quantum beats Flavor mixed massive neutrinos Difference of squared neutrino masses Non-unitarity of flavor mixing matrix CP-violating phases a b s t r a c t
In recent experiments at the GSI, Darmstadt, time-modulated orbital Electron Capture (EC) decays of H-like 140 Pr 58+ , 142 Pm 60+ , and 122 I 52+ ions with one electron in the K-shell, coasting in the ESR storage ring with velocity β = 0.71, were observed. The EC-branches show exponential decay curves time-modulated with period T = 7.06(8) s and amplitude a = 0.18(3) for 140 Pr decays, T = 7.10( ) s and a = 0.23(4) for 142 Pm decays, and T = 6.04(6) s and a = 0.19(3) for 122 I (preliminary) decays in the laboratory frame. The simultaneously measured β + branch of 142 Pm shows no modulation with a < 0.03. We discuss here as origin of the modulation quantum beats produced by the superposition of massive neutrino, mass eigenstates emitted in the entangled two body weak decay. From the modulation frequency a value for the difference of the quadratic mass values m 2 2 -m 2 1 = 2.22(3) × 10 -4 eV 2 is deduced, which is 2.9 times larger than the value derived by the KamLAND antineutrino oscillation experiment. The origin of the small modulation amplitudes is discussed as the result of a partial restoration of the interference terms which are expected to cancel for the usual assumed unitarity of the neutrino flavor mixing matrix.