Decays of a neutral particle with zero spin and arbitrary CP parity into two off-mass-shell Z bosons

Abstract

We investigate effects of CP symmetry violation in the decay of a scalar particle X (the Higgs boson) into two off-mass-shell Z bosons both decaying into a fermion–antifermion pair, \(X \to {Z_1}*{Z_2}* \to {f_1}{\bar f_1}{f_2}{\bar f_2}\). The most general form of the amplitude of the transition X → Z₁*Z₂*, wherein the boson X may not have definite CP parity, is considered. The applicability limits of the narrow-Z-width approximation used in obtaining differential widths of the decay under consideration are determined. Various observables connected with the structure of the amplitude of the decay X → Z₁*Z₂* are studied. These observables are analyzed in the Standard Model as well as in models conceding indefinite CP parity of the Higgs boson. An experimental measurement of angular and invariant mass distributions of the decay \(X \to {Z_1}*{Z_2}* \to {f_1}{\bar f_1}{f_2}{\bar f_2}\) at the LHC can give information about the CP properties of the Higgs boