Measurement of the running of the fine-structure constant

Small-angle Bhabha scattering data recorded at the Z resonance and large-angle Bhabha scattering data recorded at s=189GeV by the L3 detector at LEP are used to measure the running of the effective fine-structure constant for spacelike momentum transfers. The results areα−1(−2.1GeV2)−α−1(−6.25GeV2)=0.78±0.26α−1(−12.25GeV2)−α−1(−3434GeV2)=3.80±1.29,in agreement with theoretical predictions.