Bulletin of the American Physical Society
2019 Fall Meeting of the APS Division of Nuclear Physics
Volume 64, Number 12
Monday–Thursday, October 14–17, 2019; Crystal City, Virginia
Session LB: Neutrino Properties |
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Chair: Nathaniel Bowden, Lawrence Livermore National Laboratory Room: Salon 2 |
Wednesday, October 16, 2019 10:30AM - 10:42AM |
LB.00001: Could deficient knowledge in the $^{\mathrm{235,238}}$U and $^{\mathrm{239,241}}$Pu antineutrino spectra explain the reactor neutrino anomaly? Alejandro Sonzogni, Ross MacFadyen, Elizabeth McCutchan The Daya Bay, Double Chooz and RENO collaborations have reported measurements of Inverse Beta Decay antineutrino spectra generated by nuclear reactors. Their results have not only confirmed an electron antineutrinos deficit of about 5{\%} at short distances with respect to our current best models, but also revealed a spectrum distortion characterized by an overprediction at the top of the spectrum and an underprediction at around 5 MeV. Our numerical accounting of the antineutrino spectrum generated by a nuclear reactor is based on the electron spectra measured by ILL for $^{\mathrm{235}}$U and $^{\mathrm{239,241}}$Pu, the conversion of these electron spectra into the corresponding antineutrino spectra and the calculation of the $^{\mathrm{238}}$U antineutrino spectrum using nuclear databases. Here we explore if uncorrelated or correlated adjustments to the spectra of these four fissile isotopes are consistent with the data available, by describing the evolution of the adjusted models as a function of fuel burnup and comparing the adjusted antineutrino spectra to their corresponding electron ones via a novel reverse conversion process. [Preview Abstract] |
Wednesday, October 16, 2019 10:42AM - 10:54AM |
LB.00002: Antineutrino Spectra and Decay Heat Measurements with the Modular Total Absorption Spectrometer Bertis Rasco Nuclear reactors are the largest man-made source of $\bar{\nu}}$s and as such they are excellent sources to directly measure $\bar{\nu}}$s. The predicted $\bar{\nu}}$ flux from nuclear reactors is not precisely known. One way to predict the $\bar{\nu}}$ flux, the summation method, requires precise knowledge of the $\beta$ decays of the many fission products. Because all reactor antineutrinos are created from $\beta$-decaying fission products it is imperative to experimentally measure these $\beta$ decays. In addition to producing a precise prediction of the $\bar{\nu}}$ flux, a proper understanding of the $\beta$ decay of fission products produced in nuclear reactors is important in order to understand how the decay heat energy is shared between $\gamma$ rays, $\beta$ rays, neutrons, and $\bar{\nu}}$s. The improved $\beta$ decay information influences reactor safety, and the decay back to stability of the r process. In this talk we present an overview of the latest results from the Modular Total Absorption Spectrometer Collaboration and its impact on the predicted $\bar{\nu}}$ flux from nuclear reactors. [Preview Abstract] |
Wednesday, October 16, 2019 10:54AM - 11:06AM |
LB.00003: Nuclear Structure Decay Studies for Reactor Antineutrino Physics E.A. McCutchan, S. Zhu, K. Auranen, A.A. Sonzogni, K. Kolos, N.D. Scielzo, M.P. Carpenter, G. Savard, J. Clark, A. Gula There are several intriguing features involving recent measurements and calculations of reactor antineutrino spectra including a deficient in the total number of measured antineutrinos, a spectra distortion in the region of 5-7 MeV antineutrino energy, and a fine structure which can be attributed to the decay of just a few out of the total 800 fission fragments making up the spectra. A full understanding of these aspects requires a solid basis of the underlying nuclear physics, namely the beta-decay properties of fission fragments used as inputs to calculate the spectra. Using the CARIBU facility at Argonne National Laboratory, we have performed new measurements on several key isotopes including $^{\mathrm{92}}$Rb, $^{\mathrm{142}}$La, and $^{\mathrm{141}}$Cs. The decay of $^{\mathrm{92}}$Rb was studied with the SATURN array, while the decays of $^{\mathrm{142}}$La and $^{\mathrm{141}}$Cs were observed with the Gammasphere array. The results of these analyses will be presented and their impact on reactor antineutrino calculations will be discussed. [Preview Abstract] |
