Two-loop heavy top effects on the MZ-MW interdependence

The O(alpha^2 mt^2/mw^2) correction to the relation between G_\mu and the vector boson masses is computed in the MSbar scheme, and the results are used to investigate the magnitude of the effect on the theoretical prediction of mw and sin^2\theta_\msbar(mz) from alpha, G_\mu, and mz.Comment: 11 pages, LaTeX, includes 1 LaTeX figure, uses equations.sty and cite.sty, one minor comment and interpolation function for variable mtop added, no change in the result

Topics in Electroweak Physics

We briefly discuss five topics in Precision Electroweak Physics: i) the recently proposed Effective Scheme of Renormalization, ii) evidence for electroweak bosonic corrections derived from the radiative correction Delta_r_eff, iii) an approach to estimate the scale of new physics in a hypothetical Higgs-less scenario, iv) simple and accurate formulae for s^2_eff, M_W, Gamma_l, and their physical applications, v) a recent proposal concerning the field renormalization constant for unstable particles.Comment: 5 pages, talk presented at the International Symposium Radcor 2002, September 8-13, Kloster Banz, German

The role of the top quark in the stability of the SM Higgs potential

I discuss the stability of the SM scalar potential in view of the discovery of a Higgs boson with mass around 125 GeV. The role played by the top quark mass in the choice between the full stability and the metastability conditions is analyzed in detail. The present experimental value of the top mass do not support the possibility that the SM potential is stable up to the Planck scale but favor an electroweak vacuum sufficiently long-lived to be metastable.Comment: 7 pages, 6 figures. To appear on the Proceedings of LC13 Workshop: exploring QCD from the infrared regime to heavy flavour scales at B-factories, the LHC and a Linear Collider, 16-20 September 2013, ECT*, Villa Tambosi, Villazzano (TN), Ital

Accurate prediction of electroweak observables and impact on the Higgs mass bound

I discuss the importance of the O(g^4 m_t^2/\mw^2) corrections to the effective electroweak angle and Mw in the indirect determination of the Higgs mass. I emphasize the r\^ole of a very precise Mw measurement on the Mh estimate.Comment: 9 pages, LaTex, uses appb.sty. Talk presented at the Zeuthen Workshop on Elementary Particle Theory "Loops and Legs in Gauge Theories" Rheinsberg, Germany, April 19-24, 199

Consistency Condition for the Pinch Technique Self-Energies at Two Loops

A simple and testable necessary condition for the gauge independence of the Pinch Technique self-energies at two loops is discussed. It is then shown that, in the case of the $Z$ and $W$ self-energies, the condition is indeed satisfied by the Papavassiliou-Pilaftsis formulation.Comment: 7 pages, Latex, 1 PostScript figur

Electroweak effects in the B0−Bˉ0B^0-{\bar B}^0 mixing

We compute analytically the complete electroweak two-loop corrections to the $B^0-{\bar B}^0$ mixing. These corrections fix the normalization of the electroweak coupling employed in the extraction of $|V_{td}|$ and reduce the theoretical uncertainty due to higher order electroweak effects from several percent to a few parts in a thousand. If the LO result is expressed in terms of $G_\mu$ or of the $\bar{MS}$ coupling $\hat{g}(M_Z)$, the two-loop corrections are $O(1$, the exact value depending on the mass of the Higgs boson. We discuss in detail the renormalization procedure and the scheme and scale dependence, and provide practical formulas for the numerical implementation of our results. We also consider the heavy top mass expansion and show that in the case at hand it converges very slowly.Comment: LaTeX, 29 pages, 6 postscript figures include

The electroweak form factor \hat{\kappa}(q^2) and the running of \sin^2 \hat{\theta}_W

Gauge independent form factors \rho^(e; e) and \hat{\kappa}^(e; e)(q^2) for Moller scattering at s << m_W^2 are derived. It is pointed out that \hat{\kappa}^(e; e) is very different from its counterparts in other processes. The relation between the effective parameter \hat{\kappa}^(e; e)(q^2,\mu) \sin^2 \hat{\theta}_W(\mu) and \sin^2 \theta_eff is derived in a scale-independent manner. A gauge and process-independent running parameter \sin^2 \hat{\theta}_W (q^2), based on the pinch-technique self-energy a_{\gamma Z} (q^2), is discussed for all q^2 values. At q^2=0 it absorbs very accurately the Czarnecki-Marciano calculation of the Moller scattering asymmetry at low s values, and at q^2 = m^2_Z it is rather close to \sin^2 \theta_eff. The q^2 dependence of \sin^2 \hat{\theta}_W (q^2) is displayed in the space and time-like domains.Comment: A new paragraph has been inserted at the beginning of the discussion in Section