Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session G15: Neutrino Mass and Coherent Scattering |
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Sponsoring Units: DNP DPF Chair: Noah Oblath, Pacific Northwest National Laboratory Room: Sheraton Plaza Court 4 |
Sunday, April 14, 2019 8:30AM - 8:42AM |
G15.00001: Experimental study of final states in the beta decay of molecular tritium. R G Hamish Robertson Molecular tritium serves as the source for sensitive experiments, such as KATRIN, to measure neutrino mass. Molecular excitations before and after the decay modify the spectral shape, and are determined from theory. The TRIMS (Tritium Recoil Ion Mass Spectrometer) apparatus has been constructed to make a new measurement of the branching ratio to the bound molecular ion HeT+ and other ionic final states. Two measurements of this branch made in the 1950s disagree strongly with modern theory. We will report on the performance of the completed instrument and on the analysis of data from it. |
Sunday, April 14, 2019 8:42AM - 8:54AM |
G15.00002: KATRIN: Directly probing neutrino mass via tritium beta decay Yung-Ruey Yen The KArlsruhe TRItium Neutrino experiment (KATRIN) is designed to probe the effective electron anti-neutrino mass to a projected sensitivity of 0.2 eV at the 90% confidence level. State-of-the-art technology developed by the collaboration will perform ultrahigh precision measurements of the tritium beta-decay spectrum endpoint, where the neutrino mass can be determined from the spectral shape. Molecular tritium decays in a high-luminosity windowless gaseous tritium source ahead of a magnetic guided transport system that takes the beta-electron while eliminating the backgrounds of neutral and ionic tritiums. The kinetic energy of the beta-electrons can then be measured to high-resolution by the large (10 m diameter) spectrometer that uses the MAC-E-filter design. KATRIN have started commissioning runs, including a first tritium run, with the goals of demonstrating subsystem performance and understanding systematics. This talk will give an overview of the experiment and its challenges; some of the commissioning results will also be presented. |
Sunday, April 14, 2019 8:54AM - 9:06AM |
G15.00003: Ion retention, blocking and monitoring within the KATRIN experiment Ana Paula Vizcaya Hernandez The KATRIN (KArlsruhe TRItium Neutrino) experiment aims to measure the effective neutrino mass with an unprecedented design sensitivity of 0.2% eV at the 90% confidence level. The electron antineutrino is produced in tritium beta decay together with the beta-electron and a positive ion. Magnetic fields guide charged particles through the energy-analyzing retarding spectrometers towards the KATRIN detector. The antineutrino mass can be determined by fitting the energy spectrum of the electrons near the kinematic endpoint of 18.6 keV. In this method, ions act as a background source as they further ionize residual gas and produce secondary electrons. We have tested the ion-blocking mechanisms implemented in the source and transport section, where ions are blocked with positive potentials created by ring electrodes, and found the preferred settings with the highest blocking efficiency. Some ions finally strike electrodes along the beamline, creating a current that allows us to monitor the tiny ion flux in the spectrometer section. We will share results from these tests and prospects for future operations. |
Sunday, April 14, 2019 9:06AM - 9:18AM |
G15.00004: Project 8: First Measurement of the Tritium Beta-Decay Spectrum Using CyclotronRadiation Emission Spectroscopy Ali Ashtari Esfahani Project 8 is a tritium beta-decay endpoint experiment which is planned to look for neutrino mass in the range allowed by the inverted mass hierarchy. Cyclotron radiation emission spectroscopy is the employed technique for a precise measurement of the energy of relativistic electrons. The technique was demonstrated utilizing mono-energetic conversion electrons from $^{83m}$Kr. In the most recent advance, the Project 8 collaboration measured a continuous spectrum by using tritium as the source of relativistic electrons. Here we present the recent hardware upgrades and advances in analysis tools which lead us to this first measurement of the tritium beta-decay spectrum. |
Sunday, April 14, 2019 9:18AM - 9:30AM |
G15.00005: Towards Atomic Tritium in Project 8 Eric M Machado Rotational and vibrational excitations of molecular tritium (T2) perturb the beta spectrum endpoint, which limits neutrino mass sensitivity in T2-based experiments to about 100 meV. Atomic tritium opens a path for Project 8 to reach a neutrino mass sensitivity goal of 40 meV. To that end, the collaboration is developing techniques needed to produce, cool, and trap atomic tritium in a way that is compatible with Cyclotron Radiation Emission Spectroscopy. These efforts include a hardware testbed for characterizing the beam from a custom-designed, coaxial-current hydrogen atom source. The scope of the testbed will include magnetic focusing and cooling of the beam, for eventual integration with an atomic hydrogen-trapping demonstrator. Here, progress is presented on the construction and commissioning of the atom source and hardware testbed. |
Sunday, April 14, 2019 9:30AM - 9:42AM |
