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1. Strong constraints from COSINE-100 on the DAMA dark matter results using the same sodium iodide target

   https://doi.org/10.1126/sciadv.abk2699  

   Adhikari, Govinda ; de Souza, Estella B. ; Carlin, Nelson ; Choi, Jae Jin ; Choi, Seonho ; Djamal, Mitra ; Ezeribe, Anthony C. ; França, Luis E. ; Ha, Chang Hyon ; Hahn, In Sik ; et al ( November 2021 , Science Advances)

   We present new constraints on dark matter interactions using 1.7 years of COSINE-100 data. The COSINE-100 experiment, consisting of 106 kg of tallium-doped sodium iodide [NaI(Tl)] target material, is aimed to test DAMA’s claim of dark matter observation using the same NaI(Tl) detectors. Improved event selection requirements, a more precise understanding of the detector background, and the use of a larger dataset considerably enhance the COSINE-100 sensitivity for dark matter detection. No signal consistent with the dark matter interaction is identified and rules out model-dependent dark matter interpretations of the DAMA signals in the specific context of standard halo modelmore »with the same NaI(Tl) target for various interaction hypotheses.« less
2. Background modeling for dark matter search with 1.7 years of COSINE-100 data

   https://doi.org/10.1140/epjc/s10052-021-09564-0  

   Adhikari, G. ; de Souza, E. Barbosa ; Carlin, N. ; Choi, J. J. ; Choi, S. ; Djamal, M. ; Ezeribe, A. C. ; França, L. E. ; Ha, C. ; Hahn, I. S. ; et al ( September 2021 , The European Physical Journal C)

   Abstract We present a background model for dark matter searches using an array of NaI(Tl) crystals in the COSINE-100 experiment that is located in the Yangyang underground laboratory. The model includes background contributions from both internal and external sources, including cosmogenic radionuclides and surface $$^{210}$$ 210 Pb contamination. To build the model in the low energy region, with a threshold of 1 keV, we used a depth profile of $$^{210}$$ 210 Pb contamination in the surface of the NaI(Tl) crystals determined in a comparison between measured and simulated spectra. We also considered the effect of the energy scale errors propagated frommore »the statistical uncertainties and the nonlinear detector response at low energies. The 1.7 years COSINE-100 data taken between October 21, 2016 and July 18, 2018 were used for this analysis. Our Monte Carlo simulation provides a non-Gaussian peak around 50 keV originating from beta decays of bulk $$^{210}$$ 210 Pb in a good agreement with the measured background. This model estimates that the activities of bulk $$^{210}$$ 210 Pb and $$^{3}$$ 3 H are dominating the background rate that amounts to an average level of $$2.85\pm 0.15$$ 2.85 ± 0.15  counts/day/keV/kg in the energy region of (1–6) keV, using COSINE-100 data with a total exposure of 97.7 kg $$\cdot $$ · years.« less
3. Recursive Sparse Representation for Identifying Multiple Concurrent Occupants Using Floor Vibration Sensing

   https://doi.org/10.1145/3517229  

   Fagert, Jonathon ; Mirshekari, Mostafa ; Zhang, Pei ; Noh, Hae Young ( March 2022 , Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies)

