Muon anomalous magnetic moment: Standard Model Theory

This is a short review of the current status of the Standard Model calculation of the Muon 𝑔 − 2 , based on the recently published White Paper. After a brief summary of the theoretically very well determined QED and electroweak contributions, the review focuses on the two main hadronic contributions, the vacuum polarization (HVP) and the light-by-light (HLbL), both for what concerns the lattice as well as the dispersive, data-driven determinations. In view of discrepancies in the data sets used for the dispersive determination of the HVP, the final theoretical value of the Muon 𝑔 − 2 in the SM is based on the lattice value for the HVP contribution and an average of the lattice and dispersive determinations for the HLbL contribution. The review ends with a brief outlook on how to address two urgent challenges: (i) reduce the theory uncertainty by a factor four to match the experimental one; (ii) resolve the current puzzles affecting data-driven determinations of the HVP contribution.