The muon g-2 discrepancy: new physics or a relatively light Higgs?

TL;DR

This paper reviews the muon g-2 anomaly, examines potential Standard Model errors, and explores implications for the Higgs boson mass, suggesting a narrow window if the discrepancy is due to underestimated hadronic effects.

Contribution

It analyzes the likelihood of various Standard Model errors explaining the muon g-2 discrepancy and discusses the resulting constraints on the Higgs boson mass.

Findings

Hypothetical errors in the Standard Model are unlikely to explain the discrepancy.

An increase in low-energy hadroproduction cross section is also unlikely based on current data.

If the discrepancy is due to underestimated hadronic effects, the Higgs mass upper bound is about 135 GeV.

Abstract

After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that might explain the present discrepancy with the experimental value. None of them seems likely. In particular, a hypothetical increase of the hadroproduction cross section in low-energy e+e- collisions could bridge the muon g-2 discrepancy, but it is shown to be unlikely in view of current experimental error estimates. If, nonetheless, this turns out to be the explanation of the discrepancy, then the 95% CL upper bound on the Higgs boson mass is reduced to about 135GeV which, in conjunction with the experimental 114.4GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.