Journal
PHYSICS LETTERS B
Volume 720, Issue 4-5, Pages 399-404Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.physletb.2013.02.033
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Funding
- Natural Sciences and Engineering Research Council (NSERC) of Canada
- Government of Canada through Industry Canada
- Province of Ontario through the Ministry of Research and Information (MRI)
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The rate of the direct decay of K-40 to the ground state of Ar-40 through electron capture has not been experimentally reported. Aside from its inherent importance for the theory of electron capture as the only such decay known of its type (unique third-forbidden), this decay presents an irreducible background in the DAMA experiment. We find that the presence of this background, as well as others, poses a challenge to any interpretation of the DAMA results in terms of a Dark Matter model with a small modulation fraction. A 10 ppb contamination of natural potassium requires a 20% modulation fraction or more. A 20 ppb contamination, which is reported as an upper limit by DAMA, disfavors any Dark Matter origin of the signal. This conclusion is based on the efficiency of detecting K-40 decays as inferred from simulation. We propose measures to help clarify the situation. (c) 2013 Elsevier B.V. All rights reserved.
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