Paper detail

Mass measurements and superallowed beta decay

A recent Penning-trap measurement of the masses of 46V and 46Ti leads to a Qec value that disagrees significantly with the previously accepted value, and destroys overall consistency among the nine most precisely characterized T=1 superallowed beta emitters. This raises the possibility of a systematic discrepancy between Penning-trap measurements and the reaction-based measurements upon which the Qec values depended in the past. We carefully re-analyze (n,gamma) and (p,gamma) reaction measurements in the 24 \leq A \leq 28 mass region, and compare the results to very precise Penning-trap measurements of the stable nuclei 24Mg, 26Mg and 28Si. We thus determine upper limits to possible systematic effects in the reaction results, and go on to establish limits for the mass of radioactive 26Al, to which future on-line Penning-trap measurements can be compared. We stress the urgency of identifying or ruling-out possible systematic effects.