The Character of Z-pole Data Constraints on Standard Model Parameters

Despite the impressive precision of the Z-pole measurements made at LEP and SLC, the allowed region for the principle Standard Model parameters responsible for radiative corrections (the mass of the Higgs, the mass of the top and alpha(Mz)) is still large enough to encompass significant non-linearities. The nature of the experimental constraints therefore depends in an interesting way on the "accidental" relationships among the various measurements. In particular, the fact that the Z-pole measurements favor values of the Higgs mass excluded by direct searches leads us to examine the effects of external Higgsstrahlung, a process ignored by the usual precision electroweak calculations.Comment: 9 pages, 6 figures, REVTeX format; added reference in section IV; added paragraph on widths and a few cosmetic changes to correspond to published versio

Radiative Corrections to Neutrino Deep Inelastic Scattering Revisited

Radiative corrections to neutrino deep inelastic scattering are revisited. One-loop electroweak corrections are re-calculated within the automatic SANC system. Terms with mass singularities are treated including higher order leading logarithmic corrections. Scheme dependence of corrections due to weak interactions is investigated. The results are implemented into the data analysis of the NOMAD experiment. The present theoretical accuracy in description of the process is discussed.Comment: 19 pages, two figures are added, discussion of theoretical uncertainties is extende

Universal Higher Order Singlet QED Corrections to Unpolarized Lepton Scattering

We calculate the universal flavor-singlet radiative QED corrections to unpolarized lepton scattering applicable to general differential scattering cross sections, involving charged fermions or photons in initial or final states. The radiators are derived to $O((\alpha \ln(Q^2/m_f^2))^5)$ in analytic form. Numerical illustrations are given.Comment: 31 pages, 3 figures, 1 style fil

Pinning down the kaon form factors in K^+ -> mu^+ nu_mu gamma decay

We find that the normal muon polarization in the decay K->mu nu_mu gamma is very sensitive to the values of the kaon vector F_V and axial-vector F_A form factors. It is shown that the ongoing KEK-E246 experiment can definitely determine the signs of the sum of the form factors if their difference is fixed from other considerations. This method can also verify the form factor values and signs obtained from the K^+ -> l^+ nu_l e^+ e^- decays. A new experiment with sensitivity to the normal and transverse muon polarizations of about 10^-4 will provide a unique possibility to determine the F_V and F_A values with a few percent accuracy.Comment: revtex, 5 pages, 2 figures. Minor corrections made for the journal version of the pape

MW and sin^2\theta_eff in Split SUSY: present and future expectations

We analyse the precision electroweak observables MW and sin^2\theta_eff and their correlations in the recently proposed Split SUSY model. We compare the results with the Standard Model and Minimal Supersymmetric Standard Model predictions, and with present and future experimental accuracies. Present experimental accuracies in (MW, sin^2\theta_eff) do not allow constraints to be placed on the Split SUSY parameter space. We find that the shifts in (MW, sin^2\theta_eff) induced by Split SUSY can be larger than the anticipated accuracy of the GigaZ option of the International Linear Collider, and that the most sensitive observable is sin^2\theta_eff. These large shifts are possible also for large chargino masses in scenarios with small tan(\beta) =~ 1.Comment: LaTeX, 13 pages, 4 figures. Comments adde

CP Violation in B and K Decays: 2003

These lectures give a brief description of CP violation in B and K meson decays with particular emphasize put on the determination of the CKM matrix. The following topics will be discussed: i) The CKM matrix, the unitarity triangle and general aspects of the theoretical framework, ii) Particle-antiparticle mixing and various types of CP violation, iii) Standard analysis of the unitarity triangle, iv) The ratio epsilon^prime/epsilon, v) The most important strategies for the determination of the angles $\alpha$, $\beta$ and $\gamma$ from B decays, vi) Rare decays $K^+\to\pi^+\nu\bar\nu$ and $K_L\to\pi^0\nu\bar\nu$ vii) Models with minimal flavour violation.Comment: Schladming lectures 2003, Main latex-file, 8 figures, 51 page

On Gauge Invariance of Breit-Wigner Propagators

We present an approach to bosonic ($Z^0, W^{\pm}$) as well as fermionic (top-quark) Breit-Wigner propagators which is consistent with gauge invariance arguments. In particular, for the $Z^0$-boson propagator we extend previous analyses and show that the part proportional to $k_{\mu} k_{\nu}/M^2$ must be modified near the resonance. We derive a mass shift which agrees with results obtained elsewhere by different methods. The modified form of a resonant heavy fermion propagator is also given.Comment: 16 p., TeX, (final version

Theoretical uncertainties for measurements of alpha_s from electroweak observables

One of the most precise measurements of the strong coupling constant alpha_s(MZ) is obtained in the context of global analyses of precision electroweak data. This article reviews the sensitivity of different electroweak observables to alpha_s and describes the perturbative uncertainties related to missing higher orders. The complete renormalisation scale dependence for the relevant observables is calculated at next-to-next-to-leading order and a new method is presented to determine the corresponding perturbative uncertainty for measurements of alpha_s based on these observables.Comment: v4: Revised version with new tables and figure

Calculation of the Two-Loop Heavy-Flavor Contribution to Bhabha Scattering

We describe in detail the calculation of the two-loop corrections to the QED Bhabha scattering cross section due to the vacuum polarization by heavy fermions. Our approach eliminates one mass scale from the most challenging part of the calculation and allows us to obtain the corrections in a closed analytical form. The result is valid for arbitrary values of the heavy fermion mass and the Mandelstam invariants, as long as s,t,u >> m_e^2.Comment: 43 pages, 8 figures; added reference

QED Radiative Corrections in Processes of Exclusive Pion Electroproduction

Formalism for radiative correction (RC) calculation in exclusive pion electroproduction on the proton is presented. A FORTRAN code EXCLURAD is developed for the RC procedure. The numerical analysis is done in the kinematics of current Jefferson Lab experiments.Comment: 13 pages, 9 figures; requires RevTeX