Colliding light to measure tau g–2

Measurements of the electron and muon anomalous magnetic moments (g–2) are cornerstones of fundamental physics. Reaching 13 and 10 decimal place precision, respectively, they are among the most precisely measured quantities in nature with tantalizing sensitivity to new physics. But what the tau-lepton? Tau g–2 is poorly constrained due to its short lifetime, known to only constrained to 2 decimal places and experimental progress stalled after LEP. Innovative strategies proposed for the LHC are triggering renewed interest in tau g–2. Recent advances in unconventional tracking open the LHC observation of tau-leptons produced in photon collisions. Overlooked in its original program, this introduces important electromagnetic dipole physics to hadron colliders with tau g–2 surpassing LEP precision that stood for two decades.