Wednesday, October 16, 2019 11:06AM - 11:18AM |
LB.00004: Addressing Nuclear Data Needs with the PROSPECT Antineutrino Measurements Thomas Langford The PROSPECT experiment at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Lab has recently published the first modern measurement of the energy spectrum from $^{235}$U antineutrinos from a highly-enriched uranium reactor. With more than 30,000 detected antineutrino interactions, the PROSPECT spectrum uses six times higher statistics than the only previous measurement at the ILL reactor in 1981. Combined with the high-precision studies of Daya Bay and other medium baseline experiments at LEU reactors, the measurements of PROSPECT have stimulated the use of reactor antineutrinos to address nuclear data needs. We will discuss the recent antineutrino measurements with PROSPECT and their relevance for the evaluation of nuclear data. [Preview Abstract] |
Wednesday, October 16, 2019 11:18AM - 11:30AM |
LB.00005: TRISTAN project - To search for keV-scale sterile neutrino with KATRIN Yung-Ruey Yen A viable candidate for dark matter, keV-scale sterile neutrinos would be detectable from their distinct distortion of the beta-decay spectrum. The KArlsruhe TRItium Neutrino (KATRIN) experiment has recently started its precision measurement of the endpoint spectral shape of the tritium beta-decay to directly probe the neutrino mass. To eventually take advantage of the KATRIN beamline, particularly the high luminosity tritium source, the TRISTAN project is currently an R{\&}D effort to develop a new detector system optimized for the keV-scale sterile neutrino search where the measurement ~has to cover the entire tritium beta-decay spectrum energy range. This talk will discuss the design requirements for the TRISTAN detector as well as the latest results from the prototypes. [Preview Abstract] |
Wednesday, October 16, 2019 11:30AM - 11:42AM |
LB.00006: Phase II of the Project 8 neutrino mass experiment using Cyclotron Radiation Emission Spectroscopy Elise Novitski Project 8 is a neutrino mass experiment that uses a new technique, Cyclotron Radiation Emission Spectroscopy (CRES), to make a differential measurement of the tritium $\beta^{-}$ spectrum. Project 8 aims to use the advantages of CRES to overcome the systematic and statistical limitations of current-generation direct measurement methods. It will proceed in a phased approach toward a goal of effective electron antineutrino mass sensitivity of ${\sim}$40 meV/c$^2$. This talk will introduce CRES and Project 8, and will report on recent Phase II results. These include systematic studies using monoenergetic conversion electrons from $^{83m}$Kr, as well as analysis progress and preliminary data from the ongoing final Phase II molecular tritium spectrum measurement, which is the first continuous spectrum measured using CRES. [Preview Abstract] |
Wednesday, October 16, 2019 11:42AM - 11:54AM |
LB.00007: Modeling Transmitting Antennas to Simulate Phase-III of the Project 8 Experiment Pranava Teja Surukuchi Project 8 is an experiment designed to measure the mass of the electron neutrino using cyclotron radiation emission spectroscopy~(CRES). Using the cyclotron frequency as a proxy for kinetic energy, the experiment aims to observe the end point of the electron spectrum of tritium beta-decay in an effort to reach neutrino mass sensitivity of 40 meV/c$^2$. Following the successful demonstration of CRES with a waveguide in Phase I and II, the Phase III of Project 8 will utilize a larger experimental volume instrumented with a phased array of antennas. Room temperature lab measurements using antennas for both transmission and reception can be used to test the Phase III design and make a comparison with numerical predictions using the Locust simulation software. We discuss the simulation work on modeling the transmission and detection using antenna of radiation near 26 Ghz for the successful reconstruction of the beta decay electron kinematics in Phase III. [Preview Abstract] |
