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What exactly are anti-neutrinos?

by Yashbhatt
Tags: antineutrinos
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Yashbhatt
#1
May5-14, 12:49 PM
P: 174
According to the the definition of anti-particles, they are particles with same mass but opposite charge. Neutrinos by definition have no charge. So, how can it have an anti-particle?
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jedishrfu
#2
May5-14, 12:56 PM
P: 2,974
Wikipedia has a brief description:

http://en.wikipedia.org/wiki/Anti-ne...#Antineutrinos

They come out of beta particle decay. So if the beta particles is an electron then you see anti-neutrinos and if the beta particle is a positron then you see neutrinos.

http://en.wikipedia.org/wiki/Beta_decay

Its possible though not proven that they are in fact the same particle (aka Majorana particle)
Bill_K
#3
May5-14, 01:27 PM
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Quote Quote by Yashbhatt View Post
According to the the definition of anti-particles, they are particles with same mass but opposite charge.
This is true, but not a complete definition. There are several different things called "charge", and the antiparticle has the opposite value for each.

Gluons, for example, although they have zero electric charge, they also carry color charge, and so a gluon and its antiparticle have opposite color charge.

Likewise there are neutral K-mesons K0 and K0-bar which carry opposite strangeness.

Yashbhatt
#4
May5-14, 01:40 PM
P: 174
What exactly are anti-neutrinos?

So, can we have something like anti-neutron?
jedishrfu
#5
May5-14, 01:45 PM
P: 2,974
Quote Quote by Yashbhatt View Post
So, can we have something like anti-neutron?
Yes.

http://en.wikipedia.org/wiki/Anti-neutron
Yashbhatt
#6
May5-14, 01:51 PM
P: 174
Thanks. I did not google anti-neutrino before posting.
craigi
#7
May6-14, 03:58 AM
P: 421
Quote Quote by Yashbhatt View Post
Thanks. I did not google anti-neutrino before posting.
There's some confusion here. A neutrino and a neutron aren't the same thing.
Yashbhatt
#8
May6-14, 03:59 AM
P: 174
Sorry, I meant anti-neutron.
ChrisVer
#9
May6-14, 04:53 AM
P: 895
Apart from all, there are studies which propose that the neutrino and antineutrino are the same particle... Those studies consider the neutrino as a Majorana particle (and that's something only neutrally charged particles can be)... That search is based in observing neutrinoless double beta decay.... Unfortunately, we haven't been able to verify that nature so far...
Yashbhatt
#10
May6-14, 05:41 AM
P: 174
But I think there are arguments against it being a Majorana partcile. See http://physics.stackexchange.com/que...-anti-neutrino
Bill_K
#11
May6-14, 06:41 AM
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Quote Quote by Yashbhatt View Post
But I think there are arguments against it being a Majorana partcile. See http://physics.stackexchange.com/que...-anti-neutrino
Is he citing evidence against Majorana neutrinos, or evidence against leptogenesis? And how strong is it? If I were you, I'd ask the responder for the specific reference.
Vanadium 50
#12
May6-14, 07:06 AM
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Stackexchange is not a valid source.
Yashbhatt
#13
May6-14, 08:10 AM
P: 174
Why?
jim mcnamara
#14
May6-14, 09:41 AM
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On stackexchange, like here at PF, anyone can post. Stackexchange depends on a different method of controlling posts by people who are expounding personal research or pet theories. They hope someone in the community will correct the off-the-mark post. PF depends on physicists, who try to remove crackpot posts. And there is active correction. Bill K is being polite. "rob" is expounding what appears to be a pet theory. Note that he has about 640 "status points". The point system is supposed to let you in on the believable-ness of the poster in general.
Yashbhatt
#15
May6-14, 10:19 AM
P: 174
Ok. I get what you say. I just mentioned the link because I found a more detailed answer there.
phinds
#16
May6-14, 11:54 AM
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Quote Quote by Yashbhatt View Post
Ok. I get what you say. I just mentioned the link because I found a more detailed answer there.
"detailed" does not necessarily have anything to do with "correct". Check your sources. There's a list here at PF for those that are good/bad.
ChrisVer
#17
May6-14, 11:55 AM
P: 895
I never said that neutrinos are Majorana particles... What I said is that there is a lot of work being done in studying that theory and confirming it... and as I pointed out, experiments have been fruitless until now (equivalently said, there's not been experimental verification of physics beyond the Standard Model, only indirect signs). If we verify the neutrinoless double beta decay, there will be a problem with the accidental symmetries of Baryon and Lepton numbers (they will be violated) which appears in the Standard Model.
The big thing is the difficulties in measuring that experimentally (as neutrinos have always been), the rarity of the events (ordinary double beta decay is very slow itself) and of course the clearness of the subject material and "technology" .
Orodruin
#18
May6-14, 03:02 PM
P: 539
Neutrino oscillations in themselves are an observation of physics beyond the Standard Model since lepton flavor is conserved in the SM. (Gravity also seems to be a fairly established observation of BSM physics.) Furthermore, B and L are not separate accidental symmetries of the Standard Model but B+L may be violated through non-perturbative effects. Anyway, breaking B-L would be good news for the possibility of generating the baryon asymmetry of the Universe.


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