The problems of unification-mismatch and low ${\alpha }_3$: A solution with light vector-like matter

Abstract

The commonly accepted notion of a weak unified coupling ${\alpha }_X\approx 0.04$, based on the assumption of the MSSM--spectrum, is questioned. It is suggested that the four--dimensional unified string coupling should very likely have an intermediate value $(\sim 0.2-0.3$, say) so that it may be large enough to stabilize the dilaton but not so large as to disturb the coupling--unification relations. Bearing this in mind, as well as the smallness of the MSSM unification scale $M_X$ compared to the string scale, the consequences of a previously suggested extension of the MSSM spectrum are explored. The extension contains two vector--like families of quarks and leptons with relatively light masses of order 1 TeV, having the quantum numbers of $16+\overline{16}$ of $SO(10)$. It is observed that such an extension provides certain unique advantages. These include: (a) removing the stated mismatch between MSSM and string unifications with regard to ${\alpha }_X$ and to some extent $M_X$ as well, (b) achieving coupling unification with a relatively low value of ${\alpha }_3(m_Z)$, in accord with its world average value, and (c) following earlier works, providing a simple explanation of the observed inter--family mass--hierarchy. The extension provides scope for exciting new discoveries, beyond those of SUSY and Higgs particles, at future colliders, including the LHC and the NLC.

21 pages in LaTeX, includes 3 figures

References in corpus (12)

• String Theory Dynamics In Various Dimensions
• Heterotic and Type I String Dynamics from Eleven Dimensions
• Coping With Strongly Coupled String Theory
• Precision Corrections to Supersymmetric Unification
• The strong coupling, unification, and recent data
• Gauge Coupling Unification in Realistic Free-Fermionic String Models
• Natural gauge-coupling unification at the string scale
• ${\sin }^2{\theta }_W(M_Z)$ ~in the MSSM and Unification of Couplings
• Coupling Constant Unification in Extended SUSY Models
• Effective couplings and Perturbative Unification
• Light thresholds in Grand Unified Theories
• "A Hint From the Inter-Family Mass Hierarchy: Two Vector-Like Families in the TeV range"

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