Test of IMME in fp shell via direct mass measurements of TZ = −3/2 nuclides, Y. H. Zhang, Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou, China − The isobaric multiplet mass equation (IMME) is the most basic prediction to follow from the concept of isospin in nuclear physics, and the test of IMME is clearly of fundamental importance for which precise binding energies of at least four TZ ³ 3/2 members are needed.  In a recently commisioned cooler storage ring CSRe in Lanzhou, atomic masses of eight TZ = −3/2 isotopes 41Ti, 43V, 45Cr, 47Mn, 49Fe, 51Co, 53Ni, and 55Cu have been measured using the isochronous mass spectroscopy, providing mass data for testing the validity of IMME in the fp shell. In this talk, experimental details and data analysis method are described and atomic masses of the above-mentioned TZ = −3/2 isotopes are reported.  We have fitted the mass data of four isobars of A = 41, 45, 49, and 53, respectively, using a cubic expression by inclusion of a d×TZ3 term.  The d coefficients are consistent with zero within error bars for the A= 41, 45, and 49 isobars.  However the d coefficient for the A=53 isobar is more than 3σ deviated from zero, giving a signature of breakdown of the isobaric multiplet mass equation at A=53, T=3/2.  This result calls for more precise determinations (in the order of keV) of ground-state mass of 53Ni and excitation energy of the isobaric analog state in 53Co.