Wednesday, October 16, 2019 11:54AM - 12:06PM |
LB.00008: Time-domain Simulation of RF Antenna Response in the Project 8 Experiment Arina Telles The Project 8 experiment aims to directly measure the neutrino mass down to $\sim$ 40~meV/c$^2$ by reconstructing the kinematics of tritium beta decay, using a novel technique called cyclotron radiation emission spectroscopy (CRES). In this method, the electron source is placed in a uniform 1~T magnetic field and its cyclotron frequency is used to infer its kinetic energy. The distortion at the endpoint of its energy spectrum then constrains the effective neutrino mass. This technique has been demonstrated on a small scale in waveguides to detect radiation from single electrons. The next phase of the experiment (Phase III) will move to larger volume to increase sensitivity, requiring implementation of CRES in a free-space radiation environment. Feasibility will require detection of a 1~fW signal near 26~GHz. Accurate simulations are necessary to model the reception and transmission of this faint signal and to test electron energy reconstruction. In this talk we will describe time-domain modeling of microstrip antennas for the Phase III detector. A selection of antenna responses from the Locust simulation software are compared with results from commercial high-frequency simulations (ANSYS HFSS), and are applied toward CRES electron simulations. [Preview Abstract] |
Wednesday, October 16, 2019 12:06PM - 12:18PM |
LB.00009: Overview of atomic tritium efforts within Project 8 Lucie Tvrznikova Neutrino flavor oscillation experiments prove that neutrinos have nonzero masses, but cannot determine the absolute mass scale. To address this question, the effective mass of the electron antineutrino $m_{\overline{\nu}_{e}}$ can be determined from a sufficiently high-precision measurement of the tritium beta-decay spectrum around its endpoint (Q = 18.6 keV). Project 8 is a next-generation experiment using the novel Cyclotron Radiation Emission Spectroscopy (CRES) technique to perform a radio-frequency-based measurement of the decay electron energy. To achieve its design sensitivity of $m_{\overline{\nu}_{e}}\sim40$ meV, Project 8 will use an atomic tritium source to eliminate rotational and vibrational excitations of molecular tritium that perturb the tritium spectrum endpoint. The collaboration is developing techniques needed to produce, cool, and trap atomic tritium compatible with CRES. These efforts include testbeds to characterize the efficiency of production, formation, magnetic focusing, and cooling of a hydrogen, deuterium, and later tritium beam for injection into an atomic trap. I will present the latest progress toward atomic tritium within the collaboration. [Preview Abstract] |
Wednesday, October 16, 2019 12:18PM - 12:30PM |
LB.00010: Hardware Design for Atomic Tritium in Project 8 Alec Lindman Project 8 is a phased experiment using tritium beta decay to investigate the absolute neutrino mass. Good energy precision, high statistics, and well-controlled systematics are required to reach $m_{\bar \nu_e}\leq$ 40 meV. Our technique, Cyclotron Radiation Emission Spectroscopy, has already achieved eV-scale resolution at 17.8 keV, near the tritium endpoint. Project 8 was the first to observe the fW-scale cyclotron radiation from individual electrons. The event rate in a CRES experiment scales with volume; we will instrument our fiducial volume with a spatially-resolving antenna array, eliminating pileup even at high activity. Project 8 will be the first laboratory neutrino mass experiment to use atomic tritium. A decay in a tritium molecule excites rovibrational states that smear the observed energy by ~ 1 eV. The decay of atomic tritium, however, has an energy smearing of just 0.1 eV. Our baseline design calls for trapping the 30 mK atomic tritium in a 2 T-deep, 10+ m$^3$ superconducting magnetic bottle. I will discuss our phased approach to building this large-volume atomic tritium CRES experiment, with emphasis on demonstration of production and handling techniques for the recombination-prone tritium atoms. [Preview Abstract] |
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