The Neutrino Minimal Standar Model (nuMSM or
MSM) is an extension of the
Standard Model with three
right-handed (or sterile) neutrinos. It aims to address within one consistent framework several
problems beyond the Standard Model
The Lagrangian of the
MSM is
Here
are new Yukawa couplings,
are left-handed leptonic doublets, the index
labels generations,
is a Higgs doublet with
. The right-handed neutrinos
have zero electric, weak and strong charges. The
Majorana masses are consistent with the gauge symmetries of the SM This is the
see-saw Lagrangian, however the Majorana masses of the right-handed neutrinos are chosen to be below electroweak scale. The smallness of the neutrino masses is achieved via small Yukawa couplings.
See references
[1, 2] for the original paper and
[3] for the recent review
References:- [1]^ T. Asaka and M. Shaposhnikov The nuMSM, dark matter and baryon asymmetry of the universe, Phys. Lett. B620:17-26 (2005) INSPIRE
- [2]^ T. Asaka, S. Blanchet and M. Shaposhnikov The nuMSM, dark matter and neutrino masses, Phys. Lett. B631:151-156 (2005) INSPIRE
- [3]^ A. Boyarsky, O. Ruchayskiy and M. Shaposhnikov, Ann. Rev. Nucl. Part. Sci. 59 (2009) 191 [arXiv:0901.0011]. INSPIRE