Fourth Generation Majorana Neutrinos

Understand

We investigate the possibility of a fourth sequential generation in the lepton sector.

• Assuming neutrinos to be Majorana particles and starting from a recent - albeit weak - evidence for a non-zero admixture of a fourth generation neutrino from fits to weak lepton and meson decays we discuss constraints from neutrinoless double beta decay, radiative lepton decay and like-sign dilepton production at hadron colliders.
• Also an idea for fourth generation neutrino mass model building is briefly outlined.
• Here we soften the large hierarchy of the neutrino masses within an extradimensional model that locates each generation on different lepton number violating branes without large hierarchies.