Regular Article - Experimental Physics
First limits on double beta decays in Th
INFN-Laboratori Nazionali del Gran Sasso, 67100, Assergi, AQ, Italy
2 Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
3 Physics Department, Queen’s University, Kingston, ON, K7L 3N6, Canada
Accepted: 23 July 2020
Published online: 19 August 2020
As one of the primordial radioactive isotopes, mainly undergoes -decay with a half-life of years. However, it is also one of 35 double beta decay candidates in which the single -decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle were measured in a HPGe well-detector at the Gran Sasso Underground Laboratory with a total exposure of 3.25 gd.
We obtain half-life limits on all double beta decay modes of to excited states of on the order of years. For the most likely transition into the 0 state we find a lower half-life limit of years (90% C.I.). These are the first constraints on double beta decay excited state transition in .
© The Author(s), 2020