Towards String Predictions

Abstract

The aim of superstring phenomenology is to develop the tools and methodology needed to confront string theory with experimental data. The first mandatory task is to find string solutions which reproduce the observable data. The subsequent goal is to extract potential signatures beyond the observable data. Recently, by studying exact flat directions of non-Abelian singlet fields, we demonstrated the existence of free fermionic heterotic-string models in which the $SU(3)\times SU(2)\times U(1{)}_Y$-charged matter spectrum, just below the string scale, consists solely of the MSSM spectrum. In this paper we study the possibility that the exact flat directions leave a $U(1{)}_{Z^{\prime }}$ symmetry unbroken at the Planck scale. We demonstrate in a specific example that such unbroken $U(1{)}_{Z^{\prime }}$ is in general expected to be not of the GUT type but of intrinsic stringy origin. We study its phenomenological characteristics and the consequences in the case that $U(1{)}_{Z^{\prime }}$ remains unbroken down to low energies. We suggest that observation in forthcoming colliders of a $Z^{\prime }$, with universal couplings for the two light generations but different couplings for the heavy generation may provide evidence for the $Z_2\times Z_2$ orbifold which underlies the free fermionic models.

18 pages. Standard Latex. References added

References in corpus (4)

• Indications for an Extra Neutral Gauge Boson in Electroweak Precision Data
• A Minimal Superstring Standard Model II: A Phenomenological Study
• A Minimal Superstring Standard Model I: Flat Directions
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• The impact of lepton-flavor violating Z' bosons on muon g-2 and other muon observables
• String Inspired Neutrino Mass Textures in Light of KamLAND and WMAP
• Extra $Z^{\prime }$s and $W^{\prime }$s in Heterotic--String Derived Models
• On the Possibility of Optical Unification in Heterotic Strings
• Stringent Phenomenological Investigation into Heterotic String Optical Unification
• D-term challenges for supersymmetric gauged abelian flavor symmetries
• The LHC di-photon excess and Gauge Coupling Unification in Extra $Z^{\prime }$ Heterotic-String Derived Models
• Note on a NAHE Variation
• Minimal Superstring Standard Model: A Review
• Observable/Hidden Broken Symmetry for Symmetric Boundary Conditions
• Continuation of the Fermion-Number Operator and the Puzzle of Families