Bulletin of the American Physical Society
Fall 2022 Meeting of the APS Division of Nuclear Physics
Volume 67, Number 17
Thursday–Sunday, October 27–30, 2022; Time Zone: Central Daylight Time, USA; New Orleans, Louisiana
Session PD: Neutrinos III: Sterile Neutrinos and the Reactor Antineutrino Anomaly |
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Chair: Dan Salvat, Indiana University Room: Hyatt Regency Hotel Celestin B |
Sunday, October 30, 2022 10:30AM - 10:42AM |
PD.00001: The Final U-235 Reactor Antineutrino Spectrum Result from PROSPECT-I Xiaobin Lu PROSPECT, the Precision Reactor Oscillation and SPECTrum Experiment, is a short-baseline reactor-based neutrino experiment aiming to make a precision measurement of reactor antineutrino energy spectra and model-independently search for eV-scale sterile neutrinos. The experiment collected over 50,000 neutrino interactions over the course of five reactor-on cycles at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory in 2018 using the PROSPECT-I detector. This data collection was impacted by a gradually increasing number of in-operative PMTs. Here we report on new analysis methods that use single-PMT segments for background rejection and time period subdivision to better utilize double-PMT segments. Combined, these methods yield an increase in the statistical power of the data by about a factor of two. This talk will present the final PROSPECT-I U-235 antineutrino spectrum result, which requires a multi-period unfolding to account for variations in detector response, and interpretation in the context of the 'Reactor Spectrum Anomaly'. |
Sunday, October 30, 2022 10:42AM - 10:54AM |
PD.00002: The PROSPECT-II Detector Upgrade Shashank Jayakumar The Precision Reactor Oscillation and SPECTrum (PROSPECT) experiment is a short-baseline reactor experiment with the goal of measuring the antineutrino spectrum from the High Flux Isotope Reactor (HFIR). It searches for potential short-baseline oscillations and the existence of sterile neutrinos. PROSPECT has already set new limits on the existence of eV-scale sterile neutrinos while achieving the highest signal-to-background ratio on any surface antineutrino detector. Despite the achievements so far, progress remains to be made. The collaboration has developed an upgraded detector design, called PROSPECT-II, which will greatly increase collected antineutrino statistics and physics sensitivity. Building off successful elements of the first PROSPECT-I detector, this upgrade will improve robustness and reliability to ensure long-term stable operation and allow the possibility of relocation to different reactor types. This presentation will describe the design of the PROSPECT-II detector and its expected performance. |
Sunday, October 30, 2022 10:54AM - 11:06AM |
PD.00003: PROSPECT-II Physics Goals Manoa Andriamirado PROSPECT, the Precision Reactor Oscillation and SPECTrum Experiment, is a reactor antineutrino experiment at a very short baseline designed to search for sterile neutrino oscillation as well as to measure antineutrino energy spectrum from 235U. The PROSPECT experiment has reported considerable Physics results, namely: demonstrated a decent signal-to-background ratio capabilities for an on-surface detector, set strong limits on eV-scale sterile neutrino oscillation search and a precise measurement of the 235U antineutrino energy spectrum. The PROSPECT collaboration is planning for PROSEPCT-II, an upgraded version of PROSPECT-I in order to ameliorate the recent Physics results and help solving neutrino anomalies along the way. A two year deployment at HFIR, will extend PROSPECT-II’s sterile neutrino sensitivity allowing the resolution of CP-violation ambiguity at long baseline experiment. At the same time, it will improve the measurement of the 235U antineutrino spectrum and make a measurement of the absolute 235U antineutrino flux allowing for detailed studies of discrepancies between theoretical models and experimental data. On top of that, a deployment at a low-enriched Uranium reactor is also envisioned to increase sensitivity coverage at below 3-eV2 as well as to study the neutrinos yield from other fission isotopes. |
Sunday, October 30, 2022 11:06AM - 11:18AM |
