Right-Handed Neutrinos: Interactions & Weight Explained

[bsaucer]

I've read that if right-handed neutrinos exist, they should be heavier than left-handed neutrinos (why?). I figured if an observer moves faster than a left-handed neutrino, he'd see it as right-handed. Also, would right-handed neutrinos interact with Z-bosons? How would such interactions be detected?

 

[Orodruin]

I've read that if right-handed neutrinos exist, they should be heavier than left-handed neutrinos (why?).

Right handed neutrinos are standard model singlets. As soon as you add them to your model, there is nothing stopping you from writing down a Majorana mass term for them. A priori, you have no handle on what this mass should be - it is a new scale in your theory. To put it very large is popular for several reasons, among them explaining the light masses of neutrinos through the seesaw mechanism, but by no means is this a necessary requirement.

I figured if an observer moves faster than a left-handed neutrino, he'd see it as right-handed.

This is quite a bit of over-simplification. Suffice to say, if you do this for a Majorana neutrino, you will obtain a right handed anti-neutrino.

Also, would right-handed neutrinos interact with Z-bosons? How would such interactions be detected?

No. However, since there would be an ever so small mixing with the light neutrinos due to the Yukawa term, the actual physical state with definite mass will have a Z interaction suppressed by the mixing squared. The interaction with the W, or with the Z and a light neutrino, would be linearly suppressed by the mixing and cause decays of the heavy states. This is the main mechanism behind leptogenesis, which is a proposed solution to the baryon asymmetry.

In order to test the interactions of the right handed neutrinos directly, you would have to produce them. This is far beyond current experimental limits for most viable models.