Is there a dark decay of neutrons in 6He ? E819S Data Analysis

by Marius Le Joubioux

The SPIRAL1 facility at GANIL was used in June 2021 to produce both ⁸He and ⁶He low energy beams in order to investigate the proposed exotic decay of neutrons into dark matter in the latter nucleus. We used the ⁸He decay scheme as a reference to test our detection setup. We computed the mean rate of implanted ⁸He with different observables. In this analysis we find that the mean rate values extracted from gamma ray at Eγ = 980.8keV in ⁸Li vary from one run to another between 1.4e5 and 4.6e5pps. Comparing the mean rate values between our neutron detector TETRA and the 980.8keV gamma we find that the former is in general 20% higher over the latter if we assume a general detection efficiency value measured with a ²⁵²Cf neutron source. Computing the proper mean rate of implanted particles with other detectors used during the experiment such as a silicium in the LIRAT line or the TI that measures the primary beam intensity on target is still being investigated and will be of great importance when analyzing ⁶He runs as we cannot rely on gamma-ray measurement.