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Space-based measurement of the neutron lifetime using data from the neutron spectrometer on NASA's MESSENGER mission.

Wilson, Jack T. and Lawrence, David J. and Peplowski, Patrick N. and Eke, Vincent R. and Kegerreis, Jacob A. (2020) 'Space-based measurement of the neutron lifetime using data from the neutron spectrometer on NASA's MESSENGER mission.', Physical review research., 2 (2). 023316.


We establish the feasibility of measuring the neutron lifetime via an alternative, space-based class of methods, which use neutrons generated by galactic cosmic ray spallation of planets surfaces and atmospheres. Free neutrons decay via the weak interaction with a mean lifetime of around 880 s. This lifetime constrains the unitarity of the CKM matrix and is a key parameter for studies of Big-Bang nucleosynthesis. However, current laboratory measurements, using two independent approaches, differ by over 4σ. Using data acquired in 2007 and 2008 during flybys of Venus and Mercury by NASA’s MESSENGER spacecraft, which was not designed to make this measurement, we estimate the neutron lifetime to be 780 ± 60stat ± 70syst s, thereby demonstrating the viability of this new approach.

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Publisher statement:Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Date accepted:06 May 2020
Date deposited:12 June 2020
Date of first online publication:11 June 2020
Date first made open access:12 June 2020

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