P-violation experiment

1. May 28, 2006

Lucretius

I just finished reading a book, The Quantum World, but have gone back and looked at some interesting and confusing parts again. One involving P-violation I cannot understand for the life of me and was hoping someone would help me be able to.

The author discussed an experiment by Leon Lederman and others, where they produced positive pion particles in a cyclotron. This particle subsequently decayed into a positive muon and it's neutrino form. The muon is experimentally shown to always be single-handed. The neutrino is of the same left-handedness as the muon.

This next part is what confuses me. He says that "if parity were conserved, half of the neutrinos created would be left-handed and half would be right-handed. Experiment indicates that they all were single-handed (meaniung that parity conservation is as totally violated as it could be!)

I don't get it. If the muon is experimentally shown to be single-handed, why is it a problem that it's neutrino is? Am I reading this wrong? Can the positive muon be both left and right-handed, but the neutrino is only left-handed, and that's the P-violation? I'd like to understand this experiment and it's conclusion of P-violation, but I simply don't with the wording given.

2. May 28, 2006

Norman

http://ccreweb.org/documents/parity/parity.html
I was unablet to figure out (not on campus- so no access to online articles) which was the correct paper for the Lederman experiment. But a simple search on scholar.google.com should be able to allow you to track down the original article which should clear up any questions you have.
Cheers,
Ryan

3. May 29, 2006

Meir Achuz

If P were conserved, both the mu and the neutrino would have equally rlght and left helicity. Since the pion has spin zero, if the neutrino has only L helicity (violation of P), the muon must also have L helicity.
They talk about measuriing the helicity of the muon, because that is easier to do than for the neutrino.