The Experimental Status of the Standard Electroweak Model at the End of the LEP-SLC Era

TL;DR

This paper evaluates how well the Standard Model matches experimental data from LEP and SLC, confirming quantum corrections but noting some deviations, and proposes a method to assess confidence levels combining direct and indirect Higgs searches.

Contribution

It introduces a method to calculate confidence levels for data agreement with the Standard Model, integrating direct and indirect Higgs search results, and provides updated assessments of the model's validity.

Findings

Good agreement with SM for Higgs mass around 120 GeV.

Quantum corrections predicted by SM are observed with high significance.

Some deviations from SM are identified in specific couplings.

Abstract

A method is proposed to calculate the confidence level for agreement of data with the Standard Model (SM) by combining information from direct and indirect Higgs Boson searches. Good agreement with the SM is found for $m_H \simeq 120$ GeV using the observables most sensitive to $m_H$: $A_l$ and $m_W$. In particular, quantum corrections, as predicted by the SM, are observed with a statistical significance of forty-four standard deviations. However, apparent deviations from the SM of 3.7$\sigma$ and 2.8$\sigma$ are found for the Z$\nu \bar{\nu}$ and right-handed Zb$\bar{{\rm b}}$ couplings respectively. The maximum confidence level for agreement with the SM of the entire data set considered is $\simeq 0.006$ for $m_H \simeq 180$ GeV. The reason why confidence levels about an order of magnitude higher than this have been claimed for global fits to similar data sets is explained.