0

I am a bit confused about Majorana neutrinos. A generic Dirac spinor can be written in terms of his left and right-chiral components as $$ \psi = \begin{pmatrix} \psi_L \\ \psi_R \end{pmatrix} $$ A Majorana neutrino is a fermion for which the two components are not independent but related through charge conjugation. It seems to me that there are two kinds of Majorana neutrinos that could be part of the standard model:

  1. a Majorana neutrino that looks like $$ \nu = \begin{pmatrix} \nu_L \\ \nu_L^c \end{pmatrix} $$ this neutrino is 'SU(2) charged' and if we want to add such a neutrino with a mass term to the standard model we need a dimension 5 operator
  2. a Majorana neutrino that looks like $$ N = \begin{pmatrix} N_R^c \\ N_R \end{pmatrix} $$ this is a completely sterile neutrino, it has no charge at all. As such, we can add it to the standard model even with a mass term without breaking gauge invariance.

Is my understanding correct? These kinds of neutrinos may be both present in some beyond standard model theories, but what I want to understand is: are active and sterile Majorana neutrinos two different things?

Qmechanic
  • 201,751
Crucio
  • 131
  • 1
    Linked. – Cosmas Zachos Oct 07 '23 at 16:07
  • 2
    It might help you to completely eschew the term "Majorana neutrino", which confuses you, and instead, discuss Majorana masses and lepton number violation, as one does in the see-saw mechanism. Indeed, both active and sterile neutrinos may have Majorana mass terms, the former through the Weinberg term. – Cosmas Zachos Oct 07 '23 at 16:12
  • Also see @CosmasZachos very illuminating comments and answer here : https://physics.stackexchange.com/questions/429292/why-is-the-notion-of-neutrinos-as-possiblly-majorana-fermions-still-promoted-giv – MadMax Oct 09 '23 at 14:20

0 Answers0