Decay of the higgs boson into a z boson - photon pair in the standard model and beyond.

Abstract

In this work we study the computation of the branching ratio of the Higgs boson decaying into a Z boson-photon pair at leading order. The calculation was performed in detail using the unitary gauge, the obtained results were contrasted with the corresponding expressions in alternative gauge choices. The amplitudes of the dominant contributions, coming from diagrams with a W boson in the loop corrections, were constructed using the path integral formulation and verified with the diagrammatic method of Feynman. The corresponding loop integrals were reduced by using the Passarino-Veltman method. The decay width obtained depends on the square of one of the form factors derived in the tensor reduction. Furthermore, the computation was automated using Wolfram Mathematica in conjunction with the packages FeynArts, FeynCalc, and FeynHelpers, yielding the analytical expression for the decay width. Numerical results obtained using Python yielded a partial decay width at leading order (LO) of 8.33 keV and a corresponding branching ratio of 2.25×10−3. These results indicate a discrepancy of 1.15×10−3 when compared to the experimental branching ratio, (3.4 ± 1.1) × 10−3, for a Higgs boson mass of 125 GeV.