Test of Lorentz invariance inβdecay of polarizedNa20

Abstract

Background: Lorentz invariance is key in our understanding of nature, yet relatively few experiments have tested Lorentz invariance in weak interactions.Purpose: Obtaining limits on Lorentz-invariance violation in weak interactions, in particular rotational invariance in β-decay. Method:We search for a dependence of the lifetime of 20 Na nuclei on the nuclear spin direction.Such directional dependence would be evidence for Lorentz-invariance violation in weak interactions. A difference in lifetime between nuclei that are polarized in the east and west direction is searched for. This difference is maximally sensitive to the rotation of the Earth, while the sidereal dependence is free from most systematic errors.Results: The experiment sets a limit of 2 × 10 −4 at 90 % C.L. on the amplitude of the sidereal variation of the relative lifetime differences, an improvement by a factor 15 compared to an earlier result.Conclusions: No significant violation of Lorentz invariance is found. The result sets limits on parameters of theories describing Lorentz-invariance violation.

Reflections on Wilczynski's Scientific Work in Groningen

“…A fascinating subject but outside the scope of this workshop. We give a few references here for those who may be interested [25][26][27].…”

Hadronic Lorentz violation in chiral perturbation theory including the coupling to external fields

“…The most recent direct search for anisotropy in β-decay examined the lifetime of 20 Na, decaying via a Gamow-Teller positron emission, looking at how that lifetime depended on the spin of the 20 Na nucleus, all while the terrestrial laboratory was rotating [21]. The experiment had sensitivity at the 4 × 10 −4 level to the imaginary parts of the coefficients χ µν EW (which are, unlike the quark coefficients, generally complex).…”

Electron capture beta decay of partially polarized nuclei

“…Electron capture beta decay of nuclei polarized by a strong hyperfine field in a ferromagnetic substance can be used as a compact source of directed mono-energetic neutrino radiation [1]. Such a device could be exploited in future neutrino communication [2,3],forthe measurement of the neutrino rest mass [4],and for testing of Lorentz invariance in beta decay [5]. Probably, the most appropriate nuclei for these objectives are 119 Sb with the nuclear spin I = 5/2, nuclear magnetic moment μ = 1.74x10 -26 J/T and half-life 1/2 T = 38.2 h[6-8].…”