= Matter parity allows Majorana neutrino masses
{title2=$P_M(N_iN_j)=+1$}
<Matter parity> assigns $-1$ to every matter <chiral superfield>, including a singlet $N$ describing a conjugate <right-handed neutrino>, and $+1$ to Higgs <chiral superfields>. Thus the quadratic <superpotential> term $\frac12M_{ij}N_iN_j$ is even, although it changes <lepton number> by two. The higher-degree operators $QQQL$ and $(LH_u)^2$ are also even and violate <baryon number> or <lepton number>. Exact <R-parity> therefore forbids the renormalizable trilinear violations $LLE$, $LQD$, $UDD$, $NH_dH_u$, $NNN$, but does not imply conservation of these continuous charges in every allowed interaction.
Back to article page
