Session MM: Undergraduate Research III

Argon-42 Production for LEGEND: the search for 0??????​

The LEGEND-1000 experiment is a ton-scale search for neutrinoless double beta decay that will consist of Germanium semiconductor detectors submerged in a liquid Argon cryogen. A leading background comes from the beta decay of ⁴²K, a daughter of ⁴²Ar, which is produced in cosmic ray collisions in the upper atmosphere. LEGEND-1000 seeks to understand the flow patterns of ⁴²Ar in the liquid, their collection on the charged surfaces of the detectors, and the resulting background from the beta decay after it penetrates the dead layer of the germanium crystal. This talk presents the first results of ⁴²Ar production at the Tandem accelerator located at the Triangle Universities Nuclear Laboratory in order to study its behavior, using the drop-off reaction of (⁴He, ⁴⁰Ar)⁴²Ar.    

Electrons for Neutrinos: Analysis of the 1p1pi Channel

Neutrino oscillation is of particular interest to experiments around the world. The oscillation of the neutrino is measured as a function of the particle's energy divided by propagation distance. This energy (E), however, is not directly measurable and must instead be reconstructed from the momenta of particles knocked out during neutrino-nucleus interactions. In order to test this energy reconstruction, we exploited the similarity between electron-nucleus and neutrino-nucleus interactions using electron-nucleus scattering data collected by the large-acceptance CLAS6 detector at the Thomas Jefferson National Accelerator Facility. This presentation will focus on the resonance dominated 1p1pi channel and we will present results on pi+ and pi- and compare them to Genie calculations. This data will be used to guide improvements in current event generators which are important to meet the requirements of high-precision experiments currently underway at facilities such as MicroBooNE, MINERvA, DUNE, and T2K.   

Search for Lightly Ionizing Particles in CUORE

The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale TeO2 bolometer array operating at a temperature of approximately 10mK. Though CUORE's primary objective is the search for neutrinoless double beta decay, its low energy thresholds and high exposures allow for searches for other rare decays, dark matter, and physics beyond the Standard Model (BSM). Most recently, the development of improved track reconstruction techniques has enabled searches for exotic track-like particles in CUORE. In this talk, we present a direct detection search for a class of BSM particles known as lightly ionizing particles (LIPs), whose charge (q = e/f) is reduced by a factor of f relative to the electron charge. LIPs can be identified by their muon-like tracks but have distinctive energy signatures that result from suppressed interactions with matter. This talk discusses analysis methods and recent progress in the search for lightly ionizing particles within CUORE.   

Revealing the nuclides that shape the high-energy Daya Bay antineutrino spectrum

The Daya Bay collaboration just released their reactor antineutrino spectrum in the 8 to 11 MeV region. While the Huber model for ²³⁵U and ^239,241Pu could be valid for antineutrino energies up to 8.5 MeV, its reliability above 7 MeV rapidly declines due to high uncertainty and dispersion in the corresponding electron spectra. Thus, our only tool to study this newly-published spectrum is the summation model, which adds the antineutrino spectra of every fission product weighted by their corresponding cumulative fission yield. But since few fission products may significantly contribute to the summation model at such high energies, many of which are neutron-rich with high β^- Q-values and very short-half lives, this high-energy data is of great analytical interest. In this work, using nuclear databases available at the  National Nuclear Data Center at Brookhaven National Lab, we identified the main fission products contributing to the antineutrino spectrum above 8 MeV, including a subset for which only theoretical spectra are available. We then devised a parametrization for each fission product’s decay scheme to produce the most energetic possible antineutrino spectrum for a sensitivity study, which could guide future experiments (using, for instance, the Total Absorption Spectroscopy technique).   

