University of Oulu

W. H. Trzaska et al 2021 J. Phys.: Conf. Ser. 2156 012029

DM-like anomalies in neutron multiplicity spectra

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Author: Trzaska, W. H.1; Enqvist, T.1; Jedrzejczak, K.2;
Organizations: 1Department of Physics, University of Jyväskylä, P.O. Box 35, FI-40014 University of Jyväskylä, Finland
2Cosmic Ray Laboratory, National Centre for Nuclear Research (NCBJ), 28 Pułku Strzelców Kaniowskich 69, 90-558 Łódź, Poland
3University of Oulu, Kerttu Saalasti Institute, Pajatie 5, 85500 Nivala, Finland
4Institut für Physik (IPH), Johannes Gutenberg-Universität Mainz (JGU), Staudingerweg 7, 55128 Mainz, Germany
5Helsinki Institute of Physics (HIP), P.O. Box 64, 00014 University of Helsinki, Finland
6University of Oulu, Sodankylä Geophysical Observatory, P.O. Box 3000, FIN- 99600 Sodankylä, Finland
7Office of Nuclear Energy, DOE 1000 Independence Ave., SW, Washington, D.C., 20585, United States
8TechSource, Santa Fe, NM, United States
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 3.8 MB)
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Language: English
Published: IOP Publishing, 2021
Publish Date: 2022-03-24


A new experiment collects data, since November 2019, at a depth of 210 m.w.e. in the Callio Lab in the Pyhasalmi mine in Finland. The setup, called NEMESIS (New Emma MEasurementS Including neutronS), incorporates infrastructure from the EMMA experiment with neutron and large-area plastic scintillator detectors. The experiment’s primary aim is to combine muon tracking with position-sensitive neutron detection to measure precision yields, multiplicities, and lateral distributions of high-multiplicity neutron events induced by cosmic muons in various materials. The data are relevant for background evaluation of the deep-underground searches for Dark Matter (DM), neutrino-less double beta decay, etc. Preliminary analysis revealed anomalies in muon-suppressed neutron multiplicity spectra collected during a 344-day run (live time) with a 565 kg Pb target. The spectra, otherwise well described by an exponential fit, show three peaks at high multiplicities. Although still at a low statistical significance, these small excesses match the outcome of an earlier measurement. The nature of the anomalies remains unclear, but, in principle, they may be a signature of self-annihilation of a WIMP with a mass close to 13 GeV/c2. With that assumption, the expected cross-section would be around 10−42 cm² for Spin-Dependent or 10‐46 cm² for Spin Independent interactions. We propose verifying this hypothesis with an upgraded NEMESIS experiment, able to collect an order of magnitude more data than this measurement. Based on the statistical uncertainty, analysis of the event rate indicates that cross-section limits for DM mass range of approximately 3‐40 GeV/c² can be investigated with such a setup.

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Series: Journal of physics. Conference series
ISSN: 1742-6588
ISSN-E: 1742-6596
ISSN-L: 1742-6588
Volume: 2156
Article number: 012029
DOI: 10.1088/1742-6596/2156/1/012029
Host publication: 17th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2021), 26 August-3 September 2021, Online
Conference: International Conference on Topics in Astroparticle and Underground Physics
Type of Publication: A4 Article in conference proceedings
Field of Science: 115 Astronomy and space science
Copyright information: Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.