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Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP
(2005)Physics Letters BThe evolution of the electromagnetic coupling, α, in the momentum-transfer range 1800 GeV2 < -Q2 < 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies √s = 189-209 GeV. The running of α is parametrised as: α(Q2) = α0/1 - C Δα(Q2), where α ≡ α(Q2 = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential ...Journal Article -
Neutral-current four-fermion production in e+e- interactions at LEP
(2005)Physics Letters BNeutral-current four-fermion production, e+e -→ff̄f′f̄′, is studied in 0.7 fb -1 of data collected with the L3 detector at LEP at centre-of-mass energies s=183-209 GeV. Four final states are considered: qq̄νν̄ , qq̄ℓ+ℓ-, ℓ+ℓ-ℓ′+ℓ′- and ℓ+ℓ-νν̄, where ℓ denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e+e-→Zγ *→ff̄f′f̄′ process is studied and ...Journal Article