New Precision Electroweak Tests of SU(5) x U(1) Supergravity

Abstract

We explore the one-loop electroweak radiative corrections in $SU(5)\times U(1)$ supergravity via explicit calculation of vacuum-polarization and vertex-correction contributions to the ${\epsilon }_1$ and ${\epsilon }_b$ parameters. Experimentally, these parameters are obtained from a global fit to the set of observables ${\Gamma }_l,{\Gamma }_b,A_{FB}^l$, and $M_W/M_Z$. We include $q^2$-dependent effects, which induce a large systematic negative shift on ${\epsilon }_1$ for light chargino masses ($m_{χ^\pm_1}\lsim70\GeV$). The (non-oblique) supersymmetric vertex corrections to $\Zbb$, which define the ${\epsilon }_b$ parameter, show a significant positive shift for light chargino masses, which for $\tan \beta \approx 2$ can be nearly compensated by a negative shift from the charged Higgs contribution. We conclude that at the 90\%CL, for $m_t\lsim160\GeV$ the present experimental values of ${\epsilon }_1$ and ${\epsilon }_b$ do not constrain in any way $SU(5)\times U(1)$ supergravity in both no-scale and dilaton scenarios. On the other hand, for $m_t\gsim160\GeV$ the constraints on the parameter space become increasingly stricter. We demonstrate this trend with a study of the $m_t=170\GeV$ case, where only a small region of parameter space, with $\tanβ\gsim4$, remains allowed and corresponds to light chargino masses ($m_{χ^\pm_1}\lsim70\GeV$). Thus $SU(5)\times U(1)$ supergravity combined with high-precision LEP data would suggest the presence of light charginos if the top quark is not detected at the Tevatron.

LaTeX, 11 Pages+4 Figures(not included), the figures available upon request as an uuencoded file(0.4MB) or 4 PS files from [email protected], CERN-TH.7078/93, CTP-TAMU-68/93, ACT-24/93

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Cited by in corpus (7)

• Higgs and Supersymmetric Particle Signals at the Infrared Fixed Point of the Top Quark Mass
• $R_b$ in supersymmetric models
• Experimental aspects of SU(5)xU(1) supergravity
• ${\epsilon }_b$ Constraints on the Minimal $SU(5)$ and $SU(5)\times U(1)$ Supergravity Models
• Precision Electroweak Tests on the $Sp(6{)}_L\times U(1{)}_Y$ Model
• Probing Supergravity Models with Indirect Experimental Signatures
• New Precision Electroweak Tests in Supergravity Models