Precise Determination of |V{us}| from Lattice Calculations of Pseudoscalar Decay Constants

Combining the ratio of experimental kaon and pion decay widths, Gamma(K to mu antineutrino{mu} (gamma)) / Gamma(pi to mu \antineutrino (gamma)), with a recent lattice gauge theory calculation of f{K}/f{pi} provides a precise value for the CKM quark mixing matrix element |V{us}|=0.2236(30) or if 3 generation unitarity is assumed |V{us}|=0.2238(30). Comparison with other determinations of that fundamental parameter, implications, and an outlook for future improvements are given

Electroweak Radiative Corrections To Polarized M{\o}ller Scattering Asymmetries

One loop electroweak radiative corrections to left-right parity violating M{\o}ller scattering ($e^-e^-\to e^-e^-$) asymmetries are presented. They reduce the standard model (tree level) prediction by 40$\pm 3$ \% where the main shift and uncertainty stem from hadronic vacuum polarization loops. A similar reduction also occurs for the electron-electron atomic parity violating interaction. That effect can be attributed to an increase of $\sin^2\theta_W(q^2)$ by $3\%$ in running from $q^2=m_Z^2$ to 0. The sensitivity of the asymmetry to ``new physics'' is also discussed.Comment: 14 pages, Revtex, postscript file including figures is available at ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-14/ttp95-14.ps or via WWW at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints/ (129.13.102.139

Polarized Moller Scattering Asymmetries

The utility of polarized electron beams for precision electroweak studies is described. Parity violating Moller scattering asymmetries in e-e- --> e-e- are discussed. Effects of electroweak radiative corrections and the running sin^2(theta_W(Q^2)) are reviewed. The sensitivity of E158 (a fixed target e-e- experiment at SLAC) and future e-e- collider studies to ``new physics'' is briefly outlined.Comment: Updated Fig.

Radiative Tail in πe2\pi_{e2} Decay and Some Comments on μ−e\mu-e Universality

The result of lowest-order perturbation theory calculations of the photon and positron spectra in radiative pion(e2) decay are generalized to all orders of perturbation theory using the structure-function method. An additional source of radiative corrections to the ratio of the positron and muon channels of pion decay, due to emission of virtual and real photons and pairs, is considered. It depends on details of the detection of the final particles and is large enough to be taken into account in theoretical estimates with a level of accuracy of 0.1%.Comment: 5 pages, LaTeX, some misprints are corrected, submitted to Pisma Zh. Eksp. Teor. Fi

K_L \ra \mu^\pm e^\mp \nu \overline{\nu} as background to K_L \ra \mu^\pm e^\mp

We consider the process K_L \ra \mu^\pm e^\mp \nu \overline{\nu} at next to leading order in chiral perturbation theory. This process occurs in the standard model at second order in the weak interaction and constitutes a potential background in searches for new physics through the modes K_L \ra \mu^\pm e^\mp. We find that the same cut, $M_{\mu e}>489$~MeV, used to remove the sequential decays K_{l3}\ra \pi_{l2} pushes the B(K_L \ra \mu^\pm e^\mp \nu \overline{\nu}) to the $10^{-23}$ level, effectively removing it as a background.Comment: 8 pages, LaTeX, 1 figure appended as postscript file after \end{document}. Fermilab-Pub-93/024-

Fermi Constants and ``New Physics''

Various precision determinations of the Fermi constant are compared. Included are muon and (leptonic) tau decays as well as indirect prescriptions employing \alpha, m_Z, m_W, \ssthwmzms, \Gamma(Z\to\ell^+\ell^-), and $\Gamma(Z \to \nu\bar \nu)$ as input. Their good agreement tests the standard model at the $\pm 0.1$ level and provides stringent constraints on new physics. That utility is illustrated for: heavy neutrino mixing, 2 Higgs doublet models, S, T, and U parameters and excited $W^{\ast^\pm}$ bosons (Kaluza-Klein excitations). For the last of those examples, m_{W^\ast}\gsims 2.9 TeV is found.Comment: 14 page

Electroweak higher-order effects and theoretical uncertainties in deep-inelastic neutrino scattering

A previous calculation of electroweak O(alpha) corrections to deep-inelastic neutrino scattering, as e.g. measured by NuTeV and NOMAD, is supplemented by higher-order effects. In detail, we take into account universal two-loop effects from \Delta\alpha and \Delta\rho as well as higher-order final-state photon radiation off muons in the structure function approach. Moreover, we make use of the recently released O(alpha)-improved parton distributions MRST2004QED and identify the relevant QED factorization scheme, which is DIS like. As a technical byproduct, we describe slicing and subtraction techniques for an efficient calculation of a new type of real corrections that are induced by the generated photon distribution. A numerical discussion of the higher-order effects suggests that the remaining theoretical uncertainty from unknown electroweak corrections is dominated by non-universal two-loop effects and is of the order 0.0003 when translated into a shift in sin^2\theta_W=1-MW^2/MZ^2. The O(alpha) corrections implicitly included in the parton distributions lead to a shift of about 0.0004.Comment: 25 pages, latex, 8 postscript figure

Dynamical CP Violation in Composite Higgs Models

The dynamical origin of the CP violation in electroweak theory is investigated in composite Higgs models. The mechanism of the spontaneous CP violation proposed in other context by Dashen is adopted to construct simple models of the dynamical CP violation. Within the models the size of the neutron electric dipole moment is estimated and the constraint on the $\varepsilon$-parameter in K-meson decays is discussed.Comment: 20 pages, 2 figures not included, uses LaTeX, HUPD-922

SM Kaluza-Klein Excitations and Electroweak Precision Tests

We consider a minimal extension to higher dimensions of the Standard Model, having one compactified dimension, and we study its experimental tests in terms of electroweak data. We discuss tests from high-energy data at the $Z$-pole, and low-energy tests, notably from atomic parity violation data. This measurement combined with neutrino scattering data strongly restricts the allowed region of the model parameters. Furthermore this region is incompatible at 95% CL with the restrictions from high-energy experiments. Of course a global fit to all data is possible but the $\chi^2_{\rm min}$ for degree of freedom is unpleasantly large.Comment: LaTex, 14 pages, 2 figures. More refs. and one comment about the validity of our results for any number of extra dimensions adde