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

Understand

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.