Mass measurements for the Tz=-2 fp -shell nuclei Ti 40, Cr 44, Mn 46, Fe 48, Co 50, and Ni 52

By using isochronous mass spectrometry at the experimental cooler storage ring in Lanzhou, China, masses of short-lived Cr44, Mn46, Fe48, Co50, and Ni52 were measured for the first time and the precision of the mass of Ti40 was improved by a factor of about 2. Relative precisions of δm/m=(1-2)×10-6 have been achieved. Details of the measurements and data analysis are given. The obtained masses are compared with the Atomic-Mass Evaluation 2016 and with theoretical model predictions. The new mass data enable us to extract the higher-order coefficients, d and e, of the quartic form of the isobaric multiplet mass equation for the fp-shell isospin quintets. Unexpectedly large d and e values for the A=44 quintet are found. By revisiting the previous experimental data on β-delayed protons from Cr44 decay, it is suggested that the observed anomaly could be due to the misidentification of the T=2, Jπ=0+ isobaric analog state in V44.