The Direct Limit on the Higgs Mass and the SM Fit

Abstract

Because of two $3\sigma$ anomalies, the Standard Model (SM) fit of the precision electroweak data has a poor confidence level, $CL= 0.02$. Since both anomalies involve challenging systematic issues, it might appear that the SM could still be valid if the anomalies resulted from underestimated systematic error. Indeed the $CL$ of the global fit could then increase to 0.71, but that fit predicts a small Higgs boson mass, $m_H=45$ GeV, that is inconsistent at 95% CL with the lower limit, $m_H>114$ GeV, established by direct searches. The data then favor new physics if the anomalous measurements are both excluded or both retained, and the Higgs boson mass cannot be predicted until the new physics is understood. The validity of the SM could however be maintained by a propitious combination of statistical fluctuation and systematic error. The current data do not allow a definitive conclusion.