I Right Handed Neutrinos/Heavy Neutral Leptons

[Trixie Mattel]

When are right handed neutrinos considered to be heavy neutral leptons (HNL).

For instance are the RH neutrinos in the vMSM HNL?
Are the RH neutrinos in the Left-Right extensions of the standard model HNL?Thank you

 

[Buzz Bloom]

Hi Trixie:

I am surprised that no one has so far responded to your question. I am certainly very far from being an expert, but I have been interested in the possibility that RH Neutrinos might be (most of) dark matter. I was not familiar with the abbreviations vMSM but found the following.

http://www-thphys.physics.ox.ac.uk/people/KyleAllison/vmsm.html
​

There was a discussion in another thread implying a minimum mass for such particles based on the fact that if the particles were too light, it would change known observations.

https://www.physicsforums.com/threads/q-re-the-matter-term-in-friedmanns-equation.903173​

Here are some quotes from a post by @Chalnoth.

Neutrinos as a significant component of the dark matter are definitely out, as they are way too light, and wouldn't be able to form structures early enough in the universe to explain observations.​

As for the possibility of kinetic energy, yes, it's absolutely conceivable that the dark matter has a temperature in our early universe that is measurably different from zero. This is contained in the proposed "warm dark matter" models. These models don't currently have much in the way of supporting evidence, but many are plausible.​

Regards,
Buzz