Dark Matter Search with the Nuclear Isomer Ta-180m

2 Sep 2021, 17:10
Talk in parallel session Dark Matter and its detection Discussion Panel Dark Matter 8


Bjoern Lehnert (Berkeley Lab)


There is compelling cosmological and astrophysical evidence of dark matter comprising 27% of the energy budget of the Universe. However, dark matter has never been observed in direct detection experiments. The long-time favorite model of Weakly Interacting Massive Particles saw a large experimental effort with steady progress over recent decades. Since also these large-scale searches remain unsuccessful to date, it is compelling to look at more exotic dark matter models which can be constrained with new approaches and much less scientific resources. Using nuclear isomers is one of these approaches.

Ta-180m is the rarest known isotope and the longest-lived meta-stable state whose half-life limits are on the order of $10^{16}$ yr. We investigate how strongly interacting dark matter collides with Ta-180m, leading to its de-excitation. The energy stored in the meta-stable state is released in the transition, which becomes the signature for thermalized dark matter in a well-shielded underground experiment.

We report on a direct detection experiment searching for these dark-matter-induced decay signatures. This search has further constrained open parameter space of cross-section, mass, and component fraction of strongly interacting dark matter. We also propose an indirect geological experiment to search for decay products of Ta-180m in tantalum minerals accumulated over 1 billion years.

Reference to paper (DOI or arXiv) https://dx.doi.org/10.1103/PhysRevLett.124.181802

Primary author

Bjoern Lehnert (Berkeley Lab)

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