arXiv subjects

K. M. Heeger

Publications and source records attributed to K. M. Heeger.

At least 19 recordsLinked to original sources

arXiv2026

Gamma Backgrounds for Experiments at the High Flux Isotope Reactor

This article describes the deployment of a germanium detector at Oak Ridge National Lab's High Flux Isotope Reactor (HFIR) for the purpose of understanding the energy and spatial distribution of the gamma field in the experiment hall where the Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) took data and future neutrino experiments could be located. The sources from both the reactor and the neutron beamlines are described in detail, along with their temporal variations due to reactor power and their spatial variations due to the geometry of the beamlines and building materials in the vicinity. Additionally, a shielding study was performed to assess the amount that backgrounds in tens of keV range can be mitigated. This work helps inform backgrounds for future experiments at reactors such as IBD-based neutrino measurements and CEvNS measurements.

hep-ex↗

arXiv2026

Probing Long-Lived Particle Production in Muon Decays at the SNS with a Highly Capable Hydrocarbon Detector

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) is a prolific muon producer, making it an ideal location for studying dark sector particles produced in muon decays at rest. In this paper, we explore sub-GeV dark particle detection possibilities in a tons-scale, highly capable hydrocarbon scintillator ($HC^2$) detector at the SNS. We consider a search for $e^+e^-$ final states produced by decays of long-lived, $O(10-100)$ MeV axion-like particles and heavy neutral leptons. The $HC^2$ technology space, exemplified by the PROSPECT and Mobile Antineutrino Demonstrator detectors, offers strong rejection capabilities for the cosmic ray backgrounds that would normally dominate this search. By benchmarking on-surface cosmic ray signatures with data from PROSPECT at ORNL, we generate robust predictions for a multi-year SNS deployment of a range of $HC^2$ detector implementations. Results indicate the potential for order-of-magnitude improvements in sensitivity to axion-like particles and heavy neutral leptons in the 10-100 MeV mass regime compared to current global limits. We also comment on the neutrino detection possibilities of a $HC^2$ deployment at the SNS.

hep-ex↗

arXiv2026

New Deep Learning Data Analysis Method for PROSPECT using GAPE: Genetic Algorithm Powered Evolution

We propose a genetic algorithm powered evolution (GAPE) method to create deep learning solutions for energy and position estimation for reactor antineutrino interactions in the Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) at the highly enriched High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. We also apply GAPE to create classification models to distinguish signatures of inverse beta decay (IBD) interactions of reactor antineutrinos from common background types. The GAPE method can also be adopted for optimization of other types of problems that utilize machine learning (ML) models for particle physics applications. When applied in the PROSPECT context, we find that the models selected by GAPE can, in some cases, outperform the traditional models previously used for PROSPECT data analysis. In particular, when benchmarked against conventional PROSPECT neutrino identification pathways using the same underlying information, the classifier offers the promise of improving the signal-to-background ratio by nearly 2.8 times. Performance biases uncovered during initial IBD classifier validation were primarily caused by differences in time-dependent response between background and signal training datasets. Biases were effectively mitigated through a data-period-specific training regimen, offering a pathway towards realizing an unbiased IBD signal classifier for future reactor neutrino datasets.

physics.data-an↗

arXiv2026

Cyclotron Radiation Signal Characterization in Resonant Cavities for the Project 8 Neutrino Mass Experiment

Many experimental methods in physics require understanding radiation from single particles into non-trivial electromagnetic mode structures. Such characterization is critical for Cyclotron Radiation Emission Spectroscopy (CRES), an advancing new measurement technique that has the potential to greatly benefit fundamental physics measurements. In CRES, charged particles emit cyclotron radiation at frequencies that provide their energy measurement. As a notable example, the Project 8 experiment aims to kinematically infer the neutrino mass by measuring the energies of electrons emitted in tritium beta decay using CRES. In near-term realizations of Project 8, resonant cylindrical cavities will be used for CRES readout, in a configuration with a magnetic field oriented along the symmetry axis, and electrons following helical cyclotron trajectories confined to the cavity interior. The physics of electromagnetic radiation in these environments is complicated, since it involves both the motion of the emitting particle and the mode structure imposed by the cavity. In this work, we derive and validate an analytic model for how an oscillating, trapped electron radiates into cavity modes, and the power and frequency content of the radiation that can be read out from these events. These results can be used to guide the design of cavities for future CRES and other experiments.

physics.ins-det↗

arXiv2025

A prototype reactor-antineutrino detector based on $^6$Li-doped pulse-shaping-discriminating plastic scintillator

An aboveground 60-kg reactor-antineutrino detector prototype, comprised of a 2-dimensional array of 36 $^{6}$Li-doped pulse shape sensitive plastic scintillator bars, is described. Each bar is 50~cm long with a square cross section of 5.5~cm. Doped with $^{6}$Li at 0.1\% by mass, the detector is capable of identifying correlated energy depositions for the detection of reactor antineutrinos via the inverse-beta-decay reaction. Each bar is wrapped with a specular reflector that directs photons towards PMTs mounted at both ends of the bar. This paper highlights the construction, key features, and main performance characteristics of the system. The system, which relies on multiple observables such as PSD, energy, position, and timing, is capable of detecting IBD-like neutron-correlated backgrounds, long-lived decay chains, and cosmogenic isotopes.

