Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session K12: Low-energy Electroweak Interactions I |
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Sponsoring Units: DNP Chair: Tim Daniels, SLAC Room: Roosevelt 4 |
Sunday, January 29, 2017 1:30PM - 1:42PM |
K12.00001: Neutron Lifetime Measurement Using Magnetically Trapped Ultracold Neutrons Craig Huffer, P.R. Huffman, K.W. Schelhammer, M.S. Dewey, M.G. Huber, P.P. Hughes, H.P. Mumm, A.K. Thompson, K. Coakley, A.T. Yue, C.M. O'Shaughnessy The neutron beta-decay lifetime is important in both nuclear astrophysics and in understanding weak interactions in the framework of the Standard Model. An experiment based at the the NIST Center for Neutron Research was designed to address statistical and systematic limitations of former measurements. In our approach, a beam of 0.89 nm neutrons is incident on a superfluid $^4$He target within the minimum field region of an Ioffe-type magnetic trap. Some of the neutrons are subsequently downscattered by single phonons in the helium to low energies ($<$ 100 neV) and those in the appropriate spin state become trapped. The inverse process, upscattering of UCN, is suppressed by the low phonon density in the $<$ 300 mK helium, allowing the neutron to travel undisturbed through the helium. When the neutron decays the energetic electron produces a scintillation signal in the helium that is detected in real time using photomultiplier tubes. The current measurement is limited by larger than expected systematic corrections. We will discuss the result of the latest dataset and comment on the potential of future measurements. [Preview Abstract] |
Sunday, January 29, 2017 1:42PM - 1:54PM |
K12.00002: Experimental monitoring for the Majorana Demonstrator Wenqin Xu The \textsc{Majorana Demonstrator} neutrinoless double beta (0$\nu\beta\beta$) decay experiment has instrumented two modules of high purity germanium (HPGe) detectors to search for 0$\nu\beta\beta$ decay in $^{76}$Ge. The experiment has started accumulating quality data towards its goal of demonstrating the technical feasibility and low backgrounds for a next generation Ge-based 0$\nu\beta\beta$ experiment. It is critical to extensively monitor the performance of the experimental apparatus without disturbing the blindness data-taking scheme. The experimental monitoring is composed of several stages including, for example, the live monitoring embedded in the Data-Acquisition system, onsite near-live monitoring and data production monitoring. In all stages, automatic alerting mechanisms and scheduled manual checks are implemented in a coordinated way. In this talk, we will discuss the internal management of each experimental monitoring stage and their relationships to each other. [Preview Abstract] |
Sunday, January 29, 2017 1:54PM - 2:06PM |
K12.00003: Charge trapping correction in natural and enriched high-purity Ge detectors for the MAJORANA DEMONSTRATOR Thomas Gilliss A correction for the degradation of pulse height due to trapping of charge carriers in p-type point contact Ge detectors is described. The correction uses approximate time constants characteristic of trapping (and re-emmission) in a detector that lead to exponential decay of charge during drift. As such, the correction can be conveniently implemented during offline analysis in the same manner as a digital pole-zero correction. The MAJORANA DEMONSTRATOR has implemented this correction and a study reveals improvements to energy resolution of detectors. By extending this study to compare the effects of trapping in various experimental configurations of the DEMONSTRATOR, some insight may be gained into the temperature and field dependence of charge trapping in detectors [Preview Abstract] |
Sunday, January 29, 2017 2:06PM - 2:18PM |
K12.00004: Preliminary results of UCN$\tau$ Robert Pattie There is currently a 4$\sigma$ discrepancy between measurements of the neutron lifetime performed using cold neutron beams and those performed with ultracold neutron (UCN) storage vessels. The UCN$\tau$ experiment uses an asymmetric magneto-gravitational UCN trap with {\it in situ} counting of surviving neutrons to measure the neutron lifetime. This design eliminates a major systematic of previous bottle experiments related to the loss of UCN on material trap walls and with unloading neutrons from the storage vessel. A new {\it in situ} detection system was used in the 2015-2016 run that was able to measure the population of surviving UCN at different heights in the trap, providing important information on spectral evolution. Understanding the behavior of quasi-bound UCN in a bottle experiment is essential to achieving a subsecond precision measurement of $\tau_n$. We will present the preliminary results from the 2015-2016 data set and an update on the UCN$\tau$ experiment. [Preview Abstract] |
Sunday, January 29, 2017 2:18PM - 2:30PM |
