Breakdown of the Isobaric Multiplet Mass Equation as An Effect of the Isospin-Symmetry Breaking
The breakdown of the quadratic form of isobaric multiplet mass equation (IMME), presents a long-standing challenge to the existing theoretical models. In particular, recent high-precision nuclear mass measurements have indicated a dramatic failure of the IMME for several isobaric multiplets. We propose a new mechanism that the isospin-projection $T_z$ dependence of the 1st-order symmetry energy coefficient (SEC) drives a significant breakdown of the IMME, where the 1st-order SEC is primarily induced by the isospin-symmetry breaking (ISB) of strong nuclear force. Completely different from the existing knowledge, the deviation from the IMME cannot be measured simply by the high-order terms such as cubic term $dT_{z}^3$.