Neutrino Mass , Proton Decay and Dark Matter in TeV Scale Universal Extra Dimension Models

We show how the problem of small neutrino masses and suppressed proton decay can be simultaneously resolved in 6-D universal extra dimension models (UED) with a low fundamental scale using extended gauge groups that contain the local B − L symmetry. The extra space dimensions are compactified either on a T /Z2 or T /Z2 × Z ′ 2 orbifold depending on whether the full gauge group is SU(2)L×U(1)I3R ×U(1)B−L or SU(2)L×SU(2)R×U(1)B−L. In both cases, neutrino masses are suppressed by an appropriate orbifold parity assignment for the standard model singlet neutrinos and the proton decay rate is suppressed due to a residual discrete symmetry left over from compactification. For lower values of the fundamental scale, a dominant decay mode of the neutron is n → 3ν. An interesting consequence of the model is a possible two component picture for dark matter of the universe.