The QED processes e+e- → e+e-μ+μ- and e+e- → e+e-τ+τ- are studied with the L3 detector at LEP using an untagged data sample collected at centre-of-mass energies 161 GeV ≤ √s ≤ 209 GeV. The τ-pairs are observed through the associated decay of one τ into eνν and the other into ππν. The cross sections are measured as a function of √s. For muon pairs, the cross section of the γγ → μ+μ- process is also measured as a function of the two-photon centre-of-mass energy for 3 GeV ≤ Wγγ ≤ 40 GeV. Good agreement is found between these measurements and the O(α4) QED expectations. In addition, limits on the anomalous magnetic and electric dipole moments of the τ lepton are extracted.
|Number of pages||10|
|Journal||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|State||Published - 8 Apr 2004|