Related papers: A Light Z' Heterotic-String Derived Model
We discuss the construction of heterotic--string models that allow for the existence of an extra $Z^\prime$ at low scales. One of the main difficulties encountered is that the desired symmetries tend to be anomalous in the prevailing three…
We explore the phenomenological viability of a light Z' in heterotic-string models, whose existence has been motivated by proton stability arguments. A class of quasi-realistic string models that produce such a viable Z' are the Left-Right…
The dark matter issue is among the most perplexing in contemporary physics. The problem is more enigmatic due to the wide range of possible solutions, ranging from the ultra-light to the super-massive. String theory gives rise to plausible…
The discovery of the Higgs boson at the LHC supports the hypothesis that the Standard Model provides an effective parameterisation of all subatomic experimental data up to the Planck scale. String theory, which provides a viable…
Recently it was demonstrated that free fermionic heterotic-strings can produce models with solely the Minimal Supersymmetric Standard Model states in the low energy spectrum. This unprecedented result provides further strong evidence for…
The MiniBooNE collaboration found evidence for the existence of sterile neutrinos, at a mass scale comparable to the active left-handed neutrinos. While sterile neutrinos arise naturally in large volume string scenarios, they are more…
The Standard Model indicates the realization of grand unified structures in nature, and can only be viewed as an effective theory below a higher energy cutoff. While the renormalizable Standard Model forbids proton decay mediating operators…
Grand unification, and its incarnation in the form of heterotic-string unification, are the only extensions of the Standard Model that are rooted in the structure of the Standard Model itself. In this context, it was proposed that the…
Proton stability is one of the most perplexing puzzles in particle physics. While the renormalizable Standard Model forbids proton decay mediating operators due to accidental global symmetries, many of its extensions introduce such…
We present a novel string-derived $U(1)$ combination that satisfies necessary properties to survive to low scales. We discuss previous attempts at acquiring such an abelian gauge symmetry from two different string embeddings and the…
We investigate the cosmological constraints on exotic stable matter states which arise in realistic free fermionic superstring models. These states appear in the superstring models due to a ``Wilson--line'' breaking of the unifying…
In the four dimensional free fermionic formulation of the heterotic string, a semi-realistic $SU(4)\times SU(2)_L \times SU(2)_R$ model is proposed with three fermion generations in $(4,2,1)+(\bar 4,1,2)$ representations. The gauge symmetry…
With the apparent discovery of the Higgs boson, the Standard Model has been confirmed as the theory accounting for all sub-atomic phenomena. This observation lends further credence to the perturbative unification in Grand Unified Theories…
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…
Many extensions of the standard model, especially grand unified theories and superstring models, predict the existence of additional Z' bosons and associated exotic chiral supermultiplets. It has recently been argued that for classes of…
Conventional superstring derived E$_6$ models can accommodate small neutrino masses if a discrete symmetry is imposed which forbids tree level Dirac neutrino masses but allows for radiative mass generation. Since the only possible…
Potentially realistic string models often contain additional abelian gauge factors besides the standard model group. The consequences of such extended gauge structure are manifold both for theory and phenomenology as I show focussing in the…
The ATLAS collaboration recently recorded possible excess in the di--boson production at the di--boson invariant mass at around 2 TeV. Such an excess may be produced if there exist additional $Z^\prime$ and/or $W^\prime$ at that scale. We…
Chiral representations are the key in obtaining light fermions from some ultra-violet completed theories. The well-known chiral example is one family set of fifteen chiral fields in the standard model. We find a new chiral theory…
This thesis is the discussion of heterotic and type I string phenomenology. The heterotic string model is based on the free--fermionic formalism. This is the first case where non--Abelian VEV's, as opposed to singlet VEV's are required for…