https://biblio.ugent.be/publication/685594/file/1130605.pdf

Review of Particle Physics

http://cds.cern.ch/record/147992/files/198312192.pdf

Chiral perturbation theory to one loop

This article reports world averages of measurements of b-hadron, c-hadron, and tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available through the end of 2011. In some cases results available in the early part of 2012 are included. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays and CKM matrix elements.

/pdf/averages-of-b-hadron-c-hadron-and-tau-lepton-properties-as-29qrkk2j2g.pdf

Averages of b-hadron, c-hadron, and tau-lepton properties as of early 2012

I will first review the experimental limits placed on the oblique correction parameters S and T. Then, I will discuss how the value of S can be estimated for running and walking technicolor theories.

/pdf/estimation-of-oblique-electroweak-corrections-1puptfhw6n.pdf

Estimation of oblique electroweak corrections

Unified Interactions of Leptons and Hadrons

An analysis of electroweak radiative corrections to \ensuremath{\tau} decays is presented. Precise predictions for leptonic and some hadronic decay rates are given. The total hadronic decay width is shown to be relatively enhanced by 2.36% due mainly to short-distance loop effects. Implications for the extraction of ${\ensuremath{\Lambda}}_{\mathrm{MS}\mathrm{\ifmmode\bar\else\textasciimacron\fi{}}}$ from the \ensuremath{\tau} lifetime or leptonic branching ratios are discussed. (MS\ifmmode\bar\else\textasciimacron\fi{} denotes the modified minimal-subtraction scheme.)

Electroweak radiative corrections to tau decay.

The results of a comprehensive analysis of existing data on the weak neutral current and the W and Z masses are presented. The principal results are the following. (a) There is no evidence for any deviation from the standard model. (b) A global fit to all data yields ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$\ensuremath{\equiv}1-${\mathrm{M}}_{\mathrm{W}}$${\mathrm{}}^{2}$/${\mathrm{M}}_{\mathrm{Z}}$${\mathrm{}}^{2}$=0.230\ifmmode\pm\else\textpm\fi{}0.0048, where this error and all others given here include full statistical, systematic, and theoretical uncertainties (computed assuming three fermion families, ${m}_{t}$\ensuremath{\le}100 GeV, and ${M}_{H}$\ensuremath{\le}1 TeV). (c) Allowing \ensuremath{\rho}\ensuremath{\equiv}${M}_{W}$${\mathrm{}}^{2}$/(${M}_{Z}$${}^{2}$${\mathrm{cos}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$) as well as ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$ to vary one obtains ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$=0.229\ifmmode\pm\else\textpm\fi{}0.0064 and \ensuremath{\rho}=0.998\ifmmode\pm\else\textpm\fi{}0.0086. This implies 90%-confidence-level (C.L.) upper limits of 0.047 and 0.081 for the vacuum expectation values (relative to those of Higgs doublets) for Higgs triplets with weak hypercharge of 0 and \ifmmode\pm\else\textpm\fi{}1, respectively. (d) The parameter ${\ensuremath{\delta}}_{W}$\ensuremath{\equiv}\ensuremath{\Delta}r-\ensuremath{\Delta}${s}^{2}$(1-\ensuremath{\Delta}r)/${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}^{0}$, which is a measure of the radiative corrections relating deep-inelastic neutrino scattering, the W and Z masses, and muon decay, is determined to be 0.112\ifmmode\pm\else\textpm\fi{}0.037. This is consistent with the value ${\ensuremath{\delta}}_{W}$=0.106 expected for ${m}_{t}$=45 GeV and ${M}_{H}$=100 GeV and establishes the existence of radiative corrections at the 3\ensuremath{\sigma} level. (e) The radiative corrections are sensitive to isospin breaking associated with a large ${m}_{t}$.Assuming no deviation from the standard model, consistency of the various reactions requires ${m}_{t}$180 GeV at 90% C.L. for ${M}_{H}$\ensuremath{\le}100 GeV, with a slightly weaker limit for larger ${M}_{H}$. Similar results hold for the mass splittings between fourth-generation quarks or leptons. (f) Most of the parameters in model-independent fits to \ensuremath{\nu}q, \ensuremath{\nu}e, eq, and ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ processes are now determined uniquely and precisely. (g) Limits are given on the masses and mixing angles of additional Z bosons expected in popular models. For theoretically expected coupling constants one finds that the neutral-current constraints are usually more stringent than the direct-production limits from the CERN Sp\ifmmode\bar\else\textasciimacron\fi{}pS collider, but nevertheless masses as low as 120--300 GeV are typically allowed. (h) The implications of these results for grand unification are discussed. ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$ is \ensuremath{\ge}2.5 standard deviations above the prediction of minimal SU(5) and similar models for all ${m}_{t}$. It is closer to the prediction of simple supersymmetric grand unified theories but is still somewhat low. (i) The dominant theoretical uncertainty (the charm-quark threshold in deep-inelastic charged-current scattering) is considered in some detail.

