Standard Model Compactifications of IIA Z3 x Z3 Orientifolds from Intersecting D6-branes

Abstract

We discuss the construction of chiral four dimensional ${\mathbf{T}}^6/({\mathbf{Z}}_3\times {\mathbf{Z}}_3)$ orientifold compactifications of IIA theory, using D6-branes intersecting at angles and not aligned with the orientifold O6 planes. Cancellation of mixed U(1) anomalies requires the presence of a generalized Green-Schwarz mechanism mediated by RR partners of closed string untwisted moduli. In this respect we describe the appearance of three quark and lepton family $SU(3{)}_C\times SU(2{)}_L\times U(1{)}_Y$ non-supersymmetric orientifold models with only the massless spectrum of the SM at low energy that can have either no exotics present and three families of ${\nu }_R$'s (A${}^{\prime }$-model class) or the massless fermion spectrum of the N=1 SM with a small number of massive non-chiral colour exotics and in one case with extra families of ${\nu }_R$'s (B${}^{\prime }$-model class). Moreover we discuss the construction of SU(5), flipped SU(5) and Pati-Salam $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$ GUTS - the latter also derived from adjoint breaking - with only the SM at low energy. Some phenomenological features of these models are also briefly discussed. All models are constructed with the Weinberg angle to be 3/8 at the string scale.

Comments: 31 pages, 1 figure; v2: typos corrected, comments in the introduction added v3:35 pages, Pati-Salam G422 models & comments on split susy scenario and refs added; to appear in NPB