arXiv subjects

G. Degrassi

Publications and source records attributed to G. Degrassi.

42 records · Page 3Linked to original sources

arXiv1996

Fermion Virtual Effects in $e^+ e^- -> W^+ W^-$ Cross Section

We analyse the contribution of new heavy virtual fermions to the $e^+e^- \rightarrow W^+W^-$ cross section. We find that there exists a relevant interplay between trilinear and bilinear oblique corrections. The result strongly depends on the chiral or vector--like nature of the new fermions. As for the chiral case we consider sequential fermions: one obtains substantial deviation from the Standard model prediction, making the effect possibly detectable at $\sqrt{s}=500$ or $1000$ GeV linear colliders. As an example for the vector--like case we take a SUSY extension with heavy charginos and neutralinos: due to cancellation, the final effect turns out to be negligible.

hep-ph↗

arXiv1996

Two-loop heavy top effects on the MZ-MW interdependence

The O(alpha^2 mt^2/mw^2) correction to the relation between G_μand the vector boson masses is computed in the MSbar scheme, and the results are used to investigate the magnitude of the effect on the theoretical prediction of mw and sin^2θ_\msbar(mz) from alpha, G_μ, and mz.

hep-ph↗

arXiv1996

Searches For New Physics

Review of prospects for discovery of new physics signals at LEP2. The areas covered include SUSY, exotic fermions, BESS models, leptoquarks, virtual effects and CP violating observables.

hep-ph↗

arXiv1995

Two-loop Corrections for Electroweak Processes

Theoretical uncertainties affecting electroweak observables are reviewed and the relevance of two-loop electroweak radiative corrections for the precision tests of the Standard Model is discussed.

hep-ph↗

arXiv1994

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

The assumption that two-loop top corrections are well approximated by the $O(G_mu^2 mt^4)$ contribution is investigated. It is shown that in the case of the ratio neutral-to-charged current amplitudes at zero momentum transfer the $O(G_mu^2 mt^2 M_Z^2)$ 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.

hep-ph↗

arXiv1994

Two-loop next-to-leading $\mt$ corrections to the $ρ$ parameter

The $O(G^2_μm_t^4)$ correction to the $ρ$ parameter is computed within the Standard Model using the current algebra formulation of radiative corrections. This approach is proved to be equivalent to the effective Lagrangian method proposed by Barbieri {\em et al.} Using the same framework, the $O(G^2_μm_t^2 m_z^2)$ correction to the ratio of neutral-to-charged current amplitudes is analysed in an $SU(2)$ model. The $O(G^2_μm_t^2 m_z^2)$ contribution is shown to be numerically comparable to the leading $O(G^2_μm_t^4)$ term for realistic values of the top mass. The resummation of higher-order effects is discussed.

hep-ph↗