New Standard Model Vacua from Intersecting Branes

We construct new D6-brane model vacua (non-supersymmetric) that have at lowenergy exactly the standard model spectrum (with right handed neutrinos). Theminimal version of these models requires five stacks of branes. and theconstruction is based on D6-branes intersecting at angles in $D = 4$ typetoroidal orientifolds of type I strings. Three U(1)'s become massive throughtheir couplings to RR couplings and from the two surviving anomaly free U(1)'s,one is the standard model hypercharge generator while the extra anomaly freeU(1) could be broken from its non-zero couplings to RR fields and also bytriggering a vev to previously massive particles. We suggest that extramassless U(1)'s should be broken by requiring some intersection to respect N=1supersymmetry thus supporting the appearance of massless charged singlets atthe supersymmetric intersection. Proton is stable as baryon number is gaugedand its anomalies are cancelled through a generalized Green-Schwarz mechanism.Neutrinos are of Dirac type with small masses, as in the four stack standardmodels of hep-th/0105155, as a result of the existence of a similar PQlike-symmetry. The models are unique in the sense that they predict theexistence of only one supersymmetric particle, the superpartner of $\nu_R$.Comment: 32 pages, 1 figure, LaTex, typos correcte