Two-loop electroweak top corrections: are they under control?

Abstract

The assumption that two-loop top corrections are well approximated by the $O(G_m{u}^{2}m{t}^4)$ contribution is investigated. It is shown that in the case of the ratio neutral-to-charged current amplitudes at zero momentum transfer the $O(G_m{u}^{2}m{t}^2{M}_Z^2)$ terms are numerically comparable to the $m_t^4$ contribution for realistic values of the top mass. An estimate of the theoretical error due to unknown two-loop top effect is presented for a few observables of LEP interest.

13 pages, LaTeX using equations, doublespace, cite macros. Hard copies of the paper including one figure are available from [email protected]

References in corpus (3)

• Two-loop two-point functions with masses: asymptotic expansions and Taylor series, in any dimension
• Radiative Correction Effects of a Very Heavy Top
• $Ø(\GF^2\Mt^4)$ Electroweak Radiative Corrections to the $\PZ\Pb\Pbbar$ Vertex

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• Two-loop renormalization of the electric charge in the Standard Model
• Exact O(g^2 alpha_s) top decay width from general massive two-loop integrals
• Exact non-factorizable O(alpha_s g^2) two-loop contribution to Z -> b bbar
• Resummed corrections to the ρparameter due to a finite width of the top quark
• Heavy top renormalon contribution to fermion propagators