Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
1993-11-11
Phys.Rev.D49:4835-4841,1994
Physics
High Energy Physics
High Energy Physics - Phenomenology
LaTeX, 11 Pages+4 Figures(not included), the figures available upon request as an uuencoded file(0.4MB) or 4 PS files from par
Scientific paper
10.1103/PhysRevD.49.4835
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 $\Gamma_{l}, \Gamma_{b}, A^{l}_{FB}$, 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 ($m_{\chi^\pm_1}\lsim70\GeV$). 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 $\tan\beta\approx2$ 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 $\tan\beta\gsim4$, remains allowed and corresponds to light chargino masses ($m_{\chi^\pm_1}\lsim70\GeV$). 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.
Lopez Jorge L.
Nanopoulos Dimitri V.
Park Gye T.
Zichichi Antonino
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