A Minimal Superstring Standard Model II: A Phenomenological Study

Recently, we demonstrated the existence of heterotic--string solutions in which the observable sector effective field theory just below the string scale reduces to that of the MSSM, with the standard observable gauge group being just SU(3)_C x SU(2)_L x U(1)_Y and the SU(3)_C x SU(2)_L x U(1)_Y-charged spectrum of the observable sector consisting solely of the MSSM spectrum. Associated with this model is a set of distinct flat directions of vacuum expectation values (VEVs) of non-Abelian singlet fields that all produce solely the MSSM spectrum. In this paper, we study the effective superpotential induced by these choices of flat directions. We investigate whether sufficient degrees of freedom exist in these singlet flat directions to satisfy various phenomenological constraints imposed by the observed Standard Model data. For each flat direction, the effective superpotential is given to sixth order. The variations in the singlet and hidden sector low energy spectrums are analyzed. We then determine the mass matrices (to all finite orders) for the three generations of MSSM quarks and leptons. Possible Higgs mu-terms are investigated. We conclude by considering generalizations of our flat directions involving VEVs of non-Abelian fields.Comment: 41 pages. Standard Late

NAHE-based string models with SU(4) X SU(2) X U(1) SO(10) Subgroup

The orbifold GUT doublet-triplet splitting mechanism was discussed in 1994 in the framework of the NAHE-based free fermionic models in which the SO(10) GUT symmetry is broken to SO(6) X SO(4), SU(3) X SU(2) X U(1)^2, or SU(3) X U(1) X SU(2)^2. In this paper we study NAHE-based free fermionic models in which the SO(10) symmetry is broken at the string level to SU(4) X SU(2) X U(1). In addition to the doublet-triplet splitting this case also has the advantage of inducing the doublet-doublet splitting already at the string level. We demonstrate, however, that NAHE-based models with SU(4) X SU(2) X U(1) SO(10) subgroup are not viable. We show that, similarly to the LRS models, and in contrast to the FSU5, PS and SLM models, the SU421 case gives rise to models without an anomalous U(1) symmetry, and discuss the different cases in terms of their N=4 origins.Comment: 25 pages. Standard Latex. Revised version to appear in NP

Child protection, domestic violence and parental substance misuse : family experiences and effective practice : executive summary

This book draws on a wide range of evidence to explore the facts about the relationship between substance misuse and domestic violence and their effect on children, and examines the response of children's services when there are concerns about the safety and welfare of children. It reveals the vulnerability of these children and the extent to which domestic violence, parental alcohol or parental drug misuse impact on children's health and development, affect the adults' capacity to undertake key parenting tasks, and influence the response of wider family and the community. It includes parents' own voices and allows them to explain what help they feel would best support families in similar situations. The authors explore the extent to which current local authority plans, procedures, joint protocols and training support information sharing and collaborative working. Emphasising the importance of an holistic inter-agency approach to assessment, planning and service provision, the authors draw from the findings implications for policy and practice in both children and adult services

Stable Superstring Relics and Ultrahigh Energy Cosmic Rays

One of the most intriguing experimental results of recent years is the observation of Ultrahigh Energy Cosmic Rays (UHECRs) above the GZK cutoff. Plausible candidates for the UHECR primaries are the decay products of a meta--stable matter state with mass of order O(10^{12-15 GeV}), which simultaneously is a good cold dark matter candidate. We study possible meta-stable matter states that arise from Wilson line breaking of GUT symmetries in semi-realistic heterotic string models. In the models that we study the exotic matter states can be classified according to patterns of SO(10) symmetry breaking. We show that cryptons, which are states that carry fractional electric charge $\pm1/2$, and are confined by a hidden gauge group cannot produce viable dark matter. This is due to the fact that, in addition to the lightest neutral bound state, cryptons give rise to meta-stable charged bound states. However, these states may still account for the UHECR events. We argue that the uniton, which is an exotic Standard Model quark but carries ``fractional'' U(1)_{Z'} charge, as well as the singleton, which is a Standard Model singlet with ``fractional'' U(1)_{Z'} charge do provide viable dark matter candidates and can at the same time explain the observed UHECR events.Comment: 24 pages. 5 figure

Phenomenology of Non-Abelian Flat Directions in a Minimal Superstring Standard Model

Recently, we presented the first non-Abelian flat directions that produce from a heterotic string model solely the three-generation MSSM states as the massless spectrum in the observable sector of the low energy effective field theory. In this paper we continue to develop the systematic techniques for the analysis of nonrenormalizable superpotential terms and non-Abelian flat direction in realistic string models. Some of our non-Abelian directions were F-flat to all finite orders in the superpotential. We study for the same string model the varying phenomenologies resulting from a large set of such all-order flat directions. We focus on the quark, charged lepton, and Higgs doublet mass matrices resulting for our phenomenologically superior non-Abelian flat direction. We review and apply a string-related method for generating large mass hierarchies between MSSM generations, first discussed in string-derived flipped SU(5) models, when all generational mass terms are of renormalizable or very low non-renormalizable order