Dark side of the neutron?

Abstract

We discuss our recently proposed interpretation of the discrepancy between the bottle and beam neutron lifetime experiments as a sign of a dark sector. The difference between the outcomes of the two types of measurements is explained by the existence of a neutron dark decay channel with a branching fraction 1%. Phenomenologically consistent particle physics models for the neutron dark decay can be constructed and they involve a strongly self-interacting dark sector. We elaborate on the theoretical developments around this idea and describe the efforts undertaken to verify it experimentally.

Electrodisintegration of Deuteron into Dark Matter and Proton Close to Threshold

“…Since, such a mechanism is far from being applicable to the analysis of the electrodisintegration of the deuteron, we will not discuss it in this paper. Another mechanism for the explanation of the NLA proposed by Berezhiani [24], assuming the existence of the neutron decays into dark matter particles, is similar to that by Fornal and Grinstein [1][2][3][4][5]. So our approach to the NLA seems to be a modification of both Berezhiani's, and Fornal and Grinstein's mechanism.…”

“…Recently, Fornal and Grinstein [1][2][3][4][5] proposed a solution to the neutron lifetime anomaly (NLA) problem, related to a discrepancy between experimental values of the neutron lifetime measured in bottle and beam experiments, through a contribution of the neutron dark matter decay mode n → χ + e − + e + , where χ is a dark matter fermion and (e − e + ) is the electron-positron pair. However, according to experimental data [6][7][8], the decay mode n → χ + e − + e + is suppressed.…”

Neutron’s dark secret

“…A possible strategy would be to install a proton detector in bottle experiments. 49 This idea is currently being implemented by the Los Alamos UCN collaboration within the project: "UCN measurement of the Proton branching ratio in neutron Beta decay" (UCNProBe). 50…”

Dark decay channel analysis (n → χ + e+ e−) with the PERKEO II experiment

“…Whereas the storage method measures the inclusive lifetime, the beta decay method (often called beam method) detects the partial lifetime for decay into a particular channel. The present 4σ discrepancy between the two results led Fornal and Grinstein [1,3,4] to propose different decay channels of the neutron involving a dark matter particle with no proton in the final state. These branches would have been missed by the most precise beta decay method experiments which have detected decay protons.…”