arXiv subjects

Michael Heines

Publications and source records attributed to Michael Heines.

5 recordsLinked to original sources

arXiv2026

Cluster emission and its impact on the r-process nucleosynthesis

Cluster emission is an exotic decay mode between alpha-decay and fission, in which a parent nucleus emits a cluster of nucleons heavier than an alpha-particle, but lighter than what is usually considered a fission fragment. The properties of cluster emission were investigated by analyzing five high-energy events detected in a spectrum of a mass A = 230 beam produced at ISOLDE (CERN). Under the assumption that these events were caused by cluster emission, the most likely parent-cluster pair responsible for the five high-energy events, was found to be $^{230}Ra$ emitting $^{22}O$, with a branching ratio of $(4.3$ +\- $1.9) \times 10^{-9}$. Four analytical formulas were used to estimate the partial half-lives of cluster emission for a group of neutron-rich nuclei. The decay rate was calculated for a selection of cluster nuclei for each parent isotope. The rates of all decay channels of cluster emission per parent nucleus were then included in calculations of the r-process nucleosynthesis in a neutron star merger in order to study the possible impact of cluster emission on the r-process nuclear production. The resulting isotopic abundance distributions were compared to those calculated for a case in which cluster emission was not considered. It was found that the inclusion of cluster emission decay rates from the simple analytical formulas available nowadays does not influence the results of the r-process nucleosynthesis.

nucl-ex↗

arXiv2026

Nuclear Charge Radius of $^9$Be from Muonic Atom Spectroscopy Using a Microcalorimeter

The $2p\to1s$ transition energy in muonic $^9$Be was measured using a metallic magnetic calorimeter, resulting in $E_{2p\to 1s}=33\,391.48(34)\,$eV. The result is 30 times more precise than the previous best measurement and enables the extraction of the corresponding nuclear charge radius $r_c($$^9$Be$)=2.5506(51)\,$fm. It is $2.4$ times more precise than the commonly used value based on electron scattering and differs from it by $2.3$ times the combined uncertainties. This measurement represents the first determination of a nuclear charge radius using muonic x-ray spectroscopy with microcalorimeters.

nucl-ex↗

arXiv2024

The MONUMENT Experiment: Ordinary Muon Capture studies for 0$\nu\beta\beta$ decay

The MONUMENT experiment measures ordinary muon capture (OMC) on isotopes relevant for neutrinoless double-beta (0$\nu\beta\beta$) decay and nuclear astrophysics. OMC is a particularly attractive tool for improving the theoretical description of 0$\nu\beta\beta$ decay. It involves similar momentum transfers and allows testing the virtual transitions involved in 0$\nu\beta\beta$ decay against experimental data. During the 2021 campaign, MONUMENT measured OMC on $^{76}$Se and $^{136}$Ba, the isotopes relevant for next-generation 0$\nu\beta\beta$ decay searches, like LEGEND and nEXO. The experimental setup has been designed to accurately extract the total and partial muon capture rates, which requires precise reconstruction of energies and time-dependent intensities of the OMC-related $\gamma$ rays. The setup also includes a veto counter system to allow selecting a clean sample of OMC events. This work provides a detailed description of the MONUMENT setup operated during the 2021 campaign, its two DAQ systems, calibration and analysis approaches, and summarises the achieved detector performance. Future improvements are also discussed.

nucl-ex↗

arXiv2023

MMC Array to Study X-ray Transitions in Muonic Atoms

The QUARTET collaboration aims to significantly improve the precision of the absolute nuclear charge radii of light nuclei from Li to Ne by using an array of metallic magnetic calorimeters to perform high-precision X-ray spectroscopy of low-lying states in muonic atoms. A proof-of-principle measurement with lithium, beryllium and boron is planned for fall 2023 at the Paul Scherrer Institute. We discuss the performance achieved with the maXs-30 detector module to be used. To place the detector close to the target chamber where the muon beam will impact the material under study, we have developed a new dilution refrigerator sidearm. We further discuss the expected efficiency given the transparency of the X-ray windows and the quantum efficiency of the detector. The expected muonic X-ray rate combined with the high resolving power and detection efficiency of the detector suggest that QUARTET will be able to study the de-excitation of light muonic atoms at an unprecedented level, increasing the relative energy resolution by up to a factor of 20 compared to conventional detector techniques.

physics.ins-det↗

arXiv2023

Towards Precision Muonic X-Ray Measurements of Charge Radii of Light Nuclei

We propose an experiment to measure the nuclear charge radii of light elements with up to 20~times higher accuracy. These are essential both for understanding nuclear physics at low energies, and for experimental and theoretical applications in simple atomic systems. Such comparisons advance the understanding of bound-state quantum electrodynamics and are useful for searching for new physics beyond the Standard Model. The energy levels of muonic atoms are highly susceptible to nuclear structure, especially to the mean square charge radius. The radii of the lightest nuclei (with the atomic number, $Z=1,2$) have been determined with high accuracy using laser spectroscopy in muonic atoms, while those of medium mass and above were determined using X-ray spectroscopy with semiconductor detectors. In this communication, we present a new experiment, aiming to obtain precision measurements of the radii of light nuclei $3 \leq Z \leq 10$ using single-photon energy measurements with cryogenic microcalorimeters; a quantum-sensing technology capable of high efficiency with outstanding resolution for low-energy X-rays.

physics.atom-ph↗