A4 Article in conference proceedings
DM-like anomalies in neutron multiplicity spectra (2021)

Trzaska, W. H., Enqvist, T., Jedrzejczak, K., Joutsenvaara, J., Kasztelan, M., Kotavaara, O., Kuusiniemi, P., Loo, K.K., Orzechowski, J., Puputti, J., Slupecki, M., Szabelski, J., Usoskin, I., & Warda, T.E. (2021). DM-like anomalies in neutron multiplicity spectra. In TAUP 2021 : 17th International Conference on Topics in Astroparticle and Underground Physics (2156, Article 012029). IOP Publishing. Journal of Physics : Conference Series. https://doi.org/10.1088/1742-6596/2156/1/012029

JYU authors or editors

Publication details

All authors or editorsTrzaska, W. H.; Enqvist, T.; Jedrzejczak, K.; Joutsenvaara, J.; Kasztelan, M.; Kotavaara, O.; Kuusiniemi, P.; Loo, K.K.; Orzechowski, J.; Puputti, J.; et al.

Parent publicationTAUP 2021 : 17th International Conference on Topics in Astroparticle and Underground Physics

Place and date of conferenceOnline26.8.-3.9.2021

Journal or seriesJournal of Physics : Conference Series



Publication year2021

Publication date01/12/2021


Article number012029

PublisherIOP Publishing

Publication countryUnited Kingdom

Publication languageEnglish


Publication open accessOpenly available

Publication channel open accessOpen Access channel

Publication is parallel published (JYX)https://jyx.jyu.fi/handle/123456789/80033


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.

Keywordsparticle physicsdetectorsneutronsdark matter

Contributing organizations

Ministry reportingYes

Reporting Year2021

JUFO rating1

Last updated on 2024-22-04 at 19:47