Measurement of the Electromagnetic Coupling at Large Momentum Transfer

Publisher Website

20 January 1997

journal article
research article
Published by American Physical Society (APS) in Physical Review Letters

Vol. 78 (3) , 424-427
https://doi.org/10.1103/physrevlett.78.424

Abstract

We report the first purely electroweak measurement of the strengthening of the electromagnetic coupling,

α_{QED}

with increasing momentum transfer

Q^{2}

, by comparing the process

e^{+} e^{-} \to μ^{+} μ^{-}

with the process

e^{+} e^{-} \to e^{+} e^{-} μ^{+} μ^{-}

. The data were accumulated at an average center-of-mass energy

〈 \sqrt{s} 〉 = 57.77 GeV

using the TOPAZ detector at the TRISTAN

e^{+} e^{-}

collider. We measure

α_{QED}^{- 1} (Q^{2}

) to change from its known value of

α_{QED}^{- 1} ≅ 137.0

at

Q^{2} = 0 to 128.5 \pm 1.8 (stat) \pm 0.7 (syst)

at

Q^{2} = (57.77 GeV / c)^{2}

. This result agrees with electroweak predictions.

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