Abstract
The Qweak experiment at the Thomas Jefferson National Accelerator Facility measures the parity violating asymmetry in longitudinally polarized electron scattering from the proton at very low momentum transfer, Q 2 = 0.026 (GeV/c)2, at an incident electron beam energy of 1.16 GeV. With this measurement and the earlier results of the parity violating elastic scattering experiments, the Qweak experiment determines the weak charge of the proton, \({Q^p_{\rm W}}\), with a 4% combined statistical and systematic error. This measurement will be used to determine the weak mixing angle, \({\sin^2\theta_{\rm W}}\), that is predicted by the Standard Model from the Z 0 pole down to lower energies. Qweak will determine \({\sin^2\theta_{\rm W}}\) to a 0.3% relative precision, providing a competitive measurement of the running of this quantity. Moreover, if there is a significant deviation of the weak mixing angle from the Standard Model prediction, then the Qweak experiment will give a glimpse of possible extensions of the Standard Model.
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References
Prescott C.Y. et al.: Parity non-conservation in inelastic electron scattering. Phys. Lett. B 77, 347–352 (1978). doi:10.1016/0370-2693(78)90722-0
Armstrong, D.S., et al.: The Qweak Experiment. PAC Proposal Update JLab E02-020 (2007). http://qweak.jlab.org/doc-public/ShowDocument?docid=703. Accessed June 2011
Erler J., Kurylov A., Ramsey-Musolf M.J.: Weak charge of the proton and new physics. Phys. Rev. D 68, 016006 (2003). doi:10.1103/PhysRevD.68.016006
Young R.D., Carlini R.D., Thomas A.W., Roche J.: Testing the standard model by precision measurement of the weak charges of quarks. Phys. Rev. Lett. 99, 122003 (2007). doi:10.1103/PhysRevLett.99.122003
Erler J., Ramsey-Musolf M.J.: Low energy tests of the weak interaction. Prog. Part. Nucl. Phys. 54, 351 (2005). doi:10.1016/j.ppnp.2004.08.001
Yao W.M. et al.: Review of particle physics. J. Phys. G 33, 1 (2006). doi:10.1088/0954-3899/33/1/001
Nakamura K. et al.: Review of particle physics. J. Phys. G 37, 075021 (2010). doi:10.1088/0954-3899/37/7A/075021
Erler J., Ramsey-Musolf M.J.: Weak mixing angle at low energies. Phys. Rev. D 72, 073003 (2005). doi:10.1103/PhysRevD.72.073003
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Lee, J.H., The Qweak Collaboration. The Qweak: Precision Measurement of the Proton’s Weak Charge by Parity Violating Experiment. Few-Body Syst 54, 129–134 (2013). https://doi.org/10.1007/s00601-012-0339-9
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DOI: https://doi.org/10.1007/s00601-012-0339-9