arXiv subjects

C. Capelli

Publications and source records attributed to C. Capelli.

At least 19 recordsLinked to original sources

arXiv2026

Constraints on Solar Reflected Dark Matter from a combined analysis of XENON1T and XENONnT data

We report on a search for sub-GeV dark matter upscattered via the solar reflection mechanism in the heavy mediator scenario. Under the Standard Halo Model, keV to MeV dark matter produces nuclear recoils with energies below the detection threshold of liquid xenon time projection chambers. We enhance sensitivity to low-mass dark matter by considering dark matter-electron scattering, employing dedicated event selections to reduce the detection threshold, and exploiting the additional kinetic energy imparted to the dark matter particle by solar upscattering. Using XENON1T ionization-only and XENONnT low-energy electronic recoil datasets, we exclude previously unconstrained DM-electron scattering cross section for masses between $4.6\, \text{keV/}c^2$ and $20\, \text{keV/}c^2$, and between $0.2\, \text{MeV/}c^2$ and $2\, \text{MeV/}c^2$, reaching a minimum of $3.41\times10^{-39}\, \text{cm}^2$ for a mass of $0.3\, \text{MeV/}c^2$ at 90\% confidence level.

hep-ex↗

arXiv2026

First Measurement of Solar Neutrinos through Elastic Neutrino-Electron Scattering at the keV Scale

We report on the first measurement of low-energy solar neutrinos through elastic neutrino-electron scattering in a dark matter experiment, establishing the lowest energy threshold for any neutrino detection to date. The measurement utilizes data from the first two science runs of XENONnT, corresponding to an exposure of 2.46 t $\cdot$ y, and covers electron recoil energies between 1 keV and 140 keV, providing sensitivity to solar neutrinos with energies down to 17 keV. We reject the background-only hypothesis with a statistical significance of $5.0σ$ and measure a solar $pp$ neutrino flux of $(10.2 \pm 2.0) \times 10^{10}$ cm$^{-2}$ s$^{-1}$. The result is larger, but statistically consistent with the previous measurement by Borexino at $1.9σ$. Together with recent observations of coherent elastic neutrino-nucleus scattering of $^8$B solar neutrinos in XENONnT and other liquid-xenon time projection chambers, these results demonstrate the growing potential of liquid xenon detectors for neutrino physics down to the keV-scale and represent an important milestone towards a next-generation multipurpose observatory.

hep-ex↗

arXiv2026

Probing the Solar $^8$B Neutrino Fog with XENONnT

We report a 3.3 $σ$ measurement of coherent elastic neutrino-nucleus scattering from solar $^8$B neutrinos using a 6.77 t$\times$yr exposure from the XENONnT experiment, inferring a solar $^8$B neutrino flux of $(5_{-2}^{+3})\times 10^6\,\mathrm{cm}^{-2}\mathrm{s}^{-1}$, consistent with previous measurements. In the presence of the $^8$B "neutrino fog", we find no evidence for light dark matter, and observe diminishing returns in sensitivity with increasing exposure. A 93% increase in exposure from the previous search improves the median sensitivity to the nucleon scattering cross section for a 5 GeV/$c^2$ spin-independent weakly interacting massive particle by 10%. The dataset was also used to measure the weak mixing angle at $\sim$ 0.02 GeV/$c$ momentum transfer and constrain physics beyond the Standard Model.

hep-ex↗

arXiv2026

Search for Magnetic and Spin-Independent Inelastic Dark Matter with XENONnT

We present a search for Magnetic and Spin-Independent inelastic Dark Matter using 2.1 tonne-years of data from the XENONnT experiment. We consider both single- and double-site event topologies, targeting the unique signature of an initial nuclear recoil followed by a delayed de-excitation photon. To suppress backgrounds, we introduce novel directional and kinematic selections based on the inferred speed and direction of the excited dark matter particle between the scatter and decay sites. We find that the collected data are consistent with background expectations, and report 90% C.L. upper limits for both models across the GeV/c2-TeV/c2 mass range.

