Phenomenological survey of a minimal superstring standard model

Arxiv preprint hep-ph/0703027, 2007

This paper summarizes several developments in string-derived (Minimal Supersymmetric) Standard Models. Part one reviews the first string model containing solely the three generations of the Minimal Supersymmetric Standard Model and a single pair of Higgs as the matter in the observable sector of the low energy effective field theory. This model was constructed by Cleaver, Faraggi, and Nanopoulos in the Z_2 x Z_2 free fermionic formulation of weak coupled heterotic strings. Part two examines a representative collection of string/brane-derived MSSMs that followed. These additional models were obtained from various construction methods, including weak coupled Z_6 heterotic orbifolds, strong coupled heterotic on elliptically fibered Calabi-Yau's, Type IIB orientifolds with magnetic charged branes, and Type IIA orientifolds with intersecting branes (duals of the Type IIB). Phenomenology of the models is compared. In String Theory Research Progress, Ferenc N. Balogh, editor., (ISBN 978-1-60456-075-6), Nova Science Publishers, Inc.}

2013

In the first part of this paper I review the construction of the realistic free fermionic models, as well as current attempts to study aspects of these models in the nonperturbative framework of M– and F–theories. I discuss the recent demonstration of a Minimal Superstring Standard Model, which contains in the observable sector, below the string scale, solely the MSSM charged spectrum, and provides further support to the assertion that the true string vacuum is connected to the Z2×Z2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. In the second part I review the recent formulation of quantum mechanics from an equivalence postulate, which offers a new perspective on the synthesis of gravity and quantum mechanics, and contemplate possible relations with string theory and beyond.

Arxiv preprint hep-th/9604183, 1996

I review how traditional grand unified theories, which require adjoint (or higher representation) Higgs fields for breaking to the standard model, can be contained within string theory. The status (as of January 1996) of the search for stringy free fermionic three generation SO(10) SUSY-GUT models is discussed. Progress in free fermionic classification of both SO(10) 2 charged and uncharged embeddings and in N = 1 spacetime solutions is presented.

1996

I review how traditional grand unified theories, which require adjoint (or higher representation) Higgs fields for breaking to the standard model, can be contained within string theory. The status (as of January 1996) of the search for stringy free fermionic three generation SO(10) SUSY–GUT models is discussed. Progress in free fermionic classification of both SO(10)2 charged and uncharged embeddings and in N = 1 spacetime solutions is presented. Based on talks presented at the Workshop on SUSY Phenomena and SUSY GUTs, Santa Barbara, California, Dec. 7-11, 1995, and at the Orbis Scientiae, Coral Gables, Florida, January 25-28, 1996. To appear in the Proceedings of Orbis Scientiae, 1996. ∗E-mail address: gcleaver@pacific.mps.ohio-state.edu SUSY–GUTs and Strings Elementary particle physics has achieved phenomenal success in recent decades, resulting in the Standard Model (SM), SU(3)C×SU(2)L×U(1)Y, and verification to high precision of many SM predictions. However, many aspects of the ...

2016

For more than two decades, remarkable progress has been made in the construction of supersymmetric Standard Model-like theories from the heterotic string theory. In particular, considerable effort has been invested in studying the abundant phenomenological features of heterotic strings exhibiting N = 1 spacetime supersymmetry. At the same time, their non-supersymmetric counterparts have received little attention on the grounds that strings which do not exhibit spacetime supersymmetry admit large one-loop dilaton tadpoles, and are therefore unstable. Nonetheless, in this epoch of data acquisition from high-luminosity experiments, the observational absence of supersymmetry is striking. Consequently, non-supersymmetric theories receive a profound interest in the particle physics community. In this thesis, a class of non-supersymmetric, tachyon-free, four-dimensional string models is constructed via a string generalisation of Scherk-Schwarz compactification. Such models demonstrate grea...

2015

Over the past three decades, considerable effort has been devoted to studying the rich and diverse phenomenologies of heterotic strings exhibiting spacetime supersymmetry. Unfortunately, during this same period, there has been relatively little work studying the phenomenologies associated with their non-supersymmetric counterparts. The primary reason for this relative lack of attention is the fact that strings without spacetime supersymmetry are generally unstable, exhibiting large one-loop dilaton tadpoles. In this paper, we demonstrate that this hurdle can be overcome in a class of tachyon-free four-dimensional string models realized through coordinate-dependent compactifications. Moreover, as we shall see, it is possible to construct models in this class whose low-lying states resemble the Standard Model (or even potential unified extensions thereof)-all without any light superpartners, and indeed without supersymmetry at any energy scale. The existence of such models thus opens the door to general studies of non-supersymmetric string phenomenology, and in this paper we proceed to discuss a variety of theoretical and phenomenological issues associated with such non-supersymmetric strings. On the theoretical side, we discuss the finiteness properties of such strings, the general characteristics of their mass spectra, the magnitude and behavior of their one-loop cosmological constants, and their interpolation properties. By contrast, on the phenomenological side, the properties we discuss are more model-specific and include their construction techniques, their natural energy scales, their particle and charge assignments, and the magnitudes of their associated Yukawa couplings and scalar masses.

Physics Letters B, 1999

The recent conjecture of possible equivalence between the string scale M S and the minimal supersymmetric standard model unification scale M U ≈ 2.5 × 10 16 GeV is considered in the context of string models. This conjecture suggests that the observable gauge group just below the string scale should be

Physics Letters B, 1992

The unification of gauge couplings in string models is predicted to occur at scales (~ 1018 GeV) which are in disagreement with those obtained, using precise LEP data, in supersymmetric models with minimal matter content (~ 1016 GeV). We present a string-inspired extension of the standard model with one pair of extra vector-like Q and D c representations which allows string unification for D ¢ masses in the few TeV region or less, predicts a light (< 1 TeV) sparticle spectrum which differs from that of the standard supersymmetric model, and allows for adequate radiative electroweak symmetry breaking. The proposed model is the unique minimal choice in this class of extra vector models, it can be embedded most economically in a flipped SU (5) structure, and may be derivable from string.

1998

Introduction CHAPTER 2 2 Compactification on Orbifolds 2.1 Toroidal Compactifications 2.2 General Theory of Orbifold Compactifications 2.3 Duality Symmetries CHAPTER 3 3 Aspects of Threshold Corrections to Low Energy Effective string Theories compactified on Orbifolds 1 where the invariant integral is given by ds 2 = −g µν (x)dx µ dx ν. 2 For n = 0 we have the point particle, for n = 1 we have the string, while for n = 2 we have the membrane and so on. . .. 3 See the footnote following 3.31. 4 Unoriented open and closed strings with N = 1 supersymmetry. 5 The ten dimensional N = 1 supergravity coupled to matter has anomalies coming from hegagon diagrams.

Physics Letters B, 1987

We discuss the communication of supersymmetry breaking from the gravitino mass m3/2 to gaugino masses m~/2, scalar masses mo, and trilinear scalar couplings A in superstring models, assuming that the effective low-energy N= 1, d= 4 supergravity has a modified "no-scale" structure. It is known that rn~/2 ~ 0 at the one-loop level, whilst squared scalar masses m~ vanish at the oneloop level. We analyse a large class of two-loop diagrams, showing that their quadratic divergences cancel and that they contribute 2 4 2