Abstract
The possibility of relatively fast neutron oscillations into a mirror neutron state is not excluded experimentally when a mirror magnetic field is considered. Direct searches for the disappearance of neutrons into mirror neutrons in a controlled magnetic field have previously been performed using ultracold neutrons, with some anomalous results reported. We describe a technique using cold neutrons to perform a disappearance and regeneration search, which would allow us to unambiguously identify a possible oscillation signal. An experiment using the existing General Purpose-Small Angle Neutron Scattering instrument at the High Flux Isotope Reactor at Oak Ridge National Laboratory will have the sensitivity to fully explore the parameter space of prior ultracold neutron searches and confirm or refute previous claims of observation. This instrument can also conclusively test the validity of recently suggested oscillation-based explanations for the neutron lifetime anomaly.
Highlights
The astrophysical evidence for dark matter is strong
The General Purpose Small Angle Neutron Scattering (GP-SANS) instrument at the 85 MW High Flux Isotope Reactor (HFIR) [16] has been identified as a promising experimental setup for mirror neutron oscillation searches, with intensities of order 1010 n/s between 4–25 Aexpected to be available when operated in white beam mode (Fig. 1)
We have identified three types of neutron-mirror neutron oscillation searches that can be performed at GP-SANS, which we briefly summarize here
Summary
Despite decades of searches, we still do not know what the particle nature of dark matter is. In identifying other potential explanations for gravitational observations, a common strategy is to link the dark matter to other questions or anomalies in particle physics. The neutron lifetime puzzle, the nearly 4 σ difference between the neutron lifetime measured using cold neutron and ultracold neutron techniques, has motivated searches for mirror and dark neutrons [2,3,4]. An improved search with ultracold neutrons projects a significantly improved sensitivity over this magnetic field range [13], and new ideas with cold neutron beams have been put forth that can resolve the ambiguity associated with the source of ultracold neutron losses [14, 15]
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