Investigation of the fundamental constants stability based on the reactor Oklo burn-up analysis

TL;DR

This study uses Monte Carlo simulations and isotope ratio analysis of the Oklo natural reactor to set new, tighter constraints on the possible variation of the fine structure constant over geological timescales.

Contribution

It introduces a novel approach combining isotope ratios and neutron spectrum reconstruction to improve limits on fundamental constant variations.

Findings

Limits on the change of the fine structure constant are tightened to |δα/α| ≤ 5×10⁻¹⁸.

Neutron spectrum and core temperature were accurately reconstructed from isotope ratios.

Discrepancies in neutron absorption cross sections help constrain resonance shifts.

Abstract

The burn-up for SC56-1472 sample of the natural Oklo reactor zone 3 was calculated using the modern Monte Carlo codes. We reconstructed the neutron spectrum in the core by means of the isotope ratios: $^{147}$Sm/$^{148}$Sm and $^{176}$Lu/$^{175}$Lu. These ratios unambiguously determine the spectrum index and core temperature. The effective neutron absorption cross section of $^{149}$Sm calculated using this spectrum was compared with experimental one. The disagreement between these two values allows to limit a possible shift of the low laying resonance of $^{149}$Sm even more . Then, these limits were converted to the limits for the change of the fine structure constant $\alpha$. We found that for the rate of $\alpha$ change the inequality $|\delta \dot{\alpha}/\alpha| \le 5\cdot 10^{-18}$ is fulfilled, which is of the next higher order than our previous limit.