Bulletin of the American Physical Society
2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009; Denver, Colorado
Session X2: Neutrino Oscillations in Electron Capture Decays |
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Sponsoring Units: DNP Chair: Hamish Robertson, University of Washington Room: Plaza D |
Tuesday, May 5, 2009 1:30PM - 2:06PM |
X2.00001: Non-exponential orbital electron capture decay of Hydrogen-like Ions Invited Speaker: In this talk we report on the observation of time-modulated orbital electron-capture decays of hydrogen-like $^{140}$Pr$^{58+}$ and $^{142}$Pm$^{60+}$ ions coasting in the ion storage-cooler ring ESR at GSI. By using non-destructive, time-resolved Schottky mass spectrometry of single ions it turned out that the expected exponential decay is periodically modulated in time with an oscillation period of about 7 seconds for both systems. By our special detection technique most of systematic errors, such as time-modulated detection efficiencies, can be excluded - at the expense of restricted counting statistics, however. The interpretation of the observed effect is broadly disputed in literature. Some scenarios show that our observations can be attributed to the coherent creation of finite mass eigenstates of the electron neutrino in these two- body weak decays. Electron capture decay of hydrogen-like $^{122}$I$^{52+}$ has been studied very recently to investigate a possible scaling of the modulation frequency with the mass of the recoiling daughter nucleus. The data analysis is still in progress. The experiment, the preliminary results, and future plans will be discussed. [Preview Abstract] |
Tuesday, May 5, 2009 2:06PM - 2:42PM |
X2.00002: Searching for Experimental Verification of the Oscillation of Electron Capture Decay Probability Invited Speaker: A group from Gesellschaft f\"{u}r Schwerionenforschung (GSI) last year published an observation of time oscillations of the electron capture decay rate of stored hydrogen-like ions of $^{142}$Pm and $^{140}$Pr.(Phys.~Lett.~B {\bf 664}, 162 (2008)). They proposed that the oscillating decay rate was caused by interference between momentum states of the ion caused by neutrino mass and flavor mixing. This hypothesis has been controversial, with several authors arguing either that neutrino mixing can or cannot be responsible. If neutrino mixing is responsible for the decay rate oscillations, then it should be possible to detect these oscillations in a simpler experiment without using stored hydrogenic ions, by observing an electron capture decay rate with an appropriate experiment time structure. If this were possible, it could revolutionize the study of neutrino mixing by allowing much simpler experiments to make precise measurements of mass differences and mixing angles. At LBNL, we performed an experiment to search for oscillations in electron capture rate using $^{142}$Pm produced with a time short compared to the oscillation period, and counting $^{142}$Nd K$_{\alpha}$ x-rays from the daughter. The decay time spectrum is well-described by a simple exponential, and we observed no statistically significant decay rate oscillations at a level much lower than proposed. A literature search for previous experiments that might have been sensitive to the reported modulation uncovered a candidate in $^{142}$Eu. A reanalysis of that published data shows no decay rate oscillation. A recent experiment at Munich also did not observe decay rate oscillations in decays of $^{180}$Re. Other potential explanations for the GSI decay oscillation data have been proposed, including quantum beats by nearly degenerate initial parent ion states and Thomas precession in the stored ions. I will discuss the status of experimental results, and possibilities for experimental confirmation of the various models. This work was supported by the Director, Office of Science, Office of Nuclear Physics, U.S. Department of Energy under Contract No. DE-AC02-05CH11231. [Preview Abstract] |
Tuesday, May 5, 2009 2:42PM - 3:18PM |
X2.00003: Theoretical Understanding of the GSI Anomaly Invited Speaker: |
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