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Published August 19, 2005 | Published
Journal Article Open

Precision measurement of the weak mixing angle in Møller scattering


We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: A_PV = [-131 ± 14(stat) ± 10(syst)] × 10^-9, leading to the determination of the weak mixing angle sin^(2)Θ^(eff)(_W) = 0.2397 ± 0.0010(stat) ± 0.0008(syst), evaluated at Q^2 = 0.026  GeV^2. Combining this result with the measurements of sinΘ^(2)θ^(eff)(_W) at the Z^0 pole, the running of the weak mixing angle is observed with over 6σ significance. The measurement sets constraints on new physics effects at the TeV scale.

Additional Information

© 2005 American Physical Society. Received 26 April 2005; published 17 August 2005. We thank the SLAC staff for their efforts in helping develop and operate the E158 apparatus, and especially the Polarized Electron Source and Accelerator Operations groups.We would also like to thank A. Czarnecki, J. Erler, W. J. Marciano, and M. Ramsey-Musolf for stimulating discussions, and A. Ilyichev, J. Suarez, and V. Zykunov for providing the radiative correction software. This work was supported by Department of Energy Contract No. DEAC02- 76SF00515, and by the Division of Nuclear Physics at the Department of Energy and the Nuclear Physics Division of the National Science Foundation in the United States and the Commissariat à l'Énergie Atomique and the Centre National de la Recherche Scientifique in France.

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