Lorentz violating extension of the Standard Model and the Beta-decay   end-point
  The Standard Model extension with additional Lorentz violating terms allows for redefining the equation of motion of a propagating left-handed fermionic particle. The obtained Dirac-type equation can be embedded in a generalized Lorentz-invariance preserving-algebra through the definition of Lorentz algebra-like generators with a light-like preferred axis. The resulting modification to the fermionic equation of motion introduces some novel ingredients to the phenomenological analysis of the cross section of the tritium $\beta$-decay. Assuming lepton number conservation, our formalism provides a natural explanation for the tritium $\beta$-decay end-point via an effective neutrino mass term without the need of a sterile right-handed state. 
Alex E. Bernardini, O. Bertolami