Production of e, μ and τ pairs in untagged two-photon collisions at LEP

The two-photon collision reaction e+e− → e+e−l+l− has been studied at 2≈91GeV using the L3 detector at LEP for l = e, μ, τ. We have analysed untagged configurations where the two photons are quasi-real. Good agreement is found between our measurements and the O(α4) QED expectation.