# Anti nutrinos

1. Apr 8, 2005

### benzun_1999

hi,

What are anti-nutrinos? what are their properties.
i know what is an nutrino but an anti nutrino looks confusing.

-Benzun

2. Apr 8, 2005

### marlon

Tne anti-neutrino is the neutrino's anti-particle just like the electron and the positron. An anti-particle has opposite quantum-properties like charge, helicity and so on...

Neutrino's don't have charge and they have a very very small mass. they were postulated because so that beta decay would respect energy conservation. Given the zero charge and small mass they 'hardly' interact with matter around them, which makes it very difficult to detect them.

the most striking difference between the neutrino and it's anti-particle is the helicity or handedness. this site explains it :

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino3.html#c1

Keep in mind that there are several types of neutrino's, of which the electron (anti)-neutrino (the one from beta decay)is the 'most famous'

Here is more on neutrino's : http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html#c1
marlon

3. Apr 8, 2005

### mathman

There is an open question concerning neutrinos and anti-neutrinos. Specifically, are they the same or not?

4. Apr 8, 2005

### marlon

No they are not. Not all physical quanities that define such particles are the same. Just look at their helicity. But then again what about behaviour under interactions ?

marlon

5. Apr 8, 2005

### Meir Achuz

High Energy Physics - Phenomenology, abstract
hep-ph/0504052
From: Boris Kayser [view email]
Date: Thu, 7 Apr 2005 01:13:06 GMT (34kb)

Neutrino Intrinsic Properties: The Neutrino-Antineutrino Relation
Authors: Boris Kayser
Comments: 9 Pages, 3 figures; Nobel Symposium on Neutrino Physics

Are neutrinos their own antiparticles? We explain why they very well might be. Then, after highlighting the fact that, to determine experimentally whether they are or not, one must overcome the smallness of neutrino masses, we discuss the one approach that nevertheless shows great promise. Finally, we turn to the consequences of neutrinos being their own antiparticles. These consequences include unusual electromagnetic properties, and manifestly CP-violating effects from Majorana'' phases that have no quark analogu

6. Apr 9, 2005

### Haelfix

The smallness of the neutrino mass could be given rather trivially by the seesaw mechanism... Typically this is done in the context of a small Majorana mass term. If you don't like that, just add an adhoc right handed Dirac or Majorana neutrino species and finetune away.

As to being their own antiparticle, thats more or less ruled out by experiment now.

7. Apr 10, 2005

### benzun_1999

Thanks morlon. The link u gave was very helpful. can any one just explain hellicity a bit clearly. is it direction of momentum of a particle with respect to spin?

8. Apr 10, 2005

### marlon

yes it is

marlon

9. Apr 10, 2005

### dextercioby

Nope,it is the projection of the total angular momentum on the direction of the momentum...

Daniel.

10. Apr 11, 2005

### marlon

spin is angular momentum dexter, don't start whining...

to the OP : you are correct : The relative orientations of spin and linear momentum .

marlon