hep-ex↗

arXiv2026

Light Dark Matter Search with 7.8 Tonne-Year of Ionization-Only Data in XENONnT

We report on a blinded search for dark matter (DM) using ionization-only (S2-only) signals in XENONnT with a total exposure of $7.83\mathrm{tonne}\times\mathrm{year}$ over 579 days in three science runs. Dedicated background suppression techniques and the first complete S2-only background model in XENONnT provide sensitivity to nuclear recoils of [0.5, 5.0] $\mathrm{keV_\mathrm{nr}}$ and electronic recoils of [0.04, 0.7] $\mathrm{keV_\mathrm{ee}}$. No significant excess over the expected background is observed, and we set 90\% confidence level upper limits on spin-independent DM--nucleon and spin-dependent DM--neutron scattering for DM masses between 3 and 8 $\mathrm{GeV}/c^2$, as well as on DM--electron scattering, axion-like particles, and dark photons, improving on previous constraints. For spin-independent DM--nucleon scattering, we exclude cross sections above $6.0\times10^{-45} $cm$^2$ at a DM mass of 5 $\mathrm{GeV}/c^2$, pushing the XENONnT sensitivity closer to the region where coherent elastic neutrino-nucleus scattering ($\text{CE}ν\text{NS}$) becomes an irreducible background.

hep-ex↗

arXiv2026

Direct Measurement of the $^{212}\mathrm{Pb}$ and $^{214}\mathrm{Pb}$ $β$ Decay Branching Ratios with the XENONnT Experiment

We present precision measurements of $^{212}\mathrm{Pb}$ and $^{214}\mathrm{Pb}$ $β$ decay branching ratios using $^{220}\mathrm{Rn}$ and $^{222}\mathrm{Rn}$ calibration data from the XENONnT detector, a dual-phase liquid xenon time projection chamber. Characterizing these isotopes is critical, as they lead to significant low-energy backgrounds in rare-event searches. We report ground-state branching ratios of $(14.75 \pm 0.20(\mathrm{stat}) ^{+0.14}_{-0.40}(\mathrm{sys}))\%$ for $^{212}\mathrm{Pb}$ and $(9.8 \pm 0.3(\mathrm{stat}) ^{+0.8}_{-0.2}(\mathrm{sys}))\%$ for $^{214}\mathrm{Pb}$, providing the most precise direct measurements of these transitions to date. These results contribute to enhancing background modeling for dark matter and neutrino experiments, improving sensitivity to solar neutrinos and physics beyond the Standard Model.

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arXiv2026

High-bandwidth frequency domain multiplexed readout of transition-edge sensors for neutrinoless double beta decay searches

The next-generation of cryogenic neutrinoless double-beta decay experiments require increasingly fast readout in order to improve background discrimination. These experiments, operated as cryogenic calorimeters at $\sim$10 mK, are usually read out by high-impedance neutron transmutation doped (NTD) thermistors, which provide good energy resolution, but are limited by $\sim$1 ms response times. Superconducting detectors, such as transition-edge sensors (TESs) with a time resolution of $\sim$100 $μ$s, offer superior timing performance over NTD semiconductor bolometers. To make this technology viable for an application to a thousand or more channels, multiplexed readout is necessary in order to minimize the thermal load and radioactive contamination induced by the readout. Frequency-domain multiplexing readout (fMUX) for TESs, previously developed at Berkeley Lab and McGill University, is currently in use for mm-wave telescopes with detector sampling rates in the order of 100 Hz. We demonstrate a new readout system, based on the McGill/Berkeley digital fMux readout, to satisfy the higher bandwidth and noise requirements of the next generation of TES-instrumented cryogenic calorimeters. Each multiplexing readout module comprises 10 superconducting resonators in the 1--5 MHz range and a DC superconducting quantum interference device (DC-SQUID), interfaced to high-speed field programmable gate array (FPGA)-based electronics for digital signal processing and low-latency SQUID feedback. The new readout samples detectors at 156 kHz, three orders of magnitude faster than its cosmology-oriented predecessor, and demonstrates a stable feedback bandwidth of 3 kHz in a real TES-based system.

physics.ins-det↗

arXiv2026

Model-independent searches of new physics in DARWIN with a semi-supervised deep learning pipeline

