Gauge Origin of Baryon Number Conservation and Suppressed Neutrino Masses From Five Dimensions

We consider a 5D SUSY $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y\times \mathcal{U}(1)$ model compactified on an $S^{(1)}\mathrm{/}{Z}_2$ orbifold. To cancel anomalies arising from the presence of $\mathcal{U}(1)$, we employ a Chern-Simons term and also chiral fields which could reside on the brane or in the bulk depending on the model. The presence of $\mathcal{U}(1)$ symmetry leads to baryon number conservation, gives rise to matter parity, and permits satisfactory neutrino masses and mixings even for a low fundamental scale. The brane Fayet-Iliopoulos D-terms naturally break $\mathcal{U}(1)$, leaving N=1 SUSY unbroken in 4 dimensions.