Probing the tau lepton magnetic moment at future lepton colliders

The anomalous magnetic moments of leptons are excellent candidates not only to test the Standard Model predictions, but also to investigate possible new physics effects. The long-standing discrepancy between the Standard Model prediction and the experimental measure of the muon g - 2 motivates the study of non-standard effects also in the electron and tau g - 2. In our work, we show the potential sensitivity of future lepton colliders (FCC-ee or a high-energy Muon Collider) to probe the tau g - 2. We point out that these facilities can generate processes like the radiative Higgs decay h -> tau(+)tau(-)gamma or the Drell-Yan processes l(+)l(-) -> tau(+)tau(-)(h) enabling to test the tau g - 2 with a resolution of O(10(-5) - 10(-4)) that is orders of magnitude better than the current LEP sensitivity.