We present a novel deep learning pipeline to perform a model-independent, likelihood-free search for anomalous (i.e., non-background) events in the proposed next generation multi-ton scale liquid Xenon-based direct detection experiment, DARWIN. We train an anomaly detector comprising a variational autoencoder and a classifier on extensive, high-dimensional simulated detector response data and construct a one-dimensional anomaly score optimised to reject the background only hypothesis in the presence of an excess of non-background-like events. We benchmark the procedure with a sensitivity study that determines its power to reject the background-only hypothesis in the presence of an injected WIMP dark matter signal, outperforming the classical, likelihood-based background rejection test. We show that our neural networks learn relevant energy features of the events from low-level, high-dimensional detector outputs, without the need to compress this data into lower-dimensional observables, thus reducing computational effort and information loss. For the future, our approach lays the foundation for an efficient end-to-end pipeline that eliminates the need for many of the corrections and cuts that are traditionally part of the analysis chain, with the potential of achieving higher accuracy and significant reduction of analysis time.

physics.ins-det↗

arXiv2026

The detection of marine microseismic activity with the CUORE tonne-scale cryogenic experiment

Vibrations from experimental setups and the environment are a persistent source of noise for low-temperature calorimeters searching for rare events, including neutrinoless double beta ($0νββ$) decay or dark matter interactions. Such noise can significantly limit experimental sensitivity to the physics case under investigation. Here we report the first detection of marine microseismic vibrations using mK-scale calorimeters. This study employs a multi-device analysis correlating data from CUORE, the leading experiment in the search for $0νββ$ decay with mK-scale calorimeters and the Copernicus Earth Observation program, revealing the seasonal impact of Mediterranean Sea activity on CUORE's energy thresholds, resolution, and sensitivity over four years. The detection of marine microseisms underscores the need to address faint environmental noise in ultra-sensitive experiments. Understanding how such noise couples to the detector and developing mitigation strategies is essential for next-generation experiments. We demonstrate one such strategy: a noise decorrelation algorithm implemented in CUORE using auxiliary sensors, which reduces vibrational noise and improves detector performance. Enhancing sensitivity to $0νββ$ decay and to rare events with low-energy signatures requires identifying unresolved noise sources, advancing noise reduction methods, and improving vibration suppression systems, all of which inform the design of next-generation rare event experiments.

physics.ins-det↗

arXiv2026

Low-Energy Nuclear Recoil Calibration of XENONnT with a $^{88}$YBe Photoneutron Source

Characterizing low-energy, keV-range nuclear recoils near the detector threshold is one of the major challenges for large direct dark matter detectors. To that end, we have successfully used a Yttrium-Beryllium photoneutron source that emits 152 keV neutrons for the calibration of the light and charge yields of the XENONnT experiment for the first time. After data selection, we accumulated 474 events from 183 hours of exposure with this source. The expected background was $55 \pm 12$ accidental coincidence events, estimated using a dedicated 152 hour background calibration run with a Yttrium-PVC gamma-only source and data-driven modeling. From these calibrations, we extracted the light (charge) yield for liquid xenon at our field strength of 23 V/cm between 0.3 (0.7) keV$_{\rm NR}$ and 5.0 keV$_{\rm NR}$. This calibration is crucial for accurately measuring the solar $^8$B neutrino coherent elastic neutrino-nucleus scattering and searching for light dark matter particles with masses below 12 GeV/c$^2$.

physics.ins-det↗

arXiv2026

Challenging Spontaneous Quantum Collapse with XENONnT

We report on the search for X-ray radiation as predicted from dynamical quantum collapse with low-energy electronic recoil data in the energy range of 1-140 keV from the first science run of the XENONnT dark matter detector. Spontaneous radiation is an unavoidable effect of dynamical collapse models, which were introduced as a possible solution to the long-standing measurement problem in quantum mechanics. The analysis utilizes a model that for the first time accounts for cancellation effects in the emitted spectrum, which arise in the X-ray range due to the opposing electron-proton charges in xenon atoms. New world-leading limits on the free parameters of the Markovian continuous spontaneous localization and Diósi-Penrose models are set, improving previous best constraints by two orders of magnitude and a factor of five, respectively. The original values proposed for the strength and the correlation length of the continuous spontaneous localization model are excluded experimentally for the first time.

