Flavor alignment of New Physics in light of the $(g-2)_\mu$ anomaly

TL;DR

This paper explores how new physics models can explain the muon g-2 anomaly while respecting flavor constraints by analyzing operator alignment in the Standard Model Effective Field Theory through Renormalization Group mixing.

Contribution

It provides a detailed analysis of the flavor alignment conditions in SMEFT necessary for accommodating the muon g-2 anomaly within experimental bounds.

Findings

Semileptonic four-fermion operators must be tightly aligned with dipole operators.

Alignment conditions are crucial for new physics models to explain g-2 without violating flavor constraints.

Flavor symmetries or specific dynamics can help models meet these alignment requirements.

Abstract

Addressing the ${(g-2)_\mu}$ anomaly and simultaneously being consistent with the tight bounds on ${\mu \to e \gamma}$ requires a precise alignment of the lepton dipole operator in flavor space. We investigate this alignment condition in the Standard Model Effective Field Theory by considering the Renormalization Group mixing of the relevant operators. We find that semileptonic four-fermion operators, which are likely to yield a sizable contribution to the ${(g-2)_\mu}$ anomaly, need to be tightly aligned to the lepton dipole operator and Yukawa coupling. We discuss how New Physics models can comply with these stringent conditions by employing particular dynamical assumptions or using flavor symmetries.