Physics of our days

Disagreement between measurements of the neutron lifetime by the ultracold neutron storage method and the beam technique

The National Research Center "Kurchatov Institute", Konstantinov Petersburg Nuclear Physics Institute, Orlova Roshcha, Gatchina, Leningradskaya Region, 188300, Russian Federation

Recent measurements of neutron lifetime performed using a gravitational trap of ultracold neutrons (UCNs) (Konstantinov Petersburg Nuclear Physics Institute, Russia) and a magnetic UCN trap (LANL, USA) have confirmed PNPI's result of 2005. The results of the experiments with stored UCNs agree with each other but differ from those of the beam experiment (NIST, USA) by 3.5$\sigma$ (corresponding to 1% in the decay probability). This disagreement is currently discussed in the literature as a 'neutron anomaly'. We analyze possible reasons for that disagreement and test the experimental data for the neutron lifetime and beta-decay asymmetry within the Standard model. The test is only passed for the neutron lifetime values that are obtained using the UCN storage method.

Fulltext is available at IOP
Keywords: neutron lifetime, particle physics, dark matter
PACS: 06.20.−f, 12.60.−i, 14.20.Dh (all)
DOI: 10.3367/UFNe.2018.11.038475
Citation: Serebrov A P "Disagreement between measurements of the neutron lifetime by the ultracold neutron storage method and the beam technique" Phys. Usp. 62 596–601 (2019)
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Received: 13th, April 2018, revised: 2nd, November 2018, 15th, November 2018

Оригинал: Серебров А П «Разногласие между методом хранения ультрахолодных нейтронов и пучковым методом при измерении времени жизни нейтрона» УФН 189 635–641 (2019); DOI: 10.3367/UFNr.2018.11.038475

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