A General Treatment of Oblique Parameters

A reexamination is made of one-loop oblique electroweak corrections. General definitions are given of the oblique parameters without reference to any q-expansion scheme. The old oblique parameters S,T and U are defined as differences of gauge boson vacuum polarization Π-functions and suffice to describe certain observable ratios on the Z-peak and the ρ parameter at q = 0. Regarding the new oblique parameters V,W and X, the first two are defined in terms of differences of Π-functions as well as the wavefunction renormalization of the corresponding weak boson, and the third in terms of the difference of differences of two Π-functions for γ − Z mixing. Explicit expressions for measurable quantities involving all six oblique parameters are given and experimental bounds are obtained on the latter, some for the first time. A review of these constraints suggests that the linear approximation of Peskin and Takeuchi is robust. Electronic address: [email protected] Electronic address: [email protected]