physics.ins-det↗

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

Final Search for Short-Baseline Neutrino Oscillations with the PROSPECT-I Detector at HFIR

The PROSPECT experiment is designed to perform precise searches for antineutrino disappearance at short distances (7 - 9~m) from compact nuclear reactor cores. This Letter reports results from a new neutrino oscillation analysis performed using the complete data sample from the PROSPECT-I detector operated at the High Flux Isotope Reactor in 2018. The analysis uses a multi-period selection of inverse beta decay neutrino interactions with reduced backgrounds and enhanced statistical power to set limits on electron-flavor disappearance caused by mixing with sterile neutrinos with 0.2 - 20 eV$^2$ mass splittings. Inverse beta decay positron energy spectra from six different reactor-detector distance ranges are found to be statistically consistent with one another, as would be expected in the absence of sterile neutrino oscillations. The data excludes at 95% confidence level the existence of sterile neutrinos in regions above 3~eV$^2$ previously unexplored by terrestrial experiments, including all space below 10~eV$^2$ suggested by the recently strengthened Gallium Anomaly. The best-fit point of the Neutrino-4 reactor experiment's claimed observation of short-baseline oscillation is ruled out at more than five standard deviations.

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.

nucl-ex↗

arXiv2025

Reconstruction of cosmic-ray muon events with CUORE

We report the in-situ 3D reconstruction of through-going muons in the CUORE experiment, a cryogenic calorimeter array searching for neutrinoless double beta ($0\nu\beta\beta$) decay, leveraging the segmentation of the detector. Due to the slow time response of the detector, time-of-flight estimation is not feasible. Therefore, the track reconstruction is performed using a multi-objective optimization algorithm that relies on geometrical information from the detector as a whole. We measure the integral flux of cosmic-ray muons underground at the {\it Laboratori Nazionali del Gran Sasso}, and find our value to be in good agreement with other experiments that have performed a similar measurement. To our knowledge, this work represents the first demonstration of 3D particle tracking and reconstruction of through-going muons with per-event angular determination in a millikelvin cryogenic detector array. The analysis performed for this work will be critical for validating the muon-related background in CUPID, a next-generation $0\nu\beta\beta$ experiment, and for follow-up studies on detector response and on delayed products induced by cosmic-ray muons.

physics.ins-det↗

arXiv2025

Dynamics of Magnetic Evaporative Beamline Cooling for Preparation of Cold Atomic Beams

The most sensitive direct neutrino mass searches today are based on measurement of the endpoint of the beta spectrum of tritium to infer limits on the mass of the unobserved neutrino. To avoid the smearing associated with the distribution of molecular final states in the T-He molecule, the next generation of these experiments will need to employ atomic (T) rather than molecular (T$_{2}$) tritium sources, at currents of at least 10$^{15}$ atoms per second. Following production, atomic T can be trapped in gravitational and/or magnetic bottles for beta spectrum experiments, if and only if it can first be cooled to millikelvin temperatures. Accomplishing this cooling presents substantial technological challenges. The Project 8 collaboration is developing a technique based on magnetic evaporative cooling along a beamline (MECB) for the purpose of cooling T to feed a magneto-gravitational trap that also serves as a cyclotron radiation emission spectroscope. Initial tests of the approach are planned in a pathfinder apparatus using atomic Li. This paper presents a method for analyzing the dynamics of the MECB technique, and applies these calculations to the design of systems for cooling and slowing of atomic Li and T. A scheme is outlined that could provide a current of T at the millikelvin temperatures required for the Project 8 neutrino mass search.

physics.ins-det↗

arXiv2025

CUPID, the CUORE Upgrade with Particle IDentification

CUPID, the CUORE Upgrade with Particle IDentification, is a next-generation experiment to search for neutrinoless double beta decay ($0νββ$) and other rare events using enriched Li$_2$$^{100}$MoO$_4$ scintillating bolometers. It will be hosted by the CUORE cryostat located at the Laboratori Nazionali del Gran Sasso in Italy. The main physics goal of CUPID is to search for $0νββ$\ of $^{100}$Mo with a discovery sensitivity covering the full neutrino mass regime in the inverted ordering scenario, as well as the portion of the normal ordering regime with lightest neutrino mass larger than 10 meV. With a conservative background index of 10$^{-4}$ cnts/(keV$\cdot$kg$\cdot$yr), 240 kg isotope mass, 5 keV FWHM energy resolution at 3 MeV and 10 live-years of data taking, CUPID will have a 90\% C.L. half-life exclusion sensitivity of 1.8 $\cdot$ 10$^{27}$ yr, corresponding to an effective Majorana neutrino mass ($m_{ββ}$) sensitivity of 9--15 meV, and a $3σ$ discovery sensitivity of 1 $\cdot$ 10$^{27}$ yr, corresponding to an $m_{ββ}$ range of 12--21 meV.