G15.00006: COHERENT experiment at the Spallation Neutron Source Ivan Tolstukhin The COHERENT experiment aims to study coherent elastic neutrino nucleus scattering (CEvNS) with various nuclei using pulsed neutrinos provided by the Spallation Neutron Source at ORNL. The first observation of CEvNS was reported by the COHERENT collaboration with a 14 kg CsI detector. The present dataset with twice more statistics is being analyzed. In addition, COHERENT has a ~ 22 kg LAr detector and is planning to deploy a 2 t NaI array and a 14.4 kg p-type point-contact germanium detector array to demonstrate the characteristic N^2 dependence of the CEvNS cross section. Proposed high statistics CEvNS measurements from ton-scale detectors would open new channels to search for physics beyond the Standard Model such as non-standard neutrino interactions, accelerator produced dark matter, weak mixing angle and electromagnetic properties of neutrinos. These measurements will also provide studies of charge-current neutrino cross sections in an energy range important for supernova physics. The status of the COHERENT experiment along with the future experimental program involving the CEvNS measurements will be presented. |
Sunday, April 14, 2019 9:42AM - 9:54AM |
G15.00007: Results from a CEvNS Search with the CENNS-10 Liquid Argon Detector Matthew R Heath The COHERENT collaboration recently observed Coherent Elastic Neutrino Nucleus Scattering (CEvNS) at the Spallation Neutron Source at Oak Ridge National Lab at the 6.7σ level with 14 kg of CsI commissioned in June 2015. The next goal for COHERENT is to measure CEvNS on multiple nuclei to verify the N2 dependence of the CEvNS cross section. To that end, the roughly 25 kg single phase liquid argon detector CENNS-10 was commissioned in December 2016. CENNS-10 will provide a much lighter nucleus for CEvNS, allowing COHERENT to begin to map out the low N dependence of the CEvNS cross section. In this talk I will present results from the initial liquid argon Engineering Run ending in May 2017 as well as a first look at results from the subsequent Production Run beginning in August 2017. |
Sunday, April 14, 2019 9:54AM - 10:06AM |
G15.00008: PPC Germanium Detectors for Measuring CEvNS at the SNS Connor M Awe P-type point contact germanium detectors (PPCs) are a powerful tool for radiation detection, offering good energy resolution, low noise, and small energy thresholds. The COHERENT Collaboration plans to commission a 15-kg array of high purity, low background PPC detectors to measure coherent elastic neutrino-nucleus scattering (CEvNS) at the Spallation Neutron Source. Germanium will contribute an intermediate data point between cesium and argon in the ongoing measurement of the predicted N2 cross section dependence for CEvNS. The superior energy resolution of PPCs will also allow for the precise measurement of the CEvNS recoil spectrum. I discuss efforts to design and construct the array within the collaboration. |
Sunday, April 14, 2019 10:06AM - 10:18AM |
G15.00009: Search for Neutrino-Induced Neutron Production in Pb-208 at SNS Brandon J Becker Neutrino-nucleus interactions serve as a possible probe to study the nucleus and weak interactions. The COHERENT Collaboration seeks to observe the N2 dependence of the coherent elastic neutrino-nucleus scattering (CEvNS) and continues taking data for the precision measurement of the CEvNS cross-section for multiple nuclei. A large effort has been dedicated to understanding backgrounds present. Perhaps the most elusive is the background arising from inelastic ν-nucleus interactions in the detector shielding. Inelastic ν-nucleus interactions excite a nucleus that then de-excites by particle emission. Neutrino-induced neutrons (NIN) are of special interest because these neutrons can interact to produce nuclear recoils that mimic nuclear recoils produced by CEvNS and share the same timing distribution as CEvNS events. The cross-section for heavy nuclei such as Lead and Iron is predicted to be quite large but has not been measured and theoretical calculations have large uncertainty. NIN production on Pb is also of interest as a proposed mechanism to observe supernova neutrinos as in the HALO experiment. COHERENT is constructing and characterizing capture-gated neutron detectors for deployment in 980 kg of lead target to measure the inelastic neutrino-nucleus cross-section in Pb208. |
Sunday, April 14, 2019 10:18AM - 10:30AM |
G15.00010: Quenching Factor Measurements for Germanium Detectors at Triangle Universities Nuclear Laboratory (TUNL) Long Li, Belkis Cabrera-Palmer The Coherent Elastic Neutrino-Nucleus Scattering has been observed by the COHERENT collaboration using a 14.6-kg CsI[Na] scintillator at Oak Ridge National Laboratory. This indicates a new way to build a compact neutrino detector and unlocks new channels to test the Standard Model. One challenge is to understand the neutrino-induced low energy nuclear recoils. It is commonly known that the signals from nuclear recoils can be quenched in many types of detectors, resulting in less light or ionization. This phenomenon is referred to as the “quenching factor”. It is defined as the ratio of the signal yield from the nuclear recoils to the signal yield from comparable electron recoils with the same energy. The quenching factor highly depends on the detector materials, so different detectors require their own quenching factor measurements. The next step for the COHERENT experiment is to use different nuclear targets e.g. Ar and Ge. Aside from the COHERENT experiment, many dark matter experiments (CoGeNT, LUX, and etc.) trying to directly detect weakly interacting massive particles (WIMPs) also attempt to observe elastic scatterings between WIMPs and nuclei. In this work, we will present the quenching factor measurements for germanium detectors at TUNL in the [0.8,4.9] keVnr range. |
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