Probing anomalous γγγγ couplings at a future muon collider

We have studied anomalous four-photon couplings in the μ+μ−→μ+γγμ− scattering at a future muon collider. The collision energies of 3 TeV, 14 TeV, and 100 TeV are addressed. Both differential and total cross sections versus invariant mass of the outgoing photons are calculated. The best 95% C.L. exclusion bounds on anomalous couplings are obtained to be g1=2.23×10−8 TeV−4 and g2=4.22×10−8 TeV−4. They correspond to the muon collision energy of 100 TeV. The partial-wave unitary constraints on g1 and g2 are examined. We have demonstrated that the unitarity is not violated in a region of the anomalous couplings obtained in the present paper.