Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session R12: Low-energy Electroweak Interactions II |
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Sponsoring Units: DNP Chair: Diana Parno, Carnegie Mellon University Room: Roosevelt 4 |
Monday, January 30, 2017 10:45AM - 10:57AM |
R12.00001: Precision measurement of the positron asymmetry of laser-cooled, spin-polarized \textsuperscript{37}K Dan Melconian, B. Fenker, J.A. Behr, M. Anholm, D. Ashery, R.S. Behling, I. Cohen, I. Craiciu, A. Gorelov, G. Gwinner, J. McNeil, M. Mehlman, S. Smale, C.L. Warner Precision low-energy measurements in nuclear $\beta$ decay can be used to provide constraints on possible physics beyond the standard model, complementing searches at high-energy colliders. The short-lived isotope \textsuperscript{37}K was produced at ISAC-TRIUMF and confined in an alternating magneto-optical trap before being spin-polarized to 99.13(9)\% via optical pumping. Our system allows for an exceptionally open geometry with the decay products escaping with their momenta unperturbed by the shallow trapping potential. The emitted positrons are detected in a pair of symmetric detectors placed along the polarization axis to measure the $\beta$ asymmetry. The analysis was performed blind and considers $\beta$-scattering as well as other systematic effects. The results place limits on the mass of a hypothetical $W$ boson coupling to right-handed neutrinos as well as contribute to an independent determination of the $V_{ud}$ element of the CKM matrix. The $\beta$ asymmetry result as well as improvements and future plans will be described. [Preview Abstract] |
Monday, January 30, 2017 10:57AM - 11:09AM |
R12.00002: Time reversal violation in radiative beta decay: experimental plans J.A. Behr, J. McNeil, M. Anholm, A. Gorelov, D. Melconian, D. Ashery Some explanations for the excess of matter over antimatter in the universe involve sources of time reversal violation (TRV) in addition to the one known in the standard model of particle physics. We plan to search for TRV in a correlation between the momenta of the beta, neutrino, and the radiative gamma sometimes emitted in nuclear beta decay. Correlations involving three (out of four) momenta are sensitive at lowest order to different TRV physics than observables involving spin, such as electric dipole moments and spin-polarized beta decay correlations. Such experiments have been done in radiative kaon decay, but not in systems involving the lightest generation of quarks. An explicit low-energy physics model being tested [Gardner and He, Phys. Rev. D 87 116012 (2013)] produces TRV effects in the Fermi beta decay of the neutron, tritium, or some positron-decaying isotopes. We will present plans to measure the TRV asymmetry in radiative beta decay of laser-trapped $^{38m}$K at better than 0.01 sensitivity, including suppression of background from positron annihilation. [Preview Abstract] |
Monday, January 30, 2017 11:09AM - 11:21AM |
R12.00003: Result from, and status of, EXO-200 Tim Daniels EXO-200 has provided one of the most sensitive searches for neutrinoless double-beta decay utilizing 175\,kg of enriched liquid xenon in an ultra-low background time projection chamber. This detector has demonstrated excellent energy resolution and background rejection capabilities. Using the first two years of data, EXO-200 has set a limit of $1.1\times10^{25}$y at 90% C.L. on the neutrinoless double-beta decay half-life of $^{136}$Xe. The experiment has experienced a brief hiatus in data taking during a temporary shutdown of its host facility: the Waste Isolation Pilot Plant. EXO-200 has resumed data taking in earnest with upgraded detector electronics. Results from the analysis of EXO-200 data and an update on the current status of EXO-200 will be presented. [Preview Abstract] |
Monday, January 30, 2017 11:21AM - 11:33AM |
R12.00004: Progress towards barium daughter tagging in $Xe^{136}$ decay using single molecule fluorescence imaging Austin Mcdonald, Ben Jones, Jordan Benson, David Nygren The existence of Majorana Fermions has been predicted, and is of great interest as it may be related to the asymmetry between matter and anti-matter particles in the universe. However, the search for them has proven to be a difficult one. Neutrino-less Double Beta decay (NLDB) offers a possible opportunity for direct observation of a Majorana Fermion. The rate for NLDB decay may be as low as $\approx 1 $ $count/ton/year$. Current detector technologies have background rates between $4$ to $ 300$ $count/ton/year/ROI$ which is much larger than the universal goal of $0.1$ $count/ton/year/ROI$ desired for ton-scale detectors. The premise of my research is to develop new detector technologies that will allow for a background-free experiment. My current work is to develop a sensor that will tag the daughter ion $ Ba^{++}$ from the $Xe^{136}$ decay. The development of a sensor that is sensitive to single barium ion detection based on the single molecule fluorescence imaging technique is the major focus of this work. If successful, this could provide a path to a background-free experiment. [Preview Abstract] |
