  The discovery of the Higgs boson, with mass known to better than the percent
level, enables for the first time precision Higgs boson analyses. Toward this
goal, we define an expansion formalism of the Higgs boson partial widths and
branching fractions that facilitates such studies. This expansion yields the
observables as a perturbative expansion around reference values of Standard
Model input observables (quark masses, QCD coupling constant, etc.). We compute
the coefficients of the expansion using state-of-the-art results. We also study
the various sources of uncertainties in computing the partial widths and
branching fractions more precisely. We discuss the impact of these results with
efforts to discern new physics through precision Higgs boson studies.
