Fermion number, R-parity and the Majorana neutrino

[Jos Bergervoet]

Can an electron change into a positron if
the neutrino is a Majorana fermion?

An electron emitting a W- could become an
electron-neutrino, which is also an anti-
electron-neutrino and could therefore emit
a second W- to become an anti-electron.

So lepton number changes by 2 (but R-parity
is still conserved). This seems similar to
neutrino-less double-beta decay (depending
on Majorana neutrinos to be possible, I
mean!) Is this correct?

So I'm curious: aren't there a lot of
things that would suddenly be possible
with Majorana neutrinos? (Only neutrino-
less double-beta decay is mentioned,
usually, for some reason..)

--
Jos

[Anon E. Mouse]

I can't speak to the quantum mechanics mechanism you hypothesize. But,
this mechanism if it is demonstrated could account for anomalous
annihilation reactions I observed in a condensed matter experiment
several years ago.

The material was stable in a condensed state, but unstable when
returned to standard conditions. Perhaps super-conduction plays a role
in the mechanism you suppose.

[Jos Bergervoet]

On 7/26/2012 8:34 PM, Anon E. Mouse wrote:
> On Jul 24, 12:43 pm, Jos Bergervoet <jos.bergerv...@xs4all.nl> wrote:

..

>> So I'm curious: aren't there a lot of
>> things that would suddenly be possible
>> with Majorana neutrinos? (Only neutrino-
>> less double-beta decay is mentioned,
>> usually, for some reason..)
>

> I can't speak to the quantum mechanics mechanism you hypothesize. But,
> this mechanism if it is demonstrated could account for anomalous
> annihilation reactions I observed in a condensed matter experiment
> several years ago.

Is it documented?

I did find several other papers about Majorana
fingerprints: (different from neutrino-less
double-beta decay)
http://arxiv.org/abs/hep-ph/0608309
http://arxiv.org/abs/hep-ph/0604064 (hadron collisions)
http://arxiv.org/abs/hep-ph/0512005 (lepton-hadron collisions)

But they all seem to detect only heavy Majorana
neutrinos (10-100GeV range,) so they wouldn't
actually see the 'normal' Majorana neutrinos..

--
Jos

[anticr...@gmail.com]

On Tuesday, July 24, 2012 9:43:30 AM UTC-7, Jos Bergervoet wrote:
> Can an electron change into a positron if
> the neutrino is a Majorana fermion?

If you take the usual neutrinoless double beta decay Feynman diagram,
and rotate one of the electrons into the initial state, it is precisely
a positron turning into an electron. So the answer to your question is
yes.

Electrons are stable however, and charge is conserved, so such a
reaction has to exchange two units of charge with something, like a
nucleus.

An experiment like that is highly impractical though, due to the extreme
weakness of the reaction. It's easier to get a few kilograms of
material (~ 10^26 atoms) and wait for one of them to decay in the
neutrinoless mode.