Inelastic dark matter and strongly interacting dark matter are poorly constrained by direct detection experiments since they both require the scattering event to deliver energy from the nucleus into the dark matter in order to have observable effects. We propose to test these scenarios by searching for the collisional deexcitation of metastable nuclear isomers by the dark matter particles. The longevity of these isomers is related to a strong suppression of γ- and β-transitions, typically inhibited by a large difference in the angular momentum for the nuclear transition. The collisional deexcitation by dark matter is possible since heavy dark matter particles can have a momentum exchange with the nucleus comparable to the inverse nuclear size, hence lifting tremendous angular momentum suppression of the nuclear transition. This deexcitation can be observed either by searching for the direct effects of the decaying isomer, or through the rescattering or decay of excited dark matter states in a nearby conventional dark matter detector setup. Existing nuclear isomer sources such as naturally occurring Ta180m, Ba137m produced in decaying Cesium in nuclear waste, Lu177m from medical waste, and Hf178m from the Department of Energy storage can be combined with current dark matter detector technology to search for this class of dark matter.
Bibliographical noteFunding Information:
We would like to thank Bjoern Lehnert for useful explanations on the Tantalum decay experiment and Giovanni Benato for useful comments. M. P.’s research at Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Economic Development and Innovation. S. R. is supported in part by the NSF under Grant No. PHY-1638509, the Simons Foundation Grant No. 378243, and the Heising-Simons Foundation Grants No. 2015-038 and No. 2018-0765. H. R. is supported in part by the DOE under Contract No. DE-AC02-05CH11231. Some of this work was completed at the Aspen Center for Physics, which is supported by NSF Grant No. PHY-1607611. This research was supported in part by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence “Origin and Structure of the Universe.”