Precision tests of the electroweak interaction

Abstract

Recent measurements of various charged current and neutral current processes are presented and compared with the prediction of the Standard Model of the Electroweak Interaction. No discrepancy was found in the experiments'precision which is often higher than 0.

Future High Precision Experiments and New Physics Beyond Standard Model

“…Their SM predictions and experimental errors are listed in Table 1.1. There axe already some preliminary results of them from LEP [2]. We note that the errors on the forward-backward asymmetry of the u is 0.0027, which is lower than the anticipated error 0.0035.…”

“…the QED coupling constant, the Fermi weak interaction coupling constant, and the weak mixing angle. _ and Gr have already been determined precisely by other experiments, sin"_ Ow is the single unspecified parameter in the GWS theory, representing the mixing between the SU (2) and U(1) sectors. At tree level, sin20w is given by g,_/(g,2 + gs), where 9 and g' axe respectively the SU (2) and U(1) gauge coupling constants.…”

“…These heavy physics will affect the neutral current and W, g observables by shifting the self-energy diagrams. These shifts can be parametrized in terms of three parameters, hv = T, haw and haz, where hv (hA) refers to the breaking of the vector (axial) part of SU (2). In most cases, the axial parameters are approximately equal, haw "-"haz = S. hv is sensitive to nondegenerate SU(2) multiplets which break the vector SU(2) symmetries, including the top quark mass, non-degenerate fourth family fermions, non-degenerate Higgs multiplets, and b-t splitting in supersymmetry.…”

“…A few years ago, a theoretical framework was developed for the analysis of the high precision electroweak experiments that were likely to be done in the next ten years [1]. Since then, significant experimental progresses have been made, especially at the _+e-collider LEP at CERN [2]. The mass of the 2 boson Mz has been shifted from 91.177 to 91.187 GeV, the error on Mz, AMz, has been reduced from 0.031 to 0.007 GeV, which is much better than the error anticipated.…”

“…In this decade, there have been and will be performed a series of high precision experiments relating to the properties of the Z-and w-bosons and to weak neutral current observables. As mentioned at the beginning, the z-boson mass has already been measured very precisely [2]. The decaying widths of Z, the forwardbackward and possibly polarization asymmetries in e+e-collisions, and the W boson mass have been or will be measured with high but somewhat less precision (see [6]- [9] and references in [1]).…”