PT Journal
AU Aparici, A
   Herrero-Garcia, J
   Rius, N
   Santamaria, A
TI On the nature of the fourth generation neutrino and its implications
SO Journal of High Energy Physics
JI J. High Energy Phys.
PY 2012
BP 030
EP 31pp
VL 07
IS 7
DI 10.1007/JHEP07(2012)030
LA English
DE Beyond Standard Model; Neutrino Physics
AB We consider the neutrino sector of a Standard Model with four generations. While the three light neutrinos can obtain their masses from a variety of mechanisms with or without new neutral fermions, fourth-generation neutrinos need at least one new relatively light right-handed neutrino. If lepton number is not conserved this neutrino must have a Majorana mass term whose size depends on the underlying mechanism for lepton number violation. Majorana masses for the fourth-generation neutrinos induce relative large two-loop contributions to the light neutrino masses which could be even larger than the cosmological bounds. This sets strong limits on the mass parameters and mixings of the fourth-generation neutrinos.
ER