Probing the Tau Neutrino Magnetic Moment via the $μ^{-}γ\rightarrow μ^{-}ν\barν$ Process at Future Muon Colliders

Abstract

We investigate the sensitivity of future muon colliders to the anomalous magnetic moment of the tau neutrino within a model-independent effective field theory framework. The analysis is performed through the subprocess $μ^{-}γ\rightarrow μ^{-}ν\barν$ where the initial-state photon is described using the Equivalent Photon Approximation. Signal and background events are generated with MadGraph5$\_$aMC$@$NLO, followed by parton showering and hadronization with PYTHIA8. Detector effects are simulated using DELPHES3, while the event reconstruction and analysis are carried out via the MadAnalysis5 framework. Optimized kinematic selection criteria are determined for center-of-mass energies of 3, 10 and 30 TeV muon colliders. The expected sensitivities are evaluated using the Asimov significance method. The best sensitivity is obtained for the 30 TeV muon collider option, where the anomalous magnetic moment of the tau neutrino can be probed down to $μ_{ττ}=5.21\times10^{-8}\,μ_B$ at the 5$σ$ significance level assuming a 1\% systematic uncertainty. Our sensitivity bounds improve the current direct experimental limit reported by the DONUT Collaboration up to one order of magnitude and demonstrate the strong potential of future muon colliders for probing neutrino electromagnetic interactions.