Current quark-mass dependence of nucleon magnetic moments and radii

A calculation of the current quark-mass dependence of nucleon static electromagnetic properties is necessary in order to use observational data as a means to place constraints on the variation of Nature's fundamental parameters. A Poincare-covariant Faddeev equation, which describes baryons as composites of confined quarks and nonpointlike diquarks, is used to calculate this dependence. The results indicate that, like observables dependent on the nucleons' magnetic moments, quantities sensitive to their magnetic and charge radii, such as the energy levels and transition frequencies in hydrogen and deuterium, might also provide a tool with which to place limits on the allowed variation in Nature's constants.