The gauge singlet right-handed neutrinos are one of the essential fields in neutrino mass models that explain tiny masses of active neutrinos.
If you feel the need to create right handed neutrinos (with masses different from any of the three Standard Model active neutrinos) to explain anything, your model is probably wrong because you are too lazy to find a solution that doesn't need them, and there is no positive experimental evidence that they exist. This possibility has been a perennial source for a steady stream of dead end theoretical speculation for at least a decade or two. This paper is the work of dim bulbs in the physics community. Try harder until you come up with something better.
To be clear, I'm not saying that I'm a professional physicist coming up with something better myself. But you don't have to be a genius composer yourself to appreciate the difference between Mozart and a mediocre music theory student.