Neutrino magnetic moment effects in electron-capture measurements at GSI

Oscillatory behavior of electron capture rates in the two-body decay D→R+ν of hydrogen-like ion into recoil ion plus undetected neutrino ν, with a period of approximately 7 s, was reported in storage ring single-ion experiments at the GSI Laboratory, Darmstadt. Ivanov and Kienle [A.N. Ivanov, P. Kienle, Phys. Rev. Lett. 103 (2009) 062502] have relegated this period to neutrino masses through neutrino mixing in the final state. New arguments are given here against this interpretation, while suggesting that these ‘GSI Oscillations’ may be related to neutrino spin precession in the static magnetic field of the storage ring. This scenario requires a Dirac neutrino magnetic moment μν six times lower than the Borexino solar neutrino upper limit of 0.54×10−10μB [C. Arpesella, et al., Borexino Collaboration, Phys. Rev. Lett. 101 (2008) 091302], and its consequences are briefly explored.