The top-quark mass in SU(5)xU(1) supergravity

Abstract

We show that the currently experimentally preferred values of the top-quark mass (\ie, $130\lsim m_t\lsim180\GeV$) are naturally understood in the context of string models, where the top-quark Yukawa coupling at the string scale is generically given by ${\lambda }_t=\mathcal{O}(g)$, with $g$ the unified gauge coupling. A detailed study of the Yukawa sector of $SU(5)\times U(1)$ supergravity shows that the ratio of the bottom-quark to tau-lepton Yukawa couplings at the string scale is required to be in the range $0.7\lsimλ_b/λ_τ\lsim1$, depending on the values of $m_t$ and $m_b$. This result is consistent with $SU(5)\times U(1)$ symmetry, which does {\em not} require the equality of these Yukawa couplings in the unbroken symmetry phase of the theory. As a means of possibly predicting the value of $m_t$, we propose a procedure whereby the size of the allowed parameter space is determined as a function of $m_t$, since all sparticle and Higgs-boson masses and couplings depend non-trivially on $m_t$. At present, no significant preference for particular values of $m_t$ in $SU(5)\times U(1)$ supergravity is observed, except that high-precision LEP data requires $m_t\lsim180\GeV$.

latex, 10 pages, 4 figures (included), CERN-TH.7138/94, CTP-TAMU-05/94

References in corpus (22)

• Model-Independent Analysis of Soft Terms in Effective Supergravity and in String Theory
• Duality Anomaly Cancellation, Minimal String Unification and the Effective Low-Energy Lagrangian of 4-D Strings
• Supersymmetric Grand Unified Theories: Two Loop Evolution of Gauge and Yukawa Couplings
• One-Loop Analysis of the Electroweak Breaking in Supersymmetric Models and the Fine-Tuning Problems
• "Large $(g-2{)}_{\mu }$ in SU(5)xU(1) supergravity models"
• Construction of Realistic Standard--like Models in the Free Fermionic Superstring Formulation
• The Search for a realistic flipped SU(5) string model
• Phenomenological Implications of the $m_t$ RGE Fixed Point for SUSY Higgs Boson Searches
• Phenomenological Implications of the m_t RGE Fixed Point for SUSY Higgs Boson Searches
• Sparticle Spectrum Constraints
• Bottom-Up Approach to Uniefied Supergravity Models
• Infrared Fixed Point Solution for the Top Quark Mass and Unification of Couplings in the MSSM
• Aspects of Radiative Electroweak Symmetry Breaking in Supergravity Models
• Implications for Minimal Supersymmetry from Grand Unification and the Neutralino Relic Abundance
• Probing supergravity models with the $b\to s\gamma$ microscope
• Supersymmetry Tests at Fermilab: A Proposal
• The strongest experimental constraints on SU(5)xU(1) supergravity models
• The Simplest, String-Derivable, Supergravity Model and its Experimental Predictions
• Towards a unified string supergravity model
• Light Gluinos and Unification of Couplings
• Precision Electroweak Tests of the Minimal and Flipped SU(5) Supergravity Models
• Radiative Symmetry Breaking and the Top Quark Mass in Local Supersymmetry

Cited by in corpus (3)

• A string no-scale supergravity model and its experimental consequences
• Large Top and Bottom Yukawa Couplings in Minimal Supersymmetry
• String and string-inspired phenomenology