Monday, January 30, 2017 11:33AM - 11:45AM |
R12.00005: ABSTRACT WITHDRAWN |
Monday, January 30, 2017 11:45AM - 11:57AM |
R12.00006: Sensitivity of the LUX detector to the possible neutrinoless double beta decay of $^{134}$Xe Evan Pease The Large Underground Xenon (LUX) detector is a 370-kg liquid xenon (LXe) time-projection chamber designed primarily for the direct detection of weakly-interacting massive particles (WIMPs), a leading dark matter candidate. LUX operates on the 4850-foot level of the Sanford Underground Research Facility in Lead, SD. The unenriched xenon of LUX contains the natural 10.4\% abundance of the isotope $^{134}$Xe, a candidate for the lepton-number-violating process of neutrinoless double beta (0$\nu\beta\beta$) decay. If observed, this process would confirm the existence of massive Majorana neutrinos and would be a possible path to the measurement of neutrino mass and other studies of new weak-interaction physics. Given its xenon mass and the length of exposure for the LUX detector, there is an opportunity to improve upon the $T_{1/2} > 5.8 \times 10^{22}$ yr sensitivity of the 6.5-kg DAMA experiment (enriched to 17.1\% $^{134}$Xe) from 2002 (Bernabei, et al., Phys. Lett. B 527, 182-186, 2002.). Building upon previous LUX measurements of the energy resolution and signal yields up to 662~keV, this talk will go over the response of the LUX detector at 826 keV, the $^{134}$Xe $Q$-value, and the current status of the LUX $^{134}$Xe 0$\nu\beta\beta$ analysis. [Preview Abstract] |
Monday, January 30, 2017 11:57AM - 12:09PM |
R12.00007: A New Strangeness Fit to World Parity-Violating Electron Scattering Data Benjamin Gilbert A global experimental effort to determine the strangeness content of nuclei, including experiments such as G0, SAMPLE, HAPPEx, and A4, have presented results on the precision frontier for parity-violating electron scattering. In particular, the kinematics of these experiments are in the low momentum-transfer region ($Q^2 $ \textless \hspace{1mm} 1), to allow more robust extrapolation to the static ($Q^2$ = 0) properties of the nucleon. The combination of these results into a global fit presents a new opportunity to comment on the globally observed strangeness content in nuclei. The process for constructing this fit faces certain challenges, with electromagnetic form factor model dependence standing out in particular. A novel fit including the most recent data for $^1$H, $^2$H, and $^4$He target parity-violating electron scattering experiments will also be presented, suggesting small but non-zero electromagnetic strangeness contributions. [Preview Abstract] |
Monday, January 30, 2017 12:09PM - 12:21PM |
R12.00008: Project 8: Towards cyclotron radiation emission spectroscopy on tritium Martin Fertl Project 8 aims to determine the neutrino mass by making a precise measurement of the beta decay of molecular tritium (Q = 18.6 keV) using the recently demonstrated the technique of cyclotron radiation emission spectroscopy (CRES). We report on results for calibration measurements performed with Kr-83m in a gas cell that fulfills the stringent requirements for a measurement using tritium: cryogenic operation, safe tritium handling, a non-magnetic design, and a good microwave guide performance. The phased program that allows Project 8 to probe the neutrino mass range accessible using molecular tritium is described. [Preview Abstract] |
Monday, January 30, 2017 12:21PM - 12:33PM |
R12.00009: Project 8 Phase II: Improved beta decay electrons reconstruction Mathieu Guigue The Project 8 collaboration aims to measure the absolute neutrino mass scale using a cyclotron radiation emission spectroscopy technique on the beta decays of tritium. The second phase of the project will measure a differential spectrum of tritium beta decays and extract the tritium endpoint value with an eV or sub-eV scale precision. Monoenergetic electrons emitted by gaseous $^{83\mathrm{m}}$Kr atoms can be used to determine the coefficient between the cyclotron frequency and the electron energy and to optimize the instrument configuration for the tritium measurement. We present the progress on the processing of the electron cyclotron radiation signal to reconstruct the beta decay spectrum of krypton and tritium. [Preview Abstract] |
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