2009 APS April Meeting
Volume 54, Number 4
Saturday–Tuesday, May 2–5, 2009;
Denver, Colorado
Session X2: Neutrino Oscillations in Electron Capture Decays
1:30 PM–3:18 PM,
Tuesday, May 5, 2009
Room: Plaza D
Sponsoring
Unit:
DNP
Chair: Hamish Robertson, University of Washington
Abstract ID: BAPS.2009.APR.X2.2
Abstract: X2.00002 : Searching for Experimental Verification of the Oscillation of Electron Capture Decay Probability
2:06 PM–2:42 PM
Preview Abstract
Abstract
Author:
Paul Vetter
(Lawrence Berkeley National Laboratory)
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.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2009.APR.X2.2