physics.ins-det↗

arXiv2025

Machine Learning for Single-Ended Event Reconstruction in PROSPECT Experiment

The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, was a segmented antineutrino detector that successfully operated at the High Flux Isotope Reactor in Oak Ridge, TN, during its 2018 run. Despite challenges with photomultiplier tube base failures affecting some segments, innovative machine learning approaches were employed to perform position and energy reconstruction, and particle classification. This work highlights the effectiveness of convolutional neural networks and graph convolutional networks in enhancing data analysis. By leveraging these techniques, a 3.3\% increase in effective statistics was achieved compared to traditional methods, showcasing their potential to improve analysis performance. Furthermore, these machine learning methodologies offer promising applications for other segmented particle detectors, underscoring their versatility and impact.

physics.data-an↗

arXiv2025

The real-time data processing and acquisition system for Project 8 Phase II

In Phase II of the Project 8 neutrino mass experiment, electrons from the decays of tritium or ${}^{83\mathrm{m}}$Kr are detected via their $\approx$26 GHz cyclotron radiation while contained within a circular waveguide. The signal from a given electron is characterized as a brief chirp, lasting $\lesssim$10 ms and changing in frequency by $\lesssim$1 MHz/ms. To detect these signals, the Project 8 collaboration developed a data acquisition (DAQ) system tailored to the signal properties. The DAQ is responsible for simultaneously selecting up to three 100 MHz-wide frequency windows to study, detect, and trigger on likely signals from different electron kinetic energies, and for writing the relevant data to disk. We describe the Phase II DAQ system in detail and address how the system was used for data-taking operations.

physics.ins-det↗

arXiv2025

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↗

arXiv2025

Comprehensive Measurement of the Reactor Antineutrino Spectrum and Flux at Daya Bay

This Letter reports the precise measurement of reactor antineutrino spectrum and flux based on the full data set of 4.7 million inverse-beta-decay (IBD) candidates collected at Daya Bay near detectors. Expressed in terms of the IBD yield per fission, the antineutrino spectra from all reactor fissile isotopes and the specific $\mathrm{^{235}U}$ and $\mathrm{^{239}Pu}$ isotopes are measured with 1.3$\%$, 3$\%$ and 8$\%$ uncertainties respectively near the 3 MeV spectrum peak in reconstructed energy, reaching the best precision in the world. The total antineutrino flux and isotopic $\mathrm{^{235}U}$ and $\mathrm{^{239}Pu}$ fluxes are precisely measured to be $5.84\pm0.07$, $6.16\pm0.12$ and $4.16\pm0.21$ in units of $10^{-43} \mathrm{cm^2/fission}$. These measurements are compared with the Huber-Mueller (HM) model, the reevaluated conversion model based on the Kurchatov Institute (KI) measurement and the latest Summation Model (SM2023). The Daya Bay flux shows good consistency with KI and SM2023 models, but disagrees with HM model. The Daya Bay spectrum, however, disagrees with all model predictions.

nucl-ex↗

arXiv2025

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 ($0\nu\beta\beta$) 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 $0\nu\beta\beta$ 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 $0\nu\beta\beta$ 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↗

arXiv2025

Antenna Arrays for CRES-based Neutrino Mass Measurement

CRES is a technique for precision measurements of kinetic energies of charged particles, pioneered by the Project 8 experiment to measure the neutrino mass using the tritium endpoint method. It was recently employed for the first time to measure the molecular tritium spectrum and place a limit on the neutrino mass using a cm$^3$-scale detector. Future direct neutrino mass experiments are developing the technique to overcome the systematic and statistical limitations of current detectors. This paper describes one such approach, namely the use of antenna arrays for CRES in free space. Phenomenology, detector design, simulation, and performance estimates are discussed, culminating with an example design with a projected sensitivity of $m_β < 0.04 \ \mathrm{eV}/c^2$. Prototype antenna array measurements are also shown for a demonstrator-scale setup as a benchmark for the simulation. By consolidating these results, this paper serves as a comprehensive reference for the development and performance of antenna arrays for CRES.

physics.ins-det↗

arXiv2025

Sensitivity of the CUPID experiment to $0\nu\beta\beta$ decay of $^{100}$Mo

CUPID is a next-generation bolometric experiment to search for neutrinoless double-beta decay ($0\nu\beta\beta$) 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 $\alpha$ rejection. We compute the discovery and the exclusion sensitivity of CUPID to $0\nu\beta\beta$ 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 $\hat{m}_{\beta\beta} < \ 9.6$ -- $28 \ \mathrm{meV}$. The Frequentist discovery sensitivity (3$\sigma$) is $\hat{T}_{1/2}= 1.0 \times 10^{27} \ \mathrm{yr}$, corresponding to $\hat{m}_{\beta\beta}= \ 12$ -- $36 \ \mathrm{meV}$.

nucl-ex↗