Identifying Key 239,241Pu Fission Products to Reexamine for the Electron Antineutrino Energy Spectrum with the Summation Model

The latest series of nuclear reactor antineutrino experiments, (Daya Bay, Double Chooz, RENO, NEOS), have consistently demonstrated a discrepancy based on the current model of choice, the Huber-Mueller model. Each measurement found an unexplained 6% deficit in their antineutrino spectra. The model itself was derived from the integral electron spectra of 235U and 239,241Pu measured at the Institut Laue-Langevin (ILL). But in light of the recent publication on the 235U/239Pu spectra ratio by Kopeikin and collaborators, the Huber-Mueller model could have a normalization issue stemming from the original ILL measurements. For an entirely different method of determining antineutrino spectra, we used the summation model. Summation utilizes fission yield data from all the fission products of 235U and 239,241Pu to produce electron spectra. But not all data is of good quality due to cost, time, and difficulty for each and every fission product. In such a predicament, our group sought to identify several key nuclei that should be remeasured with high fidelity to produce antineutrino spectra. We began with electron spectrum data measured at ORNL and proceeded to use it to benchmark the JEFF-3.3 fission yields. Electron spectra were measured at regular time intervals for a short 1-second, medium 5 or 10 seconds, and long 50 or 100 seconds, thermal neutron irradiations. Because of the time dependence, the data was not only sensitive to the fission products' electron spectrum but also to their half-lives. In doing so, we could precisely identify nuclei with significant error and contribution.   

Recovering gamma spectra data and understanding their value for nuclear reactor antineutrinos

Electron and gamma-ray spectra from the neutron induced fission products of 235U, 239Pu, and 241Pu were measured at Oak Ridge National Laboratory (ORNL) in the 1970s. This data was only published in ORNL reports, while 235U data was available in PDF formats. In this project, we digitized the gamma-ray spectra and the detector response function. This allowed us to compare the gamma-ray spectra and the detector response function with the results of the original calculations using the JEFF-3.3 fission yield sub-library and ENDF/B - VIII.0 decay data sub-library. The gamma spectra are particularly useful to understand possible deficiencies in the aforementioned sub-libraries, and they provide a consistency check with nuclear reactor antineutrino summation calculations due to the energy-wise competing nature of gammas with electrons and electron-antineutrinos.   

Benchmarking 235U independent fission yields using electron spectra data measured at ORNL to quantify nuclear decay heat for Loss of Coolant Accident scenarios

The current best estimates of the antineutrino spectrum produced by nuclear reactors are obtained from the Huber-Mueller model, which for 235U are derived from the integral electron spectra measured at the Institut Laue-Langevin (ILL). However, the latest generation of nuclear reactor antineutrino experiments – Daya Bay, Double Chooz, NEOS and RENO – have revealed a 6% deficit with respect to this model, a finding which has become known as the Reactor Antineutrino Anomaly. An alternate method to calculate the antineutrino spectrum is to use fission yields and nuclear decay databases, which has become even more relevant in view of the normalization issue with the ILL measurements brought to light in a recent publication of the 235U spectra ratio by Kopeikin and collaborators. The electron spectrum data measured at ORNL was used to benchmark the JEFF-3.3 fission yields, and these data are sensitive to both the fission products' electron spectrum and their half-lives. 235U was specifically examined because it has the biggest contribution to the overall antineutrino spectrum, and we were able to identify about ten key fission products whose fission yields would merit a precise re-evaluation and eventually a measurement.   

NMR with Machine Learning

Constant current continuous wave Nuclear Magnetic Resonance (NMR) has been an essential tool for polarized target experiments in Nuclear and High-energy physics. Q-meter based phase-sensitive detection can provide accurate monitoring of the polarization over the course of a scattering experiment with limitations due to some operational parameters. In this talk, we present recent studies of improved signal to noise in NMR-based Spin-1 polarization measurements as well as reliable measurements outside of the designated range of the Q-meter's operational parameters with the use of machine learning (ML). This approach will allow for real time online polarization monitoring and offline polarization data analysis for improved overall figure of merit for experiments using solid state polarized targets.