Weinberg angle
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The Weinberg angle or weak mixing angle is a parameter in the Abdus Salam theory of the electroweak force. It gives a relationship between the W- and Z-masses, as well as the ratio of Z-Boson mediated interaction which behaves like a photon, i.e. its mixing. The weak mixing angle is denoted by the symbol θW, but in practice the quantity sin2(θW) is far more frequently used than θW itself.
The value of θW varies as a function of the momentum transfer, Q, at which it is measured; this 'running' is a key prediction of the electroweak theory. The most precise measurements have been carried out in electron-positron collider experiments at a value of Q = 91.2 GeV/c, corresponding to the mass of the Z0 boson, MZ. The 2004 best estimate of sin2 θW(MZ) in the MS-bar scheme is 0.23120(15). Atomic parity violation experiments yield values for sin2 θW at smaller values of Q, below 0.01 GeV/c, but with much lower precision. In 2005 results were published from a study of parity violation in Møller scattering in which a value of sin2 θW = 0.2397(13) was obtained at Q = 0.16 GeV/c, establishing experimentally the 'running' of the weak mixing angle.
[edit] References and external links
[edit] Primary and secondary sources
- Particle Data Group, Review of Particle Physics
- E158: A Precision Measurement of the Weak Mixing Angle in Møller Scattering
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