Spin effects in the tau-lepton pair induced by anomalous magnetic and electric dipole moments

Abstract

The possible anomalous New Physics contributions to magnetic and electric dipole moments of the $\tau$ lepton have brought renewed interest in studying $\tau$-pair production at energies of the LHC and future colliders. We discuss effects of electromagnetic and weak dipole moment contributions to the $\tau$-lepton polarization and $\tau \tau$ spin correlations in the $\gamma \gamma \to {\tau }^{-}{\tau }^{+}$ and $q\bar{q}\to {\tau }^{-}{\tau }^{+}$ processes. Such processes have been observed in $pp$ and PbPb collisions in the LHC experiments. Extensions of the Standard Model amplitudes for $\gamma \gamma \to {\tau }^{-}{\tau }^{+}$ and $q\bar{q}\to {\tau }^{-}{\tau }^{+}$ processes, which include dipole moments of the $\tau$ lepton, are implemented in the TauSpinner Monte Carlo program. A few examples of signatures of $\tau \tau$ spin correlations and $\tau$-lepton dipole moments in observables are presented.

Comments: 10 pages, 3 figures; contribution to Proceedings of the XLVI International Conference of Theoretical Physics "Matter to the Deepest", Katowice, Poland, 15-19 September, 2025