Dark Matter Search with the Nuclear Isomer Ta-180m

TL;DR

This paper explores using the rare isotope Ta-180m to detect or constrain exotic dark matter interactions through direct detection experiments and geochemical analysis, offering a novel approach beyond traditional WIMP searches.

Contribution

It introduces a new method employing nuclear isomers, specifically Ta-180m, for dark matter detection, providing constraints on dark matter models with less resource-intensive experiments.

Findings

Set new limits on dark matter interactions with Ta-180m.

Proposed an indirect geochemical detection method for long-term decay signatures.

Demonstrated the feasibility of using nuclear isomers in dark matter searches.

Abstract

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. $^{180m}$Ta is the rarest known isotope with the longest-lived meta-stable state whose partial half-life limits are on the order of 10$^{14}$-10$^{16}$ yr. We investigate how strongly interacting dark matter and inelastic dark dark matter collides with $^{180m}$Ta, 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 which has further constrained the open parameter space. We also propose an indirect geochemical experiment to search for decay products of $^{180m}$Ta in tantalum minerals accumulated over 1 billion years.