First direct determination of the 48Ca double-β decay Q value.

The low-energy beam and ion trap Penning trap mass spectrometer was used for an improved determination of the 48Ca double-β decay Q value: Qββ -- 4268.121 (79) keV. The new value is 1.2 keV greater than the value in the 2012 atomic mass evaluation [Chin. Phys. C 36, 1603 (2012)], a shift of three a, and is a factor of 5 more precise. Accurate knowledge of this Q value is important for experimental searches to observe neutrinoless double-β) decay (0vββ) in 48Ca and is essential for extracting the effective mass of the electron neutrino if the 48Ca half-life of Ovfifi was experimentally determined. [ABSTRACT FROM AUTHOR]