Higgs mechanism in heterotic orbifolds

Abstract

We study spontaneous gauge symmetry breaking in the framework of orbifold compactifcations of heterotic string theory. In particular we investigate the electroweak symmetry breakdown via the Higgs mechanism. Such a breakdown can be achieved by continuous Wilson lines. Exploiting the geometrical properties of this scheme we develop a new technique which simplifies the analysis used in previous discussions.

Can string theory predict the Weinberg angle?

“…In Georgi-Glashow SU(5) [11], U1 Y is obtained as the Abelian factor that is left over after breaking SU(5) to the standard model 1 In (heterotic) orbifold constructions, U(1) factors may be broken by the mechanism of continuous Wilson lines, as explored in Refs. [9,10]. 2 All the additional particles that are not in the MSSM are termed exotics.…”

“…3). The first step in the analysis was a judicious choice of a shift vector leading to either SO (10) or E 6 , with the additional requirement that at least one family representation, 16 or 27, respectively, be localized in the first twisted sector. Wilson lines subsequently broke the gauge symmetry to that of the standard model and hypercharge was realized as the U(1) which lies in SU(5), cf.…”

“…Of the (i) 21 841 models, (ii) 33% contain the SM gauge group in at least one E 8 , (iii) 16% contain the SM gauge group as a subset of SO(10), (iv) 5% are three-generation standard models (w.r.t. color and weak isospin) lying in SO (10), and (v) 0.6% are three-generation standard models (now including hypercharge) with a vectorlike spectrum where hypercharge is that of GeorgiGlashow SU5 SO10. 3 The SO(10) structure was required not only for hypercharge, but also for a couple of other reasons, such as gauge and Yukawa coupling unification, the presence of a B ÿ L symmetry, a discrete subgroup of which may be a candidate for R-parity, etc.…”

“…To that end, we considered 3563 models whose gauge symmetries contained SU3 SU2 as a subgroup of SO (10). Of this set, 1170 models had a three-generation spectrum w.r.t.…”

“…Then in the first twisted sector (see Fig. 1) it was shown that massless chiral multiplets in the 27 of E 6 or 16 of SO (10) exist, residing at ''local'' GUT twisted sector fixed points. In fact, with one Wilson line lying in the SO(4) torus, there are exactly two possible families of quarks and leptons.…”