arXiv subjects

D. F. F. S. Cavalcante

Publications and source records attributed to D. F. F. S. Cavalcante.

16 recordsLinked to original sources

arXiv2026

Achieving a 0.49 keV threshold in the COSINE-100 dark matter experiment

The COSINE-100 experiment searched for weakly interacting massive particles (WIMPs) with NaI(Tl) crystals at the Yangyang Underground Laboratory. Using its full 6-year dataset, we lower the analysis threshold to 0.49 keV. A multi-layer perceptron classifier separates scintillation events from photomultiplier tube noise. It is trained with approximately $3\times10^{6}$ simulated scintillation waveforms per crystal, separately for groups of events with similar numbers of photoelectron clusters. The selection keeps more than 10% of scintillation events at 0.49 keV while limiting noise contamination to below 1%. The selection efficiency is validated with $^{22}$Na-calibration data and internal $^{22}$Na events, and the selection performance is stable over the six years of data taking. With this threshold, the median expected upper limit on the spin-dependent WIMP-proton cross section reaches $1.1\times10^{-36}$ cm$^2$ at a WIMP mass of 2.5 GeV/$c^2$, probing previously unexplored parameter space in the 2.0-2.8 GeV/$c^2$ mass range.

hep-ex↗

arXiv2026

Cryogenic characterisation of the FBK NUV-HD-cryo Silicon Photomultipliers for the DarkSide-20k dark matter experiment

Liquid Argon Time Projection Chambers (TPCs) are highly promising detectors for dark matter searches due to their uniform response, scalability to large target masses, and compatibility with ultra-low background conditions. The DarkSide-20k (DS-20k) experiment, currently under construction at Istituto Nazionale di Fisica Nucleare (INFN) Laboratori Nazionali del Gran Sasso (LNGS), aims to achieve unprecedented sensitivity to Weakly Interacting Massive Particles (WIMPs), approaching the neutrino fog. At the heart of the detector is a dual-phase TPC filled and surrounded by low-radioactivity argon from underground sources (i.e. Underground Argon (UAr)), functioning both as the WIMP target and detection medium. The experiment employs Fondazione Bruno Kessler (FBK) NUV-HD-cryo Silicon Photomultipliers (SiPMs) as the chosen photon sensors for its optical planes. Key SiPM properties such as dark noise rate, gain and direct crosstalk were measured using specialized test setups at 77 K. The photon detection efficiency (PDE) was measured under vacuum at 77 K over the wavelength range 350-820 nm. Secondary photon emission, which can give rise to external optical crosstalk, was measured under vacuum at 86 K over the wavelength range 550-1020 nm.

physics.ins-det↗

arXiv2026

Probing unexplored spin-dependent dark matter-proton coupling with few-photoelectron threshold in COSINE-100

We report new constraints on the spin-dependent scattering cross section between low-mass dark matter and protons using data collected by the COSINE-100 experiment. By implementing a specialized event selection process using a multi-layer perceptron and robust noise mitigation, this analysis pioneers a detection threshold of 3 and 4 isolated peaks, corresponding to the reconstructed photoelectrons, which are significantly lower than the 8 photoelectron threshold used in previous analyses. In this unstudied few-photoelectron regime, where instrumental noise and phosphorescence are prevalent, we utilize a phenomenological background model to search for the annual modulation signal expected from the Standard Halo Model. No statistically significant annual modulation is observed in our data. We derive new 90% confidence level (C.L.) upper limits for the spin-dependent DM-proton cross section, establishing the world's most stringent constraints in the 1.75-2.25 GeV/c$^2$ mass range. Furthermore, by incorporating the Migdal effect, we extend the experimental sensitivity to the sub-GeV/c$^2$ regime, setting world-leading limits in the 15-58 MeV/c$^2$ range. These results demonstrate the capability of NaI(Tl) target materials to probe previously unexplored regions of the dark matter parameter space.

