ステライルニュートリノ、物理の基礎と異常な結果の解釈 Sterile neutrino, physics fundamentals among interpretations of anomalous results
2022-06-16 アメリカ・ロスアラモス国立研究所(LANL)
＜関連情報＞
- https://discover.lanl.gov/news/0616-best-experiment-results
- https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.232501
バクザン無菌化実験（BEST）の成果 Results from the Baksan Experiment on Sterile Transitions (BEST)
V. V. Barinov et al.
Physical Review Letters Published 9 June 2022
DOI:https://doi.org/10.1103/PhysRevLett.128.232501
ABSTRACT
The Baksan Experiment on Sterile Transitions (BEST) was designed to investigate the deficit of electron neutrinos νe observed in previous gallium-based radiochemical measurements with high-intensity neutrino sources, commonly referred to as the “gallium anomaly,” which could be interpreted as evidence for oscillations between νe and sterile neutrino (νs) states. A 3.414-MCi 51Cr νe source was placed at the center of two nested Ga volumes and measurements were made of the production of 71Ge through the charged current reaction, 71Ga(νe,e−)71Ge, at two average distances. The measured production rates for the inner and the outer targets, respectively, are [54.9+2.5−2.4(stat)±1.4(syst)] and [55.6+2.7−2.6(stat)±1.4(syst)] atoms of 71Ge/d. The ratio (R) of the measured rate of 71Ge production at each distance to the expected rate from the known cross section and experimental efficiencies are Rin=0.79±0.05 and Rout=0.77±0.05. The ratio of the outer to the inner result is 0.97±0.07, which is consistent with unity within uncertainty. The rates at each distance were found to be similar, but 20%–24% lower than expected, thus reaffirming the anomaly. These results are consistent with νe→νs oscillations with a relatively large Δm2 (>0.5 eV2) and mixing sin22θ (≈0.4).
