# What is the diference between right handed neutrinos And quarks?

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1. Mar 17, 2013

### the_pulp

In the traditional Standard Model, Why right handed quarks can have mass And there cant be any right handed neutrino? Wikipedia says that it damages renormalizability, but why does that not happen with the corresponding quarks?
In other words, why did you invent the see saw mechanism for massive neutrinos while you have not done that for massive quarks?
Perhaps I did not formulate the question in rigurous words, but I think that you may understand what I'm trying to know?

2. Mar 18, 2013

### ofirg

Its seems that you are mixing two things:

1.) neutrinos in the SM vs quarks in the SM

Strictly speaking, neutrinos in the SM are massless while quarks can be massive, because there are no right handed neutrinos while there are right handed quarks.

2.) right handed neutrinos vs right handed quarks

The standard model can be extended to include right handed neutrinos ( a popular extension in order to give neutrinos mass)

The main difference from right handed neutrinos and right handed quarks is that right handed neutrinos have no conserved charge, and therefore can be given mass without the left handed neutrinos and without the higgs mechanism.

Therefore there mass is expected to be much larger since it is not proportional to the electroweak symmetry breaking scale.

the see saw mechanism is based on the fact that
heavy right handed neutrinos+ small masses that mix left and right

produces three very light mass eigenstates ( and three heavy ones)

and used to explain the smallness of neutrino masses compared to other fermions in the SM.

These are of course all models. No one knows for sure the physics behind neutrino masses

3. Mar 18, 2013

### the_pulp

Ok, few words but very clear. Do you know any paper which describes this trivial extension (I sort of imagine it, but it is better to see it written)

Sorry, I didnt get that idea. Are you trying to say that, because of neutrino oscillations the mass of the right handed neutrinos should be small so, as a consequence, there should be a mechanism that makes these masses naturally small? If not, I would appreciate if you can describe it a bit more (or perhaps if you can give me some reference)

Thanks for all!

4. Mar 18, 2013