hep-ex↗

arXiv2026

Constraints on sub-GeV dark matter scattering on electrons with COSINE-100

We present results of the search for sub-GeV dark matter interaction with electrons in the NaI(Tl) crystals of the COSINE-100 experiment. The two benchmark scenarios of a heavy and a light vector boson as mediator of the interaction were studied. We found no excess events over the expected background in a data-set of 2.82 years, with a total exposure of 172.9 kg-year. The derived 90% confidence level upper limits exclude a DM-electron scattering cross section above 6.4 $\times$ 10$^{-33}$ cm$^2$ for a DM mass of 0.25 GeV, assuming a light mediator; and above 3.4 $\times$ 10$^{-37}$ cm$^2$ for a 0.4 GeV DM, assuming a heavy mediator, and represent the most stringent constraints for a NaI(Tl) target to date. We also briefly discuss a planned analysis using an annual modulation method below the current 0.7 keV threshold of COSINE-100, down to few photoelectrons yield.

hep-ex↗

arXiv2025

Limits on WIMP dark matter with NaI(Tl) crystals in three years of COSINE-100 data

We report limits on WIMP dark matter derived from three years of data collected by the COSINE-100 experiment with NaI(Tl) crystals, achieving an improved energy threshold of 0.7 keV. This lowered threshold enhances sensitivity in the sub-GeV mass range, extending the reach for direct detection of low-mass dark matter. Although no excess of WIMP-like events was observed, the increased sensitivity enabled a model-insensitive comparison between the expected WIMP signal rate-based on mass limits from our data-and DAMA's reported modulation amplitude. Our findings strongly disfavor the DAMA signal as originating from WIMP interactions, fully excluding DAMA/LIBRA 3$σ$ allowed regions and providing enhanced WIMP mass limits by an order of magnitude in the spin-independent model compared to previous results. In the spin-dependent model, cross-section upper limits were obtained in the mass range [0.1-5.0] GeV/c$^2$, with additional sensitivity to sub-GeV WIMPs through the inclusion of the Migdal effect. These results represent substantial progress in low-mass dark matter exploration and reinforce constraints on the longstanding DAMA claim.

hep-ex↗

arXiv2025

Combined Annual Modulation Dark Matter Search with COSINE-100 and ANAIS-112

The annual modulation signal, claimed to be consistent with dark matter as observed by DAMA/LIBRA in a sodium-iodide based detector, has persisted for over two decades. COSINE-100 and ANAIS-112 were designed to test the claim directly using the same target material. COSINE-100, located at Yangyang Underground Laboratory in South Korea, and ANAIS-112, located at Canfranc Underground Laboratory in Spain, have been taking data since 2016 and 2017, respectively. Each experiment published its respective results independently. In this paper, we present the results of an annual modulation search as a test of the signal observed by DAMA/LIBRA with the first three respective years of data from COSINE-100 and ANAIS-112. Using a Markov Chain Monte Carlo method, we find best fit values for modulation amplitude of $-0.0002 {\pm} 0.0026$ cpd/kg/keV in the 1-6 keV and $0.0021 {\pm} 0.0028$ cpd/kg/keV in the 2-6 keV energy regions. These results are not compatible with DAMA/LIBRA's assertion for their observation of annual modulation at $3.7σ$ and $2.6σ$, respectively. Performing a simple combination of the newly released 6-years datasets from both experiments find values consistent with no modulation at $0.0005 {\pm} 0.0019$ cpd/kg/keV in the 1-6 keV and $0.0027 {\pm} 0.0021$ cpd/kg/keV in the 2-6 keV energy regions with $4.68σ$ and $3.53σ$ respective exclusions of the DAMA/LIBRA signal.

astro-ph.IM↗

arXiv2025

COSINE-100 Full Dataset Challenges the Annual Modulation Signal of DAMA/LIBRA

For over 25 years, the DAMA/LIBRA collaboration has claimed to observe an annual modulation signal, suggesting the existence of dark matter interactions. However, no experiment employing different target materials has observed a dark matter signal consistent with their result. To address this puzzle, the COSINE-100 collaboration conducted a model-independent test using sodium iodide crystal detectors, the same target material as DAMA/LIBRA. Analyzing data collected over 6.4 years by the effective mass of 61.3 kg, with improved energy calibration and time-dependent background modeling, we found no evidence of an annual modulation signal, challenging the DAMA/LIBRA result with a confidence level greater than 3$σ$. This finding represents a substantial step toward resolving the long-standing debate surrounding DAMA/LIBRA's dark matter claim, indicating that the observed modulation is unlikely to be caused by dark matter interactions.

