Space-Based Measurement of the Neutron Lifetime using Data from the Neutron Spectrometer on NASA's MESSENGER Mission

TL;DR

This paper demonstrates the feasibility of measuring the neutron lifetime using space-based data from the MESSENGER spacecraft, offering an alternative method that could complement laboratory measurements and address existing discrepancies.

Contribution

It introduces a novel space-based approach to estimate neutron lifetime using cosmic-ray interactions, validated with data from NASA's MESSENGER mission.

Findings

Estimated neutron lifetime: 780±60(stat)±70(syst) seconds.

Proves space-based measurements can be used for fundamental particle parameters.

Supports the potential of future space missions for particle physics research.

Abstract

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 4$\sigma$. 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 $780\pm60_\textrm{stat}\pm70_\textrm{syst}$ s, thereby demonstrating the viability of this new approach.