New physics behind the new muon $g$-2 puzzle?

TL;DR

This paper investigates whether new physics could explain the discrepancy in muon g-2 measurements by affecting the hadronic cross-section, but finds that experimental constraints exclude this possibility.

Contribution

It explores the hypothesis that new physics modifies the e+e- hadronic cross-section to resolve the muon g-2 puzzle, and demonstrates this is inconsistent with existing experimental data.

Findings

New physics contribution to e+e- cross-section cannot resolve the muon g-2 discrepancy.

Experimental constraints exclude the proposed new physics solution.

The tension between lattice QCD results and experimental data remains unresolved.

Abstract

The recent measurement of the muon $g$-2 at Fermilab confirms the previous Brookhaven result. The leading hadronic vacuum polarization (HVP) contribution to the muon $g$-2 represents a crucial ingredient to establish if the Standard Model prediction differs from the experimental value. A recent lattice QCD result by the BMW collaboration shows a tension with the low-energy $e^+e^- \to \text{hadrons}$ data which are currently used to determine the HVP contribution. We refer to this tension as the new muon $g$-2 puzzle. In this Letter we consider the possibility that new physics contributes to the $e^+e^- \to \text{hadrons}$ cross-section. This scenario could, in principle, solve the new muon $g$-2 puzzle. However, we show that this solution is excluded by a number of experimental constraints.