hep-ex↗

arXiv2026

Enhancing Neutrinoless Double-Beta Decay Sensitivity of Liquid-Xenon Time Projection Chamber with Augmented Convolutional Neural Network

Dual-phase time projection chamber (TPC) that employs a multi-ton-scale liquid xenon (LXe) target mass is a pioneering detector technology to search for dark matter. Beyond its advantage in dark matter direct detection efforts, the natural xenon target allows it to search for the neutrinoless double-beta decay ($0νββ$) process, which would violate lepton number conservation and indicate that neutrinos are Majorana particles. However, such $0νββ$ searches have been limited by gamma-ray backgrounds originating from the detector materials. In this work, we designed an augmented convolutional neural network (A-CNN) model to extract additional event-topology information from detector data. Using simulation and calibration data from XENONnT, a leading LXe TPC experiment, our model achieved over 60% background rejection while maintaining 90% signal acceptance. This rejection power improves XENONnT's projected sensitivity of the $^{136}$Xe $0νββ$ search by about 40%. The implementation of A-CNN in the data analysis of future liquid xenon observatories, such as XLZD, will further enhance their sensitivities for $0νββ$ with $^{136}$Xe.

physics.ins-det↗

arXiv2026

Exploring the keV-scale physics potential of CUORE

We present the analysis techniques developed to explore the keV-scale energy region of the CUORE experiment, based on more than 2 tonne yr of data collected over 5 years. By prioritizing a stricter selection over a larger exposure, we are able to optimize data selection for thresholds at 10 keV and 3 keV with 691 kg yr and 11 kg yr of data, respectively. We study how the performance varies among the 988-detector array with different detector characteristics and data taking conditions. We achieve an average baseline resolution of 2.54 $\pm$ 0.14 keV FWHM and 1.18 $\pm$ 0.02 keV FWHM for the data selection at 10 keV and 3 keV, respectively. The analysis methods employed reduce the overall background by about an order of magnitude, reaching 2.06 $\pm$ 0.05 counts/(keV kg days) and 16 $\pm$ 2 counts/(keV kg days) at the thresholds of 10 keV and 3 keV. We evaluate for the first time the near-threshold reconstruction efficiencies of the CUORE experiment, and find these to be 26 $\pm$ 4 \% and 50 $\pm$ 2 \% at 3 keV and 10 keV, respectively. This analysis provides crucial insights into rare decay studies, new physics searches, and keV-scale background modeling with CUORE. We demonstrate that tonne-scale cryogenic calorimeters can operate across a wide energy range, from keV to MeV, establishing their scalability as versatile detectors for rare event and dark matter physics. These findings also inform the optimization of future large mass cryogenic calorimeters to enhance the sensitivity to low-energy phenomena.

hep-ex↗

arXiv2026

Sensitivity of the CUPID experiment to $0νββ$ decay of $^{100}$Mo

CUPID is a next-generation bolometric experiment to search for neutrinoless double-beta decay ($0νββ$) of $^{100}$Mo using Li$_2$MoO$_4$ scintillating crystals. It will operate 1596 crystals at $\sim$10 mK in the CUORE cryostat at the Laboratori Nazionali del Gran Sasso in Italy. Each crystal will be facing two Ge-based bolometric light detectors for $α$ rejection. We compute the discovery and the exclusion sensitivity of CUPID to $0νββ$ in a Frequentist and a Bayesian framework. This computation is done numerically based on pseudo-experiments. For the CUPID baseline scenario, with a background and an energy resolution of $1.0 \times 10^{-4}$ counts/keV/kg/yr and 5 keV FWHM at the Q-value, respectively, this results in a Bayesian exclusion sensitivity (90% c.i.) of $\hat{T}_{1/2} > 1.6 \times 10^{27} \ \mathrm{yr}$, corresponding to the effective Majorana neutrino mass of $\hat{m}_{ββ} < \ 9.6$ -- $28 \ \mathrm{meV}$. The Frequentist discovery sensitivity (3$σ$) is $\hat{T}_{1/2}= 1.0 \times 10^{27} \ \mathrm{yr}$, corresponding to $\hat{m}_{ββ}= \ 12$ -- $36 \ \mathrm{meV}$.

