Gauge- and Renormalization-Group- Invariant Formulation of the Higgs-Boson Resonance

A gauge- and renormalization-group- invariant approach implemented by the pinch technique is formulated for resonant transitions involving the Higgs boson. The lineshape of the Higgs boson is shown to consist of two distinct and physically meaningful contributions: a process-independent resonant part and a process-dependent non-resonant background, which are separately gauge independent, invariant under the renormalization group, satisfy naive, tree-level Ward identities, and respect the optical and equivalence theorem individually. The former process-independent quantity serves as the natural extension of the concept of the effective charge to the case of the Higgs scalar, and constitutes a common ingredient of every Born-improved amplitude. The difference in the phenomenological predictions obtained within our approach and those found with other methods is briefly discussed.