PD.00004: Analysis of the Reactor Antineutrino Spectrum Using Gamma Rays Samuel Kim, C J Martoff, Mike Dion, David Glasgow Recent electron anti-neutrino measurements have shown a spectral bump in the 5 to 7 MeV region that is not predicted by the β- conversion method based on the high-resolution iron-core electron spectrometer (BILL) measurements. Using the summation method along with the ENDF/B.VII.1 fission yield library and ENSDF decay data library, Dwyer and Langford have pointed out that several specific beta-decaying nuclides are a possible source for this bump. To explore this possibility, 253 nanogram of Uranium 235 sample was irradiated using HFIR for 30 seconds. Subsequently, the gamma ray spectrum was measured for 30 seconds using an ORTEC P-type 44% relative efficiency HPGE. The strongest gamma ray emitted from each of the suggested nuclides has been quantified using a non-linear peak fitting method. The expected yields were calculated using the JEFF-3.3 fission yield library and ENDSF decay data library. The measured gamma ray yields were shown to be within 2-sigma of the expected values for 96-Y, 100-Nb, 95-Sr, 140-Cs and 93-Rb. These results indicate that the spectral bump produced by the summation method could be due to incorrect fission yield values in ENDF/B.VII.1. |
Sunday, October 30, 2022 11:18AM - 11:30AM |
PD.00005: Spatiotemporal Energy Relaxation Simulation in Superconducting Tunnel Junction Detectors Connor Bray The BeEST experiment uses Superconducting Tunnel Junction (STJ) radiation detectors to search for sub-MeV neutrino mass states by precisely measuring the daughter recoil energy following the EC decay of 7Be. In order to improve the modeling of the energy response of STJ sensors, we are developing detailed spatiotemporal Monte-Carlo simulations of the energy relaxation process within the detector. The goal is to understand the non-equilibrium physics by reproducing the measured response of the sensors. In particular, the simulations aim to model the physical processes that create observed low-energy tails, line splitting artifacts, and other effects that can limit the sensitivity of the sterile neutrino search. This talk presents recent progress and comparison with experimental data. |
Sunday, October 30, 2022 11:30AM - 11:42AM |
PD.00006: Quantifying Signal Readout Non-Linearity for the BeEST Experiment Andrew Marino The BeEST experiment uses superconducting tunnel junction (STJ) radiation detectors to investigate the electron-capture decay of 7Be to search for sub-MeV neutrino mass states. We have developed a LabView code for an NI PXIe-5423 arbitrary waveform generator to simulate STJ signals with an amplitude distribution expected as the output of this experiment. This code is used to quantify systematic uncertainties in the readout chain of the BeEST experiment such as non-linearities in the analog-to-digital converters or channel-to-channel variations. In addition, arbitrary sterile neutrino mixing can be injected into the BeEST spectrum to test the sensitivity of our analysis code to various sterile neutrino masses and mixing angles. |
Sunday, October 30, 2022 11:42AM - 11:54AM |
PD.00007: First direct measurement of the 7Be electron capture Q value using Penning trap mass spectrometry Ramesh Bhandari, Georg Bollen, Nadeesha D Gamage, Alec S Hamaker, Madhawa H Gamage, Kyle G Leach, Daniel Puentes, Matthew Redshaw, Ryan Ringle, Stefan Schwarz, Chandana Sumithrarachchi, Isaac T Yandow, Zachary Hockenbery The Beryllium Electron capture in Superconducting Tunnel junctions (BeEST) experiment is searching for the signature of sterile neutrinos via momentum reconstruction in the electron capture (EC) decay of 7Be. In EC decay, there are only two final state products, the daughter atom, and neutrino. Rather than having an energy distribution of final products, as is the case with beta decay, in EC decay the neutrino and recoiling daughter atom have well defined energies that depend on the kinematics of the decay. In the case of 7Be EC decay, the ground-state to ground-state Q-value of 861.89(71) keV results in a recoil energy for the 7Li daughter atom of 56.83(1) eV. Although the uncertainty in the recoil energy is only 10 meV, this is already comparable to the uncertainty in the 7Li recoil energy obtained in Phase II operation of the BeEST experiment. A new, direct measurement of the 7Be Q value is called for to check its accuracy, to reduce the uncertainty for a meaningful check of systematics in the BeEST experiment, and to meet the anticipated precision of the 7Li recoil energy in future Phases of BeEST operation. We have performed such a measurement via Penning trap mass spectrometry to determine the mass ratio of 7Be+/7Li+ using the LEBIT facility at the National Superconducting Cyclotron Laboratory. Our preliminary result indicates a reduction in uncertainty compared to the current value of about a factor of three. This result will impact the analysis of current and future data obtained with the BeEST. |
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