nucl-ex↗

arXiv2025

WIMP Dark Matter Search using a 3.1 Tonne-Year Exposure of the XENONnT Experiment

We report on a search for weakly interacting massive particle (WIMP) dark matter (DM) via elastic DM-xenon-nucleus interactions in the XENONnT experiment. We combine datasets from the first and second science campaigns resulting in a total exposure of 3.1 tonne-years. In a blind analysis of nuclear recoil events with energies above $3.8\,\mathrm{keV_{NR}}$, we find no significant excess above background. We set new upper limits on the spin-independent WIMP-nucleon scattering cross section for WIMP masses above $10\,\mathrm{GeV}/c^2$ with a minimum of $1.7\,\times\,10^{-47}\,\mathrm{cm^2}$ at $90\,\%$ confidence level for a WIMP mass of $30\,\mathrm{GeV}/c^2$. We achieve a best median sensitivity of $1.4\,\times\,10^{-47}\,\mathrm{cm^2}$ for a $41\,\mathrm{GeV}/c^2$ WIMP. Compared to the result from the first XENONnT science dataset, we improve our sensitivity by a factor of up to 1.8.

hep-ex↗

arXiv2025

End-to-End Data Analysis Methods for the CUORE Experiment

The Cryogenic Underground Observatory for Rare Events (CUORE) experiment set the most stringent limit on the neutrinoless double-beta ($0νββ$) decay half-life of $^{130}$Te with 2 ton yr TeO$_2$ analyzed exposure. In addition to $0νββ$ decay, the CUORE detector -- a ton-scale array of nearly 1000 cryogenic calorimeters operating at $\sim$10 mK -- is capable of searching for other rare decays and interactions over a broad energy range. For our searches, we leverage the available information of each calorimeter by performing its optimization, data acquisition, and analysis independently. We describe the analysis tools and methods developed for CUORE and their application to build high-quality datasets for numerous physics searches. In particular, we describe in detail our evaluation of the energy-dependent detector response and signal efficiency used in the most recent search for $0νββ$ decay.

nucl-ex↗

arXiv2025

The XLZD Design Book: Towards the Next-Generation Liquid Xenon Observatory for Dark Matter and Neutrino Physics

This report describes the experimental strategy and technologies for XLZD, the next-generation xenon observatory sensitive to dark matter and neutrino physics. In the baseline design, the detector will have an active liquid xenon target of 60 tonnes, which could be increased to 80 tonnes if the market conditions for xenon are favorable. It is based on the mature liquid xenon time projection chamber technology used in current-generation experiments, LZ and XENONnT. The report discusses the baseline design and opportunities for further optimization of the individual detector components. The experiment envisaged here has the capability to explore parameter space for Weakly Interacting Massive Particle (WIMP) dark matter down to the neutrino fog, with a 3$σ$ evidence potential for WIMP-nucleon cross sections as low as $3\times10^{-49}\rm\,cm^2$ (at 40 GeV/c$^2$ WIMP mass). The observatory will also have leading sensitivity to a wide range of alternative dark matter models. It is projected to have a 3$σ$ observation potential of neutrinoless double beta decay of $^{136}$Xe at a half-life of up to $5.7\times 10^{27}$ years. Additionally, it is sensitive to astrophysical neutrinos from the sun and galactic supernovae.

hep-ex↗

arXiv2025

Constraints on Lepton Number Violation with the 2 tonne$\cdot$yr CUORE Dataset

Matter-antimatter asymmetry underlines the incompleteness of the current understanding of particle physics. Neutrinoless double-beta decay ($0νββ$) may help explain this asymmetry, while unveiling the Majorana nature of the neutrino. The CUORE experiment searches for $0νββ$ of $^{130}$Te using a tonne-scale cryogenic calorimeter operated at milli-kelvin temperatures. We report no evidence of $0νββ$ and place a lower limit on the half-life of $T_{1/2} >3.5 \times$ 10$^{25}$~years (90\% C.I.) with over 2~tonne$\cdot$year TeO$_2$ exposure. The tools and techniques developed for this result and the 5 year stable operation of nearly 1000 detectors demonstrate crucial infrastructure for a future-generation experiment capable of searching for $0νββ$ across multiple isotopes.

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