Anatomy of Higgs boson decays into γγ and γZ within the electroweak chiral Lagrangian in the Rξ gauges

摘要

In this work, we study the Higgs boson decays into two photons and into one photon and one Z gauge boson within the context of the nonlinear effective field theory called the electroweak chiral Lagrangian (EChL). We present a detailed computation of the corresponding amplitudes to one-loop level in the covariant R ξ gauges. We assume that the fermionic loop contributions are as in the Standard Model and focus here just in the computation of the bosonic loop contributions. Our renormalization program and the anatomy of the various contributions participating in the R ξ gauges are fully explored. With this present computation, we demonstrate the gauge invariance of the EChL result, not only for the case of on-shell Higgs boson, but also for the most general and interesting case of off-shell Higgs boson. We finally analyze and conclude on the special relevance of the Goldstone boson loops, in good agreement with the expected chiral loops behavior in chiral Lagrangians. We perform a systematic comparison with the corresponding computation of the Standard Model in the R ξ gauges and with the previous EChL results in the unitary gauge. This work represents the first computation within the EChL of these observables to one loop, for both on- and off-shell Higgs boson, in the most general R ξ gauges and with a full renormalization program description, not yet fully explored in the previous literature and which is different to the most frequently used in the linear effective field theory.