K12.00005: Neutron-Mirror Neutron Oscillations in a Residual Gas Environment Louis Varriano, Yuri Kamyshkov A precise measurement of the neutron lifetime is important for calculating the rate at which nucleosynthesis occurred after the Big Bang. The history of neutron lifetime measurements has demonstrated impressive continuous improvement in experimental technique and in accuracy. However, two most precise recent measurements performed by different techniques differ by about 3 standard deviations. This difference of 9.2 seconds can possibly be resolved by future experiments, but it may also be evidence of a mirror matter effect present in these experiments. Both mirror matter, a candidate for dark matter, and ordinary matter can have similar properties and self-interactions but will interact only gravitationally with each other, in accordance with observational evidence of dark matter. Three separate experiments have been performed in the last decade to detect the possibility of neutron-mirror neutron oscillations. This work provides a formalism for understanding the interaction of the residual gas in an experiment with ultra-cold neutrons. This residual gas effect was previously considered negligible but can have a significant impact on the probability of neutron-mirror neutron transition. [Preview Abstract] |
Sunday, January 29, 2017 2:30PM - 2:42PM |
K12.00006: An MCMC-based waveform analysis with p-type point contact detectors in the \textsc{Majorana Demonstrator} Benjamin Shanks Statistical signal processing can be a powerful tool for extracting as much information as possible from raw data. By fitting data to a physical model of signal generation on an event-by-event basis, it can be used to perform precise event reconstruction and enable efficient background rejection. Searches for neutrinoless double-beta decay must achieve extremely low backgrounds to reach sensitivities required for discovery, and so can benefit greatly from this analysis technique. The \textsc{Majorana Demonstrator} has implemented a Markov Chain Monte Carlo (MCMC) signal processing algorithm to fit waveforms from p-type point contact (PPC) germanium detectors. After a machine learning step to tune detector fields and electronics response parameters, the MCMC algorithm is able to reconstruct the time, energy and position of interactions within the PPC detector. The parameters estimated with this method will find many applications within the \textsc{Demonstrator} physics program, including background identification and rejection. This will prove important as the \textsc{Demonstrator} aims to reach its background goal of $<3$ counts/tonne/yr in the region of interest. [Preview Abstract] |
Sunday, January 29, 2017 2:42PM - 2:54PM |
K12.00007: Characterization of PPC Detectors for the MAJORANA DEMONSTRATOR Using a Scanning Collimated Source Jamin Rager The \textsc{Majorana Demonstrator} is a $^{76}$Ge double-beta decay experiment located at Sanford Underground Research Facility (SURF) that boasts cutting edge sensitivity and low backgrounds. I report on recent work measuring how charge drift-times vary with respect to the vertical and azimuthal position of physics events within a single-crystal HPGe detector used in the \textsc{Demonstrator}. Understanding these variations will allow for position reconstruction of physics events and identification of the detector's crystal axis, the latter of which will increase the detector's sensitivity to coherently-scattered Primakoff solar axions. Drift-time data was collected with an automated scanning station located at SURF, which used a 133Ba source to create a beam of collimated 81keV gamma-rays. Maximum likelihood analysis was used to fit the data to a set of models for comparison to ongoing work in pulse-shape simulations. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Facility. [Preview Abstract] |
Sunday, January 29, 2017 2:54PM - 3:06PM |
K12.00008: The KATRIN Neutrino Mass Experiment Diana Parno While neutrino oscillation experiments have demonstrated that the particles have non-zero mass, the absolute neutrino mass scale is still unknown. The Karlsruhe Tritium Neutrino experiment (KATRIN) is designed to improve on previous laboratory limits by an order of magnitude, probing the effective neutrino mass with a sensitivity approaching 0.2 eV at 90\% confidence via the kinematics of tritium beta decay. At the same time, KATRIN has the potential to scan for sterile neutrinos at eV and keV scales. After years of preparation, all major components are now on site and commissioning is underway. I will report on the current status of the experiment, including recent results and preparations for the introduction of tritium later this year. [Preview Abstract] |
Sunday, January 29, 2017 3:06PM - 3:18PM |
K12.00009: TRIMS: Validating T$_2$ Molecular Effects for Neutrino Mass Experiments Ying-Ting Lin, Laura Bodine, Sanshiro Enomoto, Matthew Kallander, Eric Machado, Diana Parno, Hamish Robertson The upcoming KATRIN and Project 8 experiments will measure the model-independent effective neutrino mass through the kinematics near the endpoint of tritium beta-decay. A critical systematic, however, is the understanding of the molecular final-state distribution populated by tritium decay. In fact, the current theory incorporated in the KATRIN analysis framework predicts an observable that disagrees with an experimental result from the 1950s. The Tritium Recoil-Ion Mass Spectrometer (TRIMS) experiment will reexamine branching ratio of the molecular tritium (T$_2$) beta decay to the bound state ($^3$HeT$^+$). TRIMS consists of a magnet-guided time-of-flight mass spectrometer with a detector located on each end. By measuring the kinetic energy and time-of-flight difference of the ions and beta particles reaching the detectors, we will be able to distinguish molecular ions from atomic ones and hence derive the ratio in question.We will give an update on simulation software, analysis tools, and the apparatus, including early commissioning results. [Preview Abstract] |
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