hep-ex↗

arXiv2024

Lowering threshold of NaI(Tl) scintillator to 0.7 keV in the COSINE-100 experiment

COSINE-100 is a direct dark matter search experiment, with the primary goal of testing the annual modulation signal observed by DAMA/LIBRA, using the same target material, NaI(Tl). In previous analyses, we achieved the same 1 keV energy threshold used in the DAMA/LIBRA's analysis that reported an annual modulation signal with 11.6$σ$ significance. In this article, we report an improved analysis that lowered the threshold to 0.7 keV, thanks to the application of Multi-Layer Perception network and a new likelihood parameter with waveforms in the frequency domain. The lower threshold would enable a better comparison of COSINE-100 with new DAMA results with a 0.75 keV threshold and account for differences in quenching factors. Furthermore the lower threshold can enhance COSINE-100's sensitivity to sub-GeV dark matter searches.

hep-ex↗

arXiv2024

Improved background modeling for dark matter search with COSINE-100

COSINE-100 aims to conclusively test the claimed dark matter annual modulation signal detected by DAMA/LIBRA collaboration. DAMA/LIBRA has released updated analysis results by lowering the energy threshold to 0.75 keV through various upgrades. They have consistently claimed to have observed the annual modulation. In COSINE-100, it is crucial to lower the energy threshold for a direct comparison with DAMA/LIBRA, which also enhances the sensitivity of the search for low-mass dark matter, enabling COSINE-100 to explore this area. Therefore, it is essential to have a precise and quantitative understanding of the background spectrum across all energy ranges. This study expands the background modeling from 0.7 to 4000 keV using 2.82 years of COSINE-100 data. The modeling has been improved to describe the background spectrum across all energy ranges accurately. Assessments of the background spectrum are presented, considering the nonproportionality of NaI(Tl) crystals at both low and high energies and the characteristic X-rays produced by the interaction of external backgrounds with materials such as copper. Additionally, constraints on the fit parameters obtained from the alpha spectrum modeling fit are integrated into this model. These improvements are detailed in the paper.

astro-ph.IM↗

arXiv2024

Real-time portable muography with Hankuk Atmospheric-muon Wide Landscaping : HAWL

Cosmic ray muons prove valuable across various fields, from particle physics experiments to non-invasive tomography, thanks to their high flux and exceptional penetrating capability. Utilizing a scintillator detector, one can effectively study the topography of mountains situated above tunnels and underground spaces. The Hankuk Atmospheric-muon Wide Landscaping (HAWL) project successfully charts the mountainous region of eastern Korea by measuring cosmic ray muons with a detector in motion. The real-time muon flux measurement shows a tunnel length accuracy of 6.0 %, with a detectable overburden range spanning from 8 to 400 meter-water-equivalent depth. This is the first real-time portable muon tomography.

hep-ex↗

arXiv2024

Nonproportionality of NaI(Tl) Scintillation Detector for Dark Matter Search Experiments

We present a comprehensive study of the nonproportionality of NaI(Tl) scintillation detectors within the context of dark matter search experiments. Our investigation, which integrates COSINE-100 data with supplementary $γ$ spectroscopy, measures light yields across diverse energy levels from full-energy $γ$ peaks produced by the decays of various isotopes. These $γ$ peaks of interest were produced by decays supported by both long and short-lived isotopes. Analyzing peaks from decays supported only by short-lived isotopes presented a unique challenge due to their limited statistics and overlapping energies, which was overcome by long-term data collection and a time-dependent analysis. A key achievement is the direct measurement of the 0.87 keV light yield, resulting from the cascade following electron capture decay of $^{22}$Na from internal contamination. This measurement, previously accessible only indirectly, deepens our understanding of NaI(Tl) scintillator behavior in the region of interest for dark matter searches. This study holds substantial implications for background modeling and the interpretation of dark matter signals in NaI(Tl) experiments.

