arXiv subjects

J. L. Newstead

Publications and source records attributed to J. L. Newstead.

5 recordsLinked to original sources

arXiv2026

Exploring Low Energy Excess in MINER with sapphire detectors using Convolutional Variational Autoencoder (CVAE)

As cryogenic detectors push toward ever-lower energy thresholds, their sensitivity is increasingly constrained by a persistent low-energy background known as the low-energy excess (LEE). We report observation of LEE in the MINER experiment using a sapphire ($\mathrm{Al_2O_3}$) detector at energies around 200 eV, with the excess reproducibly reappearing after each non-operational warm-up period. To address this limiting background, we implement an unsupervised convolutional variational autoencoder (CVAE) framework that identifies anomalous events through a reconstruction-based anomaly score. For the first time in a pulse-shape driven analysis, we uncover a significant deviation in the rise-time of LEE events relative to Monte Carlo simulated ideal signals. Using this feature, we develop a discrimination pipeline based on rise-time selection. This method achieves up to 53\% rejection of LEE events, corresponding to an expected sensitivity improvement of nearly 10\% for MINER at HFIR. These findings are consistent with a scenario in which a substantial fraction of the LEE originates from bulk-related defects or microfractures within the detector crystal, while leaving room for additional detector-related contributions. Our result provides a powerful, data-driven pathway for mitigating LEE and enhancing the discovery potential of next-generation cryogenic experiments.

physics.ins-det↗

arXiv2025

CE$ν$NS Search with Cryogenic Sapphire Detectors at MINER: Results from the TRIGA reactor data and Future Sensitivity at HFIR

We report on a search for coherent elastic neutrino--nucleus scattering (CE$ν$NS) using cryogenic sapphire (Al$_2$O$_3$) detectors deployed at the Mitchell Institute Neutrino Experiment at Reactor (MINER), located near the 1~MW$_\text{th}$ TRIGA research reactor at Texas A\&M University. The experiment operated with a primary detector mass of 72~g and achieved a baseline energy resolution of $\sim 40$~eV. Using exposures of 158~g-days (reactor-on) and 381~g-days (reactor-off), we performed a statistical background subtraction in the energy region of 0.25--3~keV. A GEANT4 simulation has been performed to understand the reactor-correlated background present in the data and it agrees with our observations. The resulting best-fit ratio of the observed CE$ν$NS rate to the Standard Model prediction after rejecting the reactor induced background from the data with the help of simulation, is $ρ= 0.26\pm 1534.74~\mathrm{(stat)} \pm 0.05~\mathrm{(sys)}$ with a significance of $0.007 \pm 0.022~\mathrm{(stat)} \pm 0.001~\mathrm{(sys)}$. This low significance indicates a high background rate at low energies. To have enhanced sensitivity, the MINER collaboration plans to relocate the experiment to the 85~MW$_\text{th}$ High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). With improved shielding, increased detector mass, and higher antineutrino flux, the upgraded setup is projected to achieve a 3$σ$ CE$ν$NS detection within 30~kg$\cdot$days of exposure.

nucl-ex↗

arXiv2025

MINER Reactor Based Search for Axion-Like Particles Using Sapphire (Al2O3) Detectors

The absence of definitive results for WIMP dark matter has sparked growing interest in alternative dark matter candidates, such as axions and Axion-Like Particles (ALPs), which also provide insight into the strong CP problem. The Mitchell Institute Neutrino Experiment at Reactor (MINER), conducted at the Nuclear Science Center of Texas A&M University, investigated ALPs near a 1 MW TRIGA nuclear reactor core, positioned approximately 4 meters away. This experiment employed cryogenic sapphire detectors with a low detection threshold (approximately 100 eV), equipped with a Transition Edge Sensor capable of detecting athermal phonons. Due to the low-background environment, we were able to exclude ALPs with axion-photon coupling and axion-electron coupling as small as $g_{aγγ} = 10^{-5}$ and $g_{aee} = 10^{-7}$, respectively. Energy depositions below 3 keV were not considered and remain blinded for our Coherent Elastic Neutrino Nucleus Scattering (CEvNS) analysis. This is the first result demonstrating the MINER experiment's potential to probe low-mass ALPs, enabled by its low-threshold detector and proximity to a reactor.

hep-ex↗

arXiv2016

Background Studies for the MINER Coherent Neutrino Scattering Reactor Experiment

The proposed Mitchell Institute Neutrino Experiment at Reactor (MINER) experiment at the Nuclear Science Center at Texas A&M University will search for coherent elastic neutrino-nucleus scattering within close proximity (about 2 meters) of a 1 MW TRIGA nuclear reactor core using low threshold, cryogenic germanium and silicon detectors. Given the Standard Model cross section of the scattering process and the proposed experimental proximity to the reactor, as many as 5 to 20 events/kg/day are expected. We discuss the status of preliminary measurements to characterize the main backgrounds for the proposed experiment. Both in situ measurements at the experimental site and simulations using the MCNP and GEANT4 codes are described. A strategy for monitoring backgrounds during data taking is briefly discussed.

physics.ins-det↗

arXiv2016

DARWIN: towards the ultimate dark matter detector

DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary goal will be to explore the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass-range, until neutrino interactions with the target become an irreducible background. The prompt scintillation light and the charge signals induced by particle interactions in the xenon will be observed by VUV sensitive, ultra-low background photosensors. Besides its excellent sensitivity to WIMPs above a mass of 5 GeV/c2, such a detector with its large mass, low-energy threshold and ultra-low background level will also be sensitive to other rare interactions. It will search for solar axions, galactic axion-like particles and the neutrinoless double-beta decay of 136-Xe, as well as measure the low-energy solar neutrino flux with <1% precision, observe coherent neutrino-nucleus interactions, and detect galactic supernovae. We present the concept of the DARWIN detector and discuss its physics reach, the main sources of backgrounds and the ongoing detector design and R&D efforts.

astro-ph.IM↗