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#### Improved limits on the weak, neutral, hadronic axial vector coupling constants from quasielastic scattering of polarized electrons.

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##### Citation

Heil, W., Ahrens, J., Andresen, H. G., Bornheimer, A., Conrath, D., Dietz, K. J., et al. (1989).
Improved limits on the weak, neutral, hadronic axial vector coupling constants from quasielastic scattering of polarized electrons.* Nuclear Physics B,* *327*(1), 1-31. doi:10.1016/0550-3213(89)90284-8.

Cite as: http://hdl.handle.net/11858/00-001M-0000-002C-278B-9

##### Abstract

In scattering polarized electrons (P1 = 44% by 9Be at an energy of 300 MeV at angles 115°⩽ϑ⩽145° a parity violating asymmetry of Acorr = (−3.5 ± 0.7 ± 0.2) × 10−6 was measured. After correction for finite electron polarization and background we deduce an experimental asymmetry of Acx = (−9.4 ± 1.8 ± 0.5) × 10−6. The quoted errors indicate the statistical and the systematic uncertainties, respectively. The asymmetry, which is dominated by the quasielastic cross section, is interpreted in terms of model-independent electron-nucleon coupling constants of the weak neutral current. The error limits in the sector of axial vector coupling constants have been improved by a factor of 3 over previous results. A model-dependent analysis for the Weinberg angle yields the result sin2θw = 0.221 ± 0.014 ± 0.004.