon neutrino these two particles must have opposite spin of the same reason. One may measure spin of electrons and muons but the spin of neutrinos can only be determined indirectly. Apparently this gives always lefthanded neutrinos, but how can you generalize from that to all neutrinos being lefthanded? Is it not possible for neutrinos to be produced in other rections than the beta-decay?

 

[diazona]

Not as far as we know. All experimental and theoretical evidence to date suggests that neutrinos have no electromagnetic charge and no color charge, so they're not subject to the strong or electromagnetic force. All that's left is the weak force, which is the force responsible for beta decay and similar reactions. So yes, there is only that one way to produce neutrinos.

 

[sir-pinski]

The concept of "left-handed" and "right-handed" neutrinos can be confusing, as it is based on the direction of spin of the particle rather than its physical orientation. In the case of beta-decay, the W-boson decays into an electron and an anti-neutrino, both of which must have the same spin direction in order to conserve angular momentum. This is why we observe "always left-handed" neutrinos in this process.

Additionally, in the decay of a pion to a muon and an anti-muon neutrino, the two particles must have opposite spin directions in order to conserve angular momentum. This is why we observe "always left-handed" neutrinos in this process as well.

However, it is important to note that this does not mean that all neutrinos are always left-handed in every situation. Neutrinos can be produced in other reactions besides beta-decay, and in these cases, their spin direction may differ. It is the specific process of beta-decay and pion decay that leads to the observation of "always left-handed" neutrinos.

Furthermore, the spin of neutrinos can only be indirectly determined, making it difficult to directly observe their spin direction. This is why we rely on the principles of spin conservation to understand the spin behavior of neutrinos in these processes.

Overall, while it may seem puzzling that we only observe "always left-handed" neutrinos in beta-decay and pion decay, it is important to remember that this is a result of the specific processes and conservation laws involved. It does not necessarily mean that all neutrinos are always left-handed in every situation.