Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session G10: Tonne Scale Neutrinoless Double Beta Decay R&D II |
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Sponsoring Units: DNP DPF Chair: David Radford, Oak Ridge National Laboratory Room: Sheraton Governor's Square 12 |
Sunday, April 14, 2019 8:30AM - 8:42AM |
G10.00001: Development of NEXT-100 for Neutrinoless Double Beta Decay Searches Sereres C Johnston Neutrinoless double beta decay (0νββ) searches are sensitive to the presently unknown nature and mass of neutrinos. The Neutrino Experiment with a high-pressure Xenon Time Projection Chamber (NEXT) collaboration has designed and operated gaseous xenon detectors in order to demonstrate the suitability of this technology for 0νββ searches. The NEXT collaboration currently operates a 5 kg-scale detector at the Laboratorio Subterraneo de Canfranc (Spain) and is developing a successor expected to be completed in 2019. NEXT-100 will show the performance and scalability of high pressure gaseous xenon TPCs as a 100 kg-scale detector. This talk will describe the design and construction, as well as the expected performance, of NEXT-100. |
Sunday, April 14, 2019 8:42AM - 8:54AM |
G10.00002: Improved Sensitivity of nEXO to Neutrinoless Double Beta Decay Tyana Stiegler, Jason P Brodsky, Mike Heffner, Allen House, Samuele Sangiorgio The nEXO detector is the next generation of neutrinoless double beta decay of Xe-136. The 5-ton liquid xenon TPC detector is based on the EXO-200 experiment. The nEXO experiment has developed a baseline design with a projected half-life sensitivity two orders of magnitude greater than previous experimental results. This talk will discuss the results of the sensitivity simulation and calculation for the nEXO detector published in 2018. Improvements on the initial simulation will also be discussed. These include expanding the event reconstruction and background identification to include the skin LXe, charge and light collection, and time correlated decays. |
Sunday, April 14, 2019 8:54AM - 9:06AM |
G10.00003: Improving CUORE Sensitivity using Multi-Site events Sachinthya Wagaarachchi The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton scale experimental search for neutrinoless double beta decay (0νββ) on 130Te. The CUORE detector consists of 988 TeO2 crystals operating as cryogenic bolometers at the Gran Sasso National Laboratory (LNGS) in Italy. While simulations suggest that about 11% of 0νββ decay events will deposit energy in more than one location, the most recent CUORE results come only from the analysis of single site events. In this talk, we present the projected sensitivity improvements achievable by using multi-site events that deposit energy in more than one crystal and the analysis techniques used to reconstruct the energy and estimate backgrounds. |
Sunday, April 14, 2019 9:06AM - 9:18AM |
G10.00004: Argon Background Impact on Beyond Standard Model Physics Searches in LEGEND-200 Ryan J Hegedus The LEGEND-200 experiment combines technologies from the MAJORANA DEMONSTRATOR and GERDA experiments in the search for neutrinoless double beta decay (0νββ) in the 76Ge isotope. A key technology is the use of liquid argon (LAr), in which bare 76Ge-enriched detectors are submerged, as a shield against external radioactivity. A drawback to using natural LAr is its intrinsic low-energy radioactivity from cosmogenically activated 39Ar, a long-lived (half-life of 269.2y) beta-emitter. With a Q-value of 565 keV, betas from 39Ar decays populate the low-energy ROI for searches of physics beyond the standard model, such as bosonic dark matter. 42Ar (half-life of 32.9y) and its progeny 42K also emit betas that become backgrounds in both the low-energy and 0νββ ROIs. Argon from underground sources has lower activity; specifically, the 39Ar concentration is reduced by a factor of 1400. Monte Carlo simulations show that using radioisotope-depleted argon in the LEGEND-200 experiment would allow the experiment to search for dark matter and other BSM physics. |
Sunday, April 14, 2019 9:18AM - 9:30AM |
