Re: C, P, T and neutrino mass

From: David Hillman (dhi_at_cablespeed.com)
Date: 02/14/05 

Date: Mon, 14 Feb 2005 20:34:47 +0000 (UTC)

Here is what confuses me. Say you have an atom with a given chirality
and it does beta decay. My understanding is, this beta decay always goes
in some particular direction, following say a left-hand rule involving
spin and the sign of the momentum. Now look at the same scene from a new
Lorentz frame in which the atom is at rest. Which direction does the
beta decay go in?

Dallas Kennedy wrote:
> Neutrino mass violates a chiral symmetry and/or lepton number. It's not an
> experimental issue, but how all the experimental data fir together at the
> theoretical level.
>
> Careful not to confuse chirality and parity. Chiral symmetry is violated by
> any fermion mass. Parity is violated only when some force (like the weak
> force) doesn't treat L and R fermion chiralities *equally*. It has nothing
> to do with mass.
>
> Any particle with mass can be brought to a stop (that is, has a rest frame).
> If you stop and then reverse a fermion's direction, its chirality does
> change. Its spin direction remains the same, but its momentum changes sign.
>
> Parity conservation is still violated, not by a neutrino in isolation, but
> when it weakly interacts with other particles. Weak parity violation has
> nothing to do with neutrino mass, but is a feature of the weak gauge field
> coupling to fermions.
>
> "David Hillman" <dhi@cablespeed.com> wrote in message
> news:xY6dnTelp5xgrpjfRVn-jA@cablespeedwa.com...
>
>>I'm wondering what your thoughts are about symmetry violations in light
>>of neutrino mass.
>>
>>I think I read someplace that if neutrinos have mass then there is some
>>Lorentz frame in which a right-handed neutrino becomes a left-handed
>>neutrino. Is that true? If so, what does that say about parity
>>violation, which used to seem like a 100% symmetry violation?
>>
>>Are there experiments underway that might shed some light on this?
>
>

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