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

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.