The muon g-2 discrepancy: errors or new physics?

TL;DR

This paper reviews the muon g-2 anomaly, evaluates potential errors in Standard Model predictions, and explores the implications of possible explanations, including their impact on Higgs boson mass constraints.

Contribution

It critically assesses hypothetical errors in Standard Model calculations and their plausibility in explaining the muon g-2 discrepancy, and discusses implications for Higgs mass bounds.

Findings

Standard Model errors unlikely to explain the discrepancy

Increasing hadroproduction cross section is inconsistent with current data

If explained by errors, Higgs mass upper bound reduces to about 130 GeV

Abstract

After a brief review of the muon g-2 status, we discuss hypothetical errors in the Standard Model prediction that could explain the present discrepancy with the experimental value. None of them looks likely. In particular, an hypothetical increase of the hadroproduction cross section in low-energy e^+e^- collisions could bridge the muon g-2 discrepancy, but 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 130 GeV which, in conjunction with the experimental 114.4 GeV 95% CL lower bound, leaves a narrow window for the mass of this fundamental particle.