Why the fermion dynamical symmetry model fails to predict nuclear masses: A comprehensive assessment - art. no. 014308

In the last several years new experimental data have become available on al pha-decay chains starting in the predicted deformed superheavy region near (272)110. This has: promoted new interest in nuclear mass formulas and how well they extrapolate to regions far beyond where experimental masses were previously known. We here focus on two such mass models, namely the fermion dynamical symmetry model and the finite-range droplet model. We have chose n these models since they both reproduce previously known actinide masses w ith good accuracy, but rapidly diverge from each other in the region of the recently observed new elements. Furthermore, the two models have been the subject of animated discussions concerning which one gives the most reliabl e predictions of nuclear masses in the superheavy region and in the termina ting region of the r process. The new data support the predictions of the f inite-range droplet model. We discuss the fermion dynamical symmetry model and its application [Han ct al., Phys. Rev. C 45, 1127 (1992)] to the calcu lation of trans-Pb nuclear masses. As will be shown, the model contains unp hysical features and has many more free constants than claimed. The values obtained for the constants and the model agreement with data in the legion of adjustment are therefore of no particular significance and severe diverg ences occur for recently discovered nuclei outside the region of adjustment .