Electron and muon magnetic moments search for New Physics ⚡ экспресс
A quantity a_{μ-e} = a_μ − (m_μ/m_e)² a_e is introduced — a linear combination of the anomalous magnetic moments of the muon and electron. Due to scaling, the short-distance contributions cancel exactly, improving ultraviolet behavior and avoiding problems inherent to separate a_μ or a_e. The hadronic vacuum polarization contribution to a_{μ-e} and its uncertainty are reduced by about 85% compared to a_μ. This opens prospects for testing New Physics with partial violation of lepton flavor universality, as well as for flavor-universal states at the sub-GeV scale, provided experimental measurements of a_e and α are significantly improved.
Electrons and muons are tiny magnets. Their magnetism is slightly more than two (in special units), and this 'excess fraction' (anomalous magnetic moment) arises from constant ripples in the vacuum: particle pairs momentarily pop into existence and vanish. For the muon—the heavy cousin of the electron—this excess is more noticeable, meaning it senses the unknown more keenly.
The trick is to combine the readings of the electron and muon so that the main interference—from the strong interactions that glue the nucleus—cancels out. Like a radio receiver: noise fades, and a clean signal emerges. The remainder points to new particles or forces. Uncertainty drops by 85%.
The problem: we need jeweler's precision in measuring the electron's extra bit. Experimenters are already at work. It was started by Julian Schwinger in 1948, and now measurement precision has skyrocketed millions of times.
🎯 The muon is about 207 times heavier than the electron but lives only 2.2 microseconds—a true mayfly of the microworld.