Abstract
Measurements of the lifetime of neutrons trapped in a bottle have been consistently shorter than the lifetime measured in neutron beam experiments. With trapping potentials as low as 50 neV and neutron detectors located only at the top of the bottle, this discrepancy could be the result of the soft scattering of dark matter with neutrons. However, it is challenging to obtain the observed loss rate in conventional models of dark matter scattering. We show that this phenomenology is possible in composite models of dark matter where the soft scattering is from dark matter that has been captured and accumulated in the earth. This solution can be tested by placing more neutron detectors around the trap, providing better angular coverage. The phenomenology of soft scattering by trapped composite dark matter is generic and suggests new experimental directions that could be pursued to detect this large class of models.
Highlights
The lifetime of the neutron, a number of fundamental importance to big bang nucleosynthesis, has recently become a topic of contention
We explore the possibility that the loss of ultracold neutrons from the trap is due to scattering between neutrons and dark matter
We show that the required dark matter density and cross section that is consistent with all observational constraints can be realized in models of composite dark matter
Summary
The lifetime of the neutron, a number of fundamental importance to big bang nucleosynthesis, has recently become a topic of contention. We explore the possibility that the loss of ultracold neutrons from the trap is due to scattering between neutrons and dark matter. The loss of neutrons through energy exchange between them and the environment is a significant systematic in the trapped neutron experiments, and there are experimental checks on this possibility [2]. Lighter blobs will scatter off these heavier blobs and get captured Note that such a distribution in blob masses is to be expected in composite dark matter scenarios, since composite systems generically produce such a distribution during “blob nucleosynthesis.”. These blobs can undergo the soft scattering needed to explain the lifetime of the trapped neutrons. The neutron (or proton) is assumed to have a “dark electric dipole moment” with this vector
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