Research

The beest: neutrino Studies using Be-7 EC DEcay and superconducting quantum sensors

The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) [pronounced “beast”] experiment searches for keV-scale sterile neutrino dark matter and a determination of the absolute neutrino mass scale.  This is possible using the electron capture decay of unstable Be-7 nuclei implanted into superconducting tunnel junction radiation detectors that are able to provide eV-level (or better) energy resolution on the Li-7 nuclear-recoil kinetic energies. This is performed by implanting Be-7 directly into these sensitive detectors at TRIUMF-ISAC in Vancouver, Canada, and the experiments are performed at Lawrence Livermore National Laboratory in California.  The program has already completed the  Phase-I proof-of-concept measurement, and is in progress on Phase-II and the neutrino mass determination.

Research opportunities at the BS, MS, and PhD levels are currently available for this project.

Current Team:
Project Spokesperson: Prof. Kyle G Leach (Mines)
Laboratory Lead / Project PI : Dr. Stephan Friedrich (LLNL)
Student Team: Spencer Fretwell (Mines), Connor Bray (Mines)

Searching for Neutrinoless double beta decay with nexo

Many extensions of the standard model of particle physics (SM) suggest that neutrinos should be Majorana-type fermions—that is, that neutrinos are their own anti-particles—but this assumption is difficult to confirm. Observation of neutrinoless double-β decay (0νββ), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. The nEXO concept is based on a Time Projection Chamber (TPC) filled with five tonnes of liquid xenon (LXe) enriched to 90% Xe-136. This choice is directly derived from the success of the EXO-200 experiment and is motivated by the ability of large homogeneous detectors to identify and measure background and signal simultaneously.  Our local group at Mines is a member of the nEXO collaboration, and is heavily involved in several working groups.

Research opportunities at the BS, MS, and PhD levels are currently available for this project.

Current Team (nEXO Collaboration):
Project Spokesperson: Prof. Giorgio Gratta (Stanford)
Chief Scientist: Dr. Mike Heffner (LLNL)

Mines Team: Prof. Kyle G Leach (Institutional Lead), Connor Natzke

nuclear excitation via electron capture (NEEC) with the titan-ebit at triumf

Nuclear Excitation via Electron Capture (NEEC) is the inverse process of internal electron conversion, where a free electron is captured into an atomic vacancy simultaneously exciting the nucleus to a higher-energy state. This interaction between the nuclear volume and the atomic electrons occurs by either Coulomb interaction or virtual photon exchange between the electronic and nuclear currents. Unlike broadband photoexcitation of isomers with bremsstrahlung photons, however, NEEC is a resonant process, and thus requires specific energy matching where the sum of the kinetic energy of the free electron and captured binding energy must correspond to the energy difference between the initial and final nuclear states. This results in the need for strong atomic charge-state control over the sample, as well as careful case selection of nuclear states that may be compatible with efficient electron recombination.  As a result, we perform such measurements in the Electron Beam Ion Trap (EBIT) which is part of the TITAN experiment at TRIUMF in Vancouver, Canada.  NEEC has been investigated as one of the most promising sources for possible nuclear battery technologies, which could provide energy densities 100,000 times greater than those in traditional chemical batteries.  This work is part of the TITAN scientific program, and is currently being led by the team at TRIUMF and the Colorado School of Mines. 

Current Team:
Project Spokespersons: Dr. Iris Dillmann (TRIUMF), Dr. Ania Kwiatkowski (TRIUMF), Prof. Kyle G Leach (Mines)
Student Team: Jon Ringuette (Mines)

testing ckm unitarity and searching for exotic weak currents via superallowed fermi beta decay

There is an intense ongoing focus on experimental and theoretical studies of superallowed 0+0+ nuclear β decays. This class of β decay currently provides the most precise determination of the vector coupling constant for weak interactions, GV, which is vital in the extraction of the up-down element of the Cabibbo-Kobayashi-Maskawa (CKM) quark-mixing matrix, Vud. Since precision testing of the standard model is heavily dependent on Vud, the importance of accurate superallowed Ft-values is crucial. In order to extract Vud from the high-precision experimental data, corrections to the almost nucleus-independent ft-values for superallowed β decays must be made for radiative effects as well as isospin-symmetry-breaking (ISB) by Coulomb and charge-dependent nuclear forces. Although these corrections are small (1%), experimental measurements have provided such precise ft-values (±0.03%) that the uncertainty on GV is dominated by the precision of these theoretical corrections.  Due to the significant effect these ISB calculations have on the extraction of Ft, the theoretical models must be extensively tested against high-quality experimental data. Superallowed Fermi β-decay systems have also been explored as a venue for the possible observation of scalar contributions to the weak interaction.  Our group is currently involved in direct precision measurements of these nuclear decays, as well as detailed nuclear structure measurements related to evaluating the ISB corrections that are required to test the Standard Model from such measurements.

Current Team:
PI: Prof. Kyle G Leach
Student Team: Matthew Martin (Mines)
Key Collaborators: Prof. Carl Svensson (Guelph), Dr. Jason Holt (TRIUMF), Dr. Ragnar Stroberg (U Washington), Prof. Gwen Grinyer (U Regina), Prof. Paul Garrett (Guelph), Dr. Gordon Ball (TRIUMF), Prof. Hamish Leslie (Queen’s), Prof. Maxime Brodeur (Notre Dame), Prof. Jens Dilling (TRIUMF), Dr. Ania Kwiatkowski (TRIUMF)