Generalized Lomb-Scargle analysis of $\rm{^{90}Sr/^{90}Y}$ decay rate measurements from the Physikalisch-Technische Bundesanstalt

TL;DR

This study applies the generalized Lomb-Scargle periodogram to decay rate data of Sr/Y from PTB, confirming an ~11/year oscillation with moderate significance, addressing previous disputes.

Contribution

It provides a rigorous analysis confirming periodicity in decay rates using two error models and bootstrap significance testing, clarifying prior conflicting claims.

Findings

Evidence for ~11/year periodicity in decay data

Oscillation detected in two of three samples

Lower significance than previous claims

Abstract

We apply the generalized Lomb-Scargle (LS) periodogram to independently confirm the claim by Sturrock et al (arXiv:1605.03088) of oscillation at a frequency of 11/year in the decay rates of $\rm{^{90}Sr/^{90}Y}$ from measurements at the Physikalisch Technische Bundesanstalt (PTB), which however has been disputed by Kossert and Nahle (arXiv:1407.2493). For this analysis, we made two different {\it ansatze} for the errors. For each peak in the LS periodogram, we evaluate the statistical significance using non-parametric bootstrap resampling. We find using both of these error models evidence for ~11/year periodicity in the $\rm{^{90}Sr/^{90}Y}$ data for two of the three samples, but at a lower significance than that claimed by Sturrock et al.