arXiv subjects

K. R. Woo

Publications and source records attributed to K. R. Woo.

5 recordsLinked to original sources

arXiv2026

LiFE-SNS: LiF Experiment for keV-scale Sterile Neutrino Search

The LiF Experiment for keV-scale Sterile Neutrino Search (LiFE-SNS) aims to probe sterile neutrinos through precision measurements of the tritium $β$ spectrum. Tritium nuclei are produced and embedded in LiF crystals via the ${}^{6}\mathrm{Li}(n,α){}^{3}\mathrm{H}$ reaction, allowing thermal calorimetric detection of $β$ decays with magnetic microcalorimeters (MMCs) operated at millikelvin temperatures. We present the detector configuration, background studies, and calibration method, including modeling of position-dependent response and characterization of detector nonlinearity. We also discuss potential sources of systematic uncertainty relevant to the sterile-neutrino search. While the first phase of LiFE-SNS has been completed, this paper focuses on calibration and detector characterization. The achieved performance enables precision $β$-spectrum measurements, and projected sensitivities indicate competitive reach in the keV mass region.

hep-ex↗

arXiv2025

The measurement of the $^{99}$Tc $β$-decay spectrum and its implications for the effective value of weak axial coupling

Measurements of $β$-spectral shapes is an important way to examine the effective value of the weak axial coupling $g_{\rm A}$. These stu\ dies focus specifically on forbidden non-unique $β^-$ transitions, as only in these cases is the spectral shape directly sensitive to th\ e ratio $g_{\rm A}/g_{\rm V}$. Here, the value of the weak vector coupling constant, $g_{\rm V}$, is fixed at 1.0 according to the Conserve\ d Vector Current (CVC) hypothesis. In previous studies for the fourth-forbidden non-unique $β^-$ decays of $^{113}$Cd [J.~Kostensalo \textit{et al.}, Phys. Lett. B 822, 136652 (2021)] and $^{115}$In [A.~F. Leder \textit{et al.}, Phys. Rev. Lett. 129, 232502 \ (2022) and L. Pagnanini \textit{et al.}, Phys. Rev. Lett. 133, 122501 (2024)] a quenched value was determined for the ratio $g_{\rm A}/g_{\rm V}$ using $g_{\rm V}=1.0$. A notable exception is the recent measurement and analysis of the second-forbidden non-unique $\ β$-decay transition in $^{99}$Tc, performed by M. Paulsen \textit{et al.}, Phys. Rev. C 110, 05503(2024). Where an enhanced ratio $g_{\\ rm A}/g_{\rm V}=1.526(92)$ was suggested. To resolve this apparently contradictory situation with the effective value of $g_{\rm A}$, we hav\ e performed calculations based on the nuclear shell model (NSM) Hamiltonians glekpn, jj45pnb, and the MQPM approach with a careful considera\ tion of the small relativistic vector nuclear matrix element (sNME). The theoretical spectra were compared to the $^{99}$Tc $β$-decay sp\ ectrum by using the 4$π$ gold absorber with a Metallic Magnetic Calorimeter (MMC). In all cases, we found that the data matches well with \ reduced $g_{\rm A}$/$g_{\rm V}$ values of 1.0--1.2. Our result contradicts the previously reported measurement for $^{99}$Tc and instead sup\ ports a quenched axial coupling as reported for other isotopes.

nucl-ex↗

arXiv2024

Development of decay energy spectroscopy for radio impurity analysis

We present the development of a decay energy spectroscopy (DES) method for the analysis of radioactive impurities using magnetic microcalorimeters (MMCs). The DES system was designed to analyze radionuclides, such as Ra-226, Th-228, and their daughter nuclides, in materials like copper, commonly used in rare-event search experiments. We tested the DES system with a gold foil absorber measuring 20x20x0.05 mm^3, large enough to accommodate a significant drop of source solution. Using this large absorber and an MMC sensor, we conducted a long-term measurement over ten days of live time, requiring 11 ADR cooling cycles. The combined spectrum achieved an energy resolution of 45 keV FWHM, sufficient to identify most alpha and DES peaks of interest. Specific decay events from radionuclide contaminants in the absorber were identified. This experiment confirms the capability of the DES system to measure alpha decay chains of Ra-226 and Th-228, offering a promising method for radio-impurity evaluation in ultra-low background experiments.

physics.ins-det↗

arXiv2022

Status and performance of the AMoRE-I experiment on neutrinoless double beta decay

AMoRE is an international project to search for the neutrinoless double beta decay of $^{100}$Mo using a detection technology consisting of magnetic microcalorimeters (MMCs) and molybdenum-based scintillating crystals. Data collection has begun for the current AMORE-I phase of the project, an upgrade from the previous pilot phase. AMoRE-I employs thirteen $^\mathrm{48depl.}$Ca$^{100}$MoO$_4$ crystals and five Li$_2$$^{100}$MoO$_4$ crystals for a total crystal mass of 6.2 kg. Each detector module contains a scintillating crystal with two MMC channels for heat and light detection. We report the present status of the experiment and the performance of the detector modules.

physics.ins-det↗

arXiv2022

A lab scale experiment for keV sterile neutrino search

We developed a simple small-scale experiment to measure the beta decay spectrum of $^{3}$H. The aim of this research is to investigate the presence of sterile neutrinos in the keV region. Tritium nuclei were embedded in a 1$\times$1$\times$1 cm$^3$ LiF crystal from the $^6$Li(n,$α$)$^3$H reaction. The energy of the beta electrons absorbed in the LiF crystal was measured with a magnetic microcalorimeter at 40 mK. We report a new method of sample preparation, experiments, and analysis of $^3$H beta measurements. The spectrum of a 10-hour measurement agrees well with the expected spectrum of $^3$H beta decay. The analysis results indicate that this method can be used to search for keV-scale sterile neutrinos.

physics.ins-det↗