/pdf/comprehensive-analysis-of-data-pertaining-to-the-weak-48cxes1mg4.pdf

Comprehensive analysis of data pertaining to the weak neutral current and the intermediate-vector-boson masses.

A class of three-space-dimensional soliton solutions is given; these solitons are made of scalar fields and are of a nontopological nature. The necessary conditions for having such soliton solutions are (I) the conservation of an additive quantum number, say Q, and (II) the presence of a neutral (Q = 0) scalar field. It is shown that there exist two critical values of the additive quantum number, Q/sub C/ and Q/sub S/, with Q/sub C/ smaller than Q/sub S/. Soliton solutions exist for Q > Q/sub C/. When Q > Q/sub S/, the lowest soliton mass is Qm; never and Q/sub S/, the soliton mass is > Qm; nevertheless, the lowest-energy soliton solution can be shown to be always classically stable, though quantum-mechanically metastable. The canonical quantization procedures are carried out. General theorems on stability are established, and specific numerical results of the soliton solutions are given. (AIP)

Class of scalar-field soliton solutions in three space dimensions

A current algebra formulation of the radiative corrections in gauge theories, with special applications to the analysis of the universality of the weak interactions, is developed in the framework of quantum chromodynamics. For definiteness, we work in the SU(2)\ifmmode\times\else\texttimes\fi{}U(1) model with four quark flavors, but the methods are quite general and can be applied to other theories. The explicit cancellation of ultraviolet divergences for arbitrary semileptonic processes is achieved relying solely on the Ward identities and general considerations, both in the $W$ and Higgs sectors. The finite parts of order ${G}_{F}\ensuremath{\alpha}$ are then evaluated in the case of the superallowed Fermi transitions, including small effects proportional to ${g}_{s}^{\ensuremath{-}2}({\ensuremath{\kappa}}^{2})$, which are induced by the strong interactions in the asymptotic domain. We consider here both the simplest version of the Weinberg-Salam model in which the Higgs scalars transform as a single isospinor, as well as the case of general symmetry breaking. Except for the small effects proportional to ${g}_{s}^{\ensuremath{-}2}({\ensuremath{\kappa}}^{2})$, the results are identical to the answers previously found on the basis of heuristic arguments. The phenomenological verification of Cabibbo universality on the basis of these corrections and the superallowed Fermi transitions has been discussed before and found to be in very good agreement with present experimental evidence. The analogous calculation for the transition rate of pion $\ensuremath{\beta}$ decay is given. Theoretical alternatives to quantum chromodynamics as a framework for the evaluation of the radiative corrections are briefly discussed. The appendixes contain a generalization of an important result in the theory of radiative corrections due to L. S. Brown, G. Preparata, and W. I. Weisberger, an analysis of the hadronic contributions to the $W$ and $\ensuremath{\varphi}$ propagators, mathematical methods for evaluating the ${g}_{s}^{\ensuremath{-}2}({\ensuremath{\kappa}}^{2})$ corrections, and discussions of quark mass renormalization and the absence of operator "seagulls" in the hadronic correlation functions. Some of the methods discussed in this paper can also be applied to the study of radiative corrections of order ${G}_{F}\ensuremath{\alpha}$ to other processes affected by the strong interactions.

Current algebra formulation of radiative corrections in gauge theories and the universality of the weak interactions

A new method for computing hadronic effects on electroweak radiative corrections to low-energy weak interaction semileptonic processes is described. It employs high order perturbative QCD results originally derived for the Bjorken sum rule along with a large $N$ QCD-motivated interpolating function that matches long- and short-distance loop contributions. Applying this approach to the extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element ${V}_{ud}$ from superallowed nuclear beta decays reduces the theoretical loop uncertainty by about a factor of 2 and gives ${V}_{ud}=0.973\text{ }77(11)(15)(19)$. Implications for CKM unitarity are briefly discussed.

Alberto Sirlin

Papers

Electroweak radiative corrections to tau decay.

Comprehensive analysis of data pertaining to the weak neutral current and the intermediate-vector-boson masses.

Class of scalar-field soliton solutions in three space dimensions

Current algebra formulation of radiative corrections in gauge theories and the universality of the weak interactions

Improved Calculation of Electroweak Radiative Corrections and the Value of V u d