Probing the electromagnetic properties of the neutrinos at future lepton colliders

Abstract

In this study, we explore the non-standard νν¯γγ couplings parametrized by dimension-seven operators via e+e−→νν¯γ process at the FCC-ee/CEPC and μ+μ−→νν¯γ process at the Muon Colliders. For the detailed Monte Carlo simulation, all signal and relevant background events are produced within the framework of Madgraph where non-standard νν¯γγ couplings are implemented. After passing through Pythia for parton showering and hadronization, detector effects are included via tuned corresponding detector cards for each collider in Delphes. Projected sensitivities on νν¯γγ couplings are obtained at a 5σ confidence level without and with 5% systematic uncertainties for the FCC-ee/CEPC and the Muon Colliders, showcasing the complementarity between lepton colliders. Our best limit on the anomalous νν¯γγ couplings even with 5% systematic uncertainties for muon collider with s=10 TeV and Lint=10 ab−1 are found to be fourteen orders of magnitude stronger than the upper bound obtained from rare decay Z→γγνν¯ analysis using LEP data.