Recent developments in precision electroweak physics

Abstract

Developments in precision electroweak physics in the two years since the symposium are briefly summarized.

Physics implications of precision electroweak experiments

“…The difference is mainly due to their use of an earlier estimate [20] ∆α (5) had (M Z ) = 0.02803 ± 0.00065. Gurtu reported that their M H increased to the consistent 88 +60 −37 GeV when they used a newer ∆α (5) had (M Z ) = 0.02755 ± 0.00046 [21] based on the new BES-II e + e − data. group and representations; does not explain charge quantization, the fermion families, or their masses and mixings; has several notorious fine tunings associated with the Higgs mass, the strong CP parameter, and the cosmological constant; and does not incorporate quantum gravity.…”

“…• The combination of WNC and WCC data uniquely determined the SU (2) representations of all of the known fermions, i.e., of the ν e and ν µ , as well as the L and R components of the e, µ, τ, d, s, b, u, and c [5]. In particular, the left-handed b was the lower component of an SU (2) doublet, implying unambiguously that the t quark had to exist.…”

“…Careful consideration of the competing definitions of the renormalized sin 2 θ W was needed. The principal theoretical uncertainty is the hadronic contribution ∆α (5) had (M Z ) to the running of α from its precisely known value at low energies [12] to the Z-pole [13], where it is needed to compare the Z mass with the asymmetries and other observables. The radiative corrections, renormalization schemes, and running of α are further discussed in Appendix B.…”

“…In fact, m t was successfully predicted from its indirect loop effects prior to the direct discovery at the Tevatron, while the indirect value of α s , mainly from the Z-lineshape, agreed with direct determinations. Similarly, ∆α (5) had (M Z ) and M H were constrained. The indirect (loop) effects implied M H < ∼ 194 GeV, while direct searches at LEP 2 yielded M H > 112 GeV, with a hint of a signal at 115 GeV.…”

“…However, ∆α (5) had (M Z ) can be determined from the indirect data alone, i.e., from the relation of M Z and M W to the other observables. The result, 0.02765 ± 0.00040, is in impressive agreement with the theoretical value.…”