Robin G. Stuart

General renormalization of the gauge-invariant perturbation expansion near the Z0 resonanc

Abstract It was recently shown how to contrruct, to arbitrary accuracy, a perturbative expansion near the Z0 resonance that is exactly gauge invariant at each order. Here, a scheme-independent renormalization of the standard model is performed and the counter-term structure arising in the expansion for calculations to O(α) is given. The results can be easily specialized to the on-shell and MS renormalization schemes and are useful for studying the numerical differences between the two.

Electroweak corrections on the toponium resonance

Abstract The full one-loop electroweak radiative corrections to the longitudinal polarization asymmetry on the toponium resonance are evaluated. The techniques of the calculation are discussed in some detail. It is shown that to the order of interest the results are unaffected by QCD corrections. The dependence of the result on toponium and Higgs masses is studied. It is demonstrated that, after appropriate modifications, this calculation applies equally well to the forward-backward asymmetry in e + e − → ( t t ) → μ + μ − , and to asymmetries in the single quark decay.

Electroweak radiative corrections to b-quark production

Abstract The electroweak radiative corrections to the Z 0 b b and γ b b vertices are calculated in t Hooft-Feynman gauge in the standard model and are given in a compact form in terms of three universal functions. The results are obtained as the equal-mass limit of analogous flavour changing neutral current diagrams which avoids the need for fermion mass renormalization. The box diagram containing an internal top quark that occurs in the process e + e − → b b is also calculated.

Z0POLE. A program to calculate the electroweak and QCD radiative corrections to e+e- → ff near the Z0 resonance

Abstract We describe the program Z0POLE that evaluates the one-loop electroweak radiative corrections to the process e + e - → f f (f ≠ e - ) near the Z 0 resonance. QCD corrections are included up to O (α 3 s ) for light-quark doublets and up to O ( m 2 t α s ) for the t-b quark doublet. The program uses a calculational strategy that is based firmly on analytic S -matrix theory. It produces results that are demonstrably exactly gauge-invariant and that can be extended to include still higher-order corrections as they become necessary and available. Calculations are performed in either the popular “on-shell” or MS renormalization schemes. The results produced are accurate to 0.5% in the on-shell scheme and somewhat better for the MS scheme. A highly modular and transparent program structure has been employed. All formulas used in the code are given in this paper or appropriate references supplied.

The charge radius and anapole moment of a free fermion

We derive an expression for the charge radius and anapole moment of a free fermion induced at one loop in the standard Glashow-Salam-Weinberg model of electroweak interactions. The result, despite earlier claims to the contrary, is demonstrably gauge-invariant and observable in principle.

Semi-leptonic flavour-changing neutral-current decays of the fourth generation b′-quark

We study the decay modes b′ → bl+l−, b′ → bνν for minb′ ⪅MZ including virtual γ, Z0, and box diagram contributions, the latter complicating the computation considerably. Due to the effect of the Z0 propagator and the finite Z0 width, these decay rates are substantial. The box diagram is subleading but also not negligible. As a consequence, the lepton pair mass distribution is rather flat and high mass l+l− or νν pairs are much more abundant than suggested from phase space. It is found that b′ → bZ∗ (loosely denoting the sum of ifb′ → bl+l−, b′ → νν and b′ → bqq) is of similar order as the b′ → bg decay mode, and is likely to dominate in case mt′ is very heavy. With three light neutrinos, the decay b′ → bνν is similar order as b′ → b γ, however, the b′ → bl+l− mode are relatively suppressed. The flavour-changing neutral-current b′ decay scenario is thus shown to be quite rich. A comprehensive, but theoretical, discussion is given regarding b′ discovery potentials at present and future colliders.

The\(\overline {MS} \) and on-shell renormalization schemes in the analysis of neutrino scattering experiments

AbstractThe relationship between then

On estimating the top quark mass from global analyses ofe+e− collision data

overline {MS}