The possible explanation of neutron lifetime beam anomaly

TL;DR

This paper investigates the discrepancy between neutron lifetime measurements obtained via beam and storage methods, proposing proton loss due to charge exchange collisions as a key factor affecting beam experiment results.

Contribution

It offers a possible explanation for the neutron lifetime beam anomaly, highlighting proton loss mechanisms as a source of measurement discrepancy.

Findings

Storage method measurements are consistent with the Standard Model.

Beam method measurements show a significant discrepancy at 3.6σ.

Proton loss in magnetic traps may cause underestimation of neutron decay in beam experiments.

Abstract

The results of measurements performed using UCN storing method are in good agreement. The latest most accurate measurements of the neutron decay asymmetry and neutron lifetime measurements by storage method are in agreement within the Standard Model. However, there is a significant discrepancy at $3.6\sigma$ (1% of decay probability) level with beam method experiment. This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime with beam method experiment. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in a magnetic trap due to charge exchange collisions of protons with the residual gas. The proton becomes neutral and leaves the trap, which leads to a decrease in the number of registered protons, i.e. to a decrease in the probability of neutron decay or to an increase in the measured neutron lifetime.