hep-ex↗

arXiv2024

Alpha backgrounds in NaI(Tl) crystals of COSINE-100

COSINE-100 is a dark matter direct detection experiment with 106 kg NaI(Tl) as the target material. 210Pb and daughter isotopes are a dominant background in the WIMP region of interest and are detected via beta decay and alpha decay. Analysis of the alpha channel complements the background model as observed in the beta/gamma channel. We present the measurement of the quenching factors and Monte Carlo simulation results and activity quantification of the alpha decay components of the COSINE-100 NaI(Tl) crystals. The data strongly indicate that the alpha decays probabilistically undergo two possible quenching factors but require further investigation. The fitted results are consistent with independent measurements and improve the overall understanding of the COSINE-100 backgrounds. Furthermore, the half-life of 216Po has been measured to be 143.4 +/- 1.2 ms, which is consistent with and more precise than recent measurements.

astro-ph.IM↗

arXiv2023

Search for inelastic WIMP-iodine scattering with COSINE-100

We report the results of a search for inelastic scattering of weakly interacting massive particles (WIMPs) off $^{127}$I nuclei using NaI(Tl) crystals with a data exposure of 97.7 kg$\cdot$years from the COSINE-100 experiment. The signature of inelastic WIMP-$^{127}$I scattering is a nuclear recoil accompanied by a 57.6 keV $γ$-ray from the prompt deexcitation, producing a more energetic signal compared to the typical WIMP nuclear recoil signal. We found no evidence for this inelastic scattering signature and set a 90 $\%$ confidence level upper limit on the WIMP-proton spin-dependent, inelastic scattering cross section of $1.2 \times 10^{-37} {\rm cm^{2}}$ at the WIMP mass 500 ${\rm GeV/c^{2}}$.

hep-ex↗

arXiv2023

Search for Boosted Dark Matter in COSINE-100

We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7 kg$\cdot$years exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4\,MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.

hep-ex↗

arXiv2023

Search for bosonic super-weakly interacting massive particles at COSINE-100

We present results of a search for bosonic super-weakly interacting massive particles (BSW) as keV scale dark matter candidates that is based on an exposure of 97.7 kg$\cdot$year from the COSINE experiment. In this search, we employ, for the first time, Compton-like as well as absorption processes for pseudoscalar and vector BSWs. No evidence for BSWs is found in the mass range from 10 $\mathrm{keV/c}^2$ to 1 $\mathrm{MeV/c}^2$, and we present the exclusion limits on the dimensionless coupling constants to electrons $g_{ae}$ for pseudoscalar and $κ$ for vector BSWs at 90% confidence level. Our results show that these limits are improved by including the Compton-like process in masses of BSW, above $\mathcal{O}(100\,\mathrm{keV/c}^2)$.

hep-ex↗

arXiv2023

Search for solar bosonic dark matter annual modulation with COSINE-100

We present results from a search for solar bosonic dark matter using the annual modulation method with the COSINE-100 experiment. The results were interpreted considering three dark sector bosons models: solar dark photon; DFSZ and KSVZ solar axion; and Kaluza-Klein solar axion. No modulation signal that is compatible with the expected from the models was found from a data-set of 2.82 yr, using 61.3 kg of NaI(Tl) crystals. Therefore, we set a 90$\%$ confidence level upper limits for each of the three models studied. For the solar dark photon model, the most stringent mixing parameter upper limit is $1.61 \times 10^{-14}$ for dark photons with a mass of 215 eV. For the DFSZ and KSVZ solar axion, and the Kaluza-Klein axion models, the upper limits exclude axion-electron couplings, $g_{ae}$, above $1.61 \times 10^{-11}$ for axion mass below 0.2 keV; and axion-photon couplings, $g_{aγγ}$, above $1.83 \times 10^{-11}$ GeV$^{-1}$ for an axion number density of $4.07 \times 10^{13}$ cm$^{-3}$. This is the first experimental search for solar dark photons and DFSZ and KSVZ solar axions using the annual modulation method. The lower background, higher light yield and reduced threshold of NaI(Tl) crystals of the future COSINE-200 experiment are expected to enhance the sensitivity of the analysis shown in this paper. We show the sensitivities for the three models studied, considering the same search method with COSINE-200.

hep-ex↗