Left-Right Symmetry in 5-D and Neutrino Mass in TeV-scale Gravity Models

We construct a left-right symmetric model based on the gauge group SU(2)L × SU(2)R × U(1)B−L in five dimensions where both the gauge bosons and fermions reside in all five dimensions. The orbifold boundary conditions are used not only to break the gauge symmetry down to SU(2)L × U(1)Y × U(1)Y ′ but also to “project” the right handed neutrino out of the zero mode part of the spectrum, providing a new way to understand the small neutrino masses without adding (singlet) bulk neutrinos. This formulation of the left-right model has also two new features: (i) it avoids most existing phenomenological bounds on the scale of the right handed WR boson allowing for the possibility that the right handed gauge bosons could have masses under a TeV, and (ii) it predicts a stable hadron or lepton with mass of order of the inverse radius of the fifth dimension.