Speaker
Description
Shell model calculations rely on effective Hamiltonians to convey observables. While the results from different Hamiltonians are generally consistent, residual uncertainties leave predictions open to question. To address this, we apply advanced statistical techniques to assign meaningful error bars to both known observables and those yet to be measured. Two unmeasured observables are of particular interest: the neutrinoless double-beta decay rate and the absolute neutrino mass. Both have motivated extensive experimental and theoretical efforts. Observing this decay would establish that neutrinos are Majorana particles (i.e., their own antiparticles), confirm that neutrino mass is nonzero, and require exploring beyond-Standard-Model mechanisms for generating that mass. Our recent work tackles this problem in steps. First, we compute observables relevant to this decay for both the parent and daughter nuclear structures. We then compare our results against experimental data and use them to predict neutrinoless nuclear matrix elements. Starting from several well-established effective Hamiltonians, we introduce small perturbations to their matrix elements while preserving the magicity of the core. Hundreds of perturbed Hamiltonians generate statistical distributions for the observables and predictions, yielding standard deviations and quantified theoretical uncertainties. Finally, we examine the correlations between the calculated observables.