Search for dark matter induced de-excitation of $^{180}$Ta$\rm ^m$

Understand

Weak-scale dark matter particles, in collisions with nuclei, can mediate transitions between different nuclear energy levels.

• In particular, owing to sizeable momentum exchange, dark matter particles can enable de-excitation of nuclear isomers that are extremely long lived with respect to regular radioactive decays.
• In this paper, we utilize data from a past experiment with $^{180}$Ta$\rm ^m$ to search for $\gamma$-lines that would accompany dark matter induced de-excitation of this isomer.
• Non-observation of such transitions above background yields the first direct constraint on the lifetime of $^{180}$Ta$\rm ^m$ against DM-initiated transitions: $T_{1/2}>1.3\times 10^{14}$~a at 90\% C.I.