   In this paper, we present a multiple concurrent occupant identification approach through footstep-induced floor vibration sensing. Identification of human occupants is useful in a variety of indoor smart structure scenarios, with applications in building security, space allocation, and healthcare. Existing approaches leverage sensing modalities such as vision, acoustic, RF, and wearables, but are limited due to deployment constraints such as line-of-sight requirements, sensitivity to noise, dense sensor deployment, and requiring each walker to wear/carry a device. To overcome these restrictions, we use footstep-induced structural vibration sensing. Footstep-induced signals contain information about the occupants' unique gait characteristics, and propagate through themore »structural medium, which enables sparse and passive identification of indoor occupants. The primary research challenge is that multiple-person footstep-induced vibration responses are a mixture of structurally-codependent overlapping individual responses with unknown timing, spectral content, and mixing ratios. As such, it is difficult to determine which part of the signal corresponds to each occupant. We overcome this challenge through a recursive sparse representation approach based on cosine distance that identifies each occupant in a footstep event in the order that their signals are generated, reconstructs their portion of the signal, and removes it from the mixed response. By leveraging sparse representation, our approach can simultaneously identify and separate mixed/overlapping responses, and the use of the cosine distance error function reduces the influence of structural codependency on the multiple walkers' signals. In this way, we isolate and identify each of the multiple occupants' footstep responses. We evaluate our approach by conducting real-world walking experiments with three concurrent walkers and achieve an average F1 score for identifying all persons of 0.89 (1.3x baseline improvement), and with a 10-person "hybrid" dataset (simulated combination of single-walker real-world data), we identify 2, 3, and 4 concurrent walkers with a trace-level accuracy of 100%, 93%, and 73%, respectively, and observe as much as a 2.9x error reduction over a naive baseline approach.« less
4. An effective way to mark cohorts of juvenile terrestrial direct-developing frogs

   Pena-Jimenez, J.A. ; Burrowes, P.A. ( August 2021 , Herpetology notes)

   Kaiser, Hinrich ; Zagar, Anamarija ; Müller, Hendrik (Ed.)

   Abstract. Marking juveniles of terrestrial direct-developing frogs is challenging because of their small size (< 18 mm) and fragility. This difficulty has limited studies on demography or population dynamics where empirical data on the survivorship of juveniles or their recruitment to adulthood are missing. In a controlled laboratory experiment, we tested the survivorship of wild-caught juvenile Eleutherodactylus coqui Thomas, 1966 to marking with a single colour visual internal elastomer (VIE) in the thigh, with and without additional ventral skin-swabbing for disease or microbiome monitoring. Results revealed 100% survival in all groups, and all juveniles remained unharmed, moved freely, and fedmore »actively during three days after treatment, suggesting that this type of manipulation does not cause direct mortality. After 17 months of the experiment, we have recaptured 11% of the marked juveniles as adults, indicating that they can survive to recruitment age. We propose the use of a single VIE colour as a method to mark and follow date-specific cohorts of juvenile direct-developing frogs or young metamorphs until they reach older and larger age classes. This marking method can be used safely together with skin swabbing and provide valuable information for studies on population biology and age-specific response to environmental or disease stressors.« less
5. Quenching Factor consistency across several NaI(Tl) crystals

   https://doi.org/10.1088/1742-6596/2156/1/012065  

   Cintas, D. ; An, P. ; Awe, C. ; Barbeau, P. S. ; Barbosa de Souza, E. ; Hedges, S. ; Jo, J. H. ; Martínez, M. ; Maruyama, R. H. ; Li, L. ; et al ( December 2021 , Journal of Physics: Conference Series)

   Abstract Testing the DAMA/LIBRA annual modulation result independently of dark matter particle and halo models has been a challenge for twenty years. Using the same target material, NaI(Tl), is required and presently two experiments, ANAIS-112 and COSINE-100, are running for such a goal. A precise knowledge of the detector response to nuclear recoils is mandatory because this is the most likely channel to find the dark matter signal. The light produced by nuclear recoils is quenched with respect to that produced by electrons by a factor that has to be measured experimentally. However, current quenching factor measurements in NaI(Tl) crystalsmore »disagree within the energy region of interest for dark matter searches. To disentangle whether this discrepancy is due to intrinsic differences in the light response among different NaI(Tl) crystals, or has its origin in unaccounted for systematic effects will be key in the comparison among the different experiments. We present measurements of the quenching factors for five small NaI(Tl) crystals performed in the same experimental setup to control systematics. Quenching factor results are compatible between crystals and no clear dependence with energy is observed from 10 to 80 keVnr.« less