Space-based Measurements of Neutron Lifetime: Approaches to Resolving the Neutron Lifetime Anomaly

TL;DR

This paper explores space-based methods for measuring neutron lifetime to resolve existing discrepancies, proposing feasible experiments from Venus, Earth, and the Moon with potential to improve precision significantly.

Contribution

It introduces a dedicated space-based experimental approach for neutron lifetime measurement, analyzing various scenarios and their potential precision and feasibility.

Findings

Venus orbit measurements can achieve 3-second precision in less than a day.

Venus orbit can reach 1-second precision in under a week.

Earth orbit and lunar surface measurements are feasible within 40 to 300 days.

Abstract

Free neutrons have a measured lifetime of 880 s, but disagreement between existing laboratory measurements of ~10 s have persisted over many years. This uncertainty has implications for multiple physics disciplines, including standard-model particle physics and Big-Bang nucleosynthesis. Space-based neutron lifetime measurements have been shown to be feasible using existing data taken at Venus and the Moon, although the uncertainties for these measurements of tens of seconds prevent addressing the current lifetime discrepancy. We investigate the implementation of a dedicated space-based experiment that could provide a competitive and independent lifetime measurement. We considered a variety of scenarios, including measurements made from orbit about the Earth, Moon, and Venus, as well as on the surface of the Moon. For a standard-sized neutron detector, a measurement with three-second statistical precision can be obtained from Venus orbit in less than a day; a one-second statistical precision can be obtained from Venus orbit in less than a week. Similarly precise measurements in Earth orbit and on the lunar surface can be acquired in less than 40 days (three-second precision) and ~300 days (one-second precision). Systematic uncertainties that affect a space-based neutron lifetime measurement are investigated, and the feasibility of developing such an experiment is discussed.