G10.00005: Deep level impurity characterization in developing Germanium detectors for detecting rare event physics Sanjay Bhattarai, Dongming Mei, Guoijan Wang, Eric Daniel Lukosi Deep-level impurity impacts germanium detector performance in terms of charge trapping and charge carrier recombination that will eventually broaden energy resolution of germanium detectors. Deep-level impurity characterization in semiconductors is performed widely nowadays using Deep level transient spectroscopy (DLTS) technique. In this technique, the junction is reversed bias and pulse voltage is provided so that the majority charge carrier is in the depletion region. The thermal emission of holes from the deep level in the forbidden gap gives capacitance transient which is measured by the boxcar method. I will talk about the basic DLTS theory, experimental components and different peaks due to the deep level we found in high purity Germanium samples. Using this technique, the deep level traps due to doubly ionized copper and copper-Hydrogen complexes were positively identified. Several unknown traps were also observed. |
Sunday, April 14, 2019 9:30AM - 9:42AM |
G10.00006: Harmonic Oscillator Based Effective Theory and Effective Operators for Neutrinoless Double Beta Decay Kenneth S McElvain Effective theory has been used to connect BSM physics of 0νββ decay to nucleon-level operators. Such nucleon-level operators must be transformed to the effective operators needed in nuclear structure calculations to quantitatively connect decay rates to BSM physics. Transitions of interest, e.g. 76Ge -> 76Se and 130Te -> 130Xe, can be treated in the canonical shell model spaces. As no experimental data exist, a more formal approach to operator renormalization is needed. We implemented HOBET (Harmonic Oscillator Based Effective Theory) operator renormalization Ôeffji=P (Ej/(Ej-HQ)) Ô (Ei/(Ei-QH)) P where indices i and j correspond to eigenstates of the isotopes of interest with P representing a projector for a two-body model space and P+Q=1. The Green's functions with suitable boundary conditions reconstruct the full wave function from the projection. The choice of two-body space will depend on spectator excitation in the A-body wave function. These components enable a calculational path for renormalized operator evaluation. |
Sunday, April 14, 2019 9:42AM - 9:54AM |
G10.00007: First Measurement of gAeff via Low Threshold, High Resolution Spectral Measurements Using In-115 Bolometer Alexander F Leder, Jonathan Ouellet, Fedor Danevich, Pierre de Marcillac, Andrea Giuliani, Joel Kostensalo, Emiliano Olivieri, Claudia Nones, Valentina Novati, Denys Poda, Jouni Suhonen, Vladimir Tretyak, Lindley A Winslow, Anastasiia Zolotarova 0νββ is a nuclear process under investigation by numerous experiments, which if detected would demonstrate that neutrinos are Majorana particles. 0νββ samples a wide range of intermediate forbidden nuclear transitions, which are governed by the quenched axial vector coupling constant (gAeff), the uncertainty of which plays a pivotal role in the uncertainty of the nuclear matrix elements. The recently reexamined role of gAeff in these transitions has prompted measurements of gAeff in highly forbidden decays via beta spectrum shape investigation with high resolution, low threshold bolometers. In this talk, we present measurements performed on a LiInSe2 bolometer, with a 4-fold forbidden beta decay of In-115. This decay is sensitive to similar nuclear effects as 0νββ. We extracted the value of gAeff through the use of a Markov Chain Monte Carlo taking into account experimentally determined background levels. We will discuss the obtained results along with possible impacts this study has for future 0νββ measurements. |
Sunday, April 14, 2019 9:54AM - 10:06AM |
G10.00008: On the difficulty of reconciling Dirac neutrinos with the PMNS matrix. T. Goldman, Gerard J Stephenson If neutrinos are Dirac particles, the universality of the Higgs coupling to the charged fermions of the Standard Model (SM) plus perturbative BSM corrections [1] strongly suggests an approximate congruence between the PMNS matrix and the CKM matrix, which is not observed. We present and discuss the modifications to the Dirac neutrino mass matrix required to remedy the discrepancy.
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