Refined determination of the weak mixing angle at low energy
arxiv(2024)
摘要
The weak mixing angle is a fundamental parameter of the electroweak theory of
the standard model whose measurement in the low-energy regime is still not
precisely determined. Different probes are sensitive to its value, among which
atomic parity violation, coherent elastic neutrino-nucleus scattering and
parity-violating electron scattering on different nuclei. In this work, we
attempt for the first time to combine all these various determinations by
performing a global fit that also keeps into account the unavoidable dependence
on the experimentally poorly known neutron distribution radius of the nuclei
employed, for which a new measurement using proton-cesium elastic scattering
became available. By using all present direct determinations of the neutron
distribution radius of cesium we find sin^2ϑ_W
=0.2396^+0.0020_-0.0019, which should supersede the previous value
determined from atomic parity violation on cesium. When including electroweak
only, but also indirect, determinations of the neutron distribution radius of
cesium the uncertainty reduces to 0.0017 maintaining the same central value,
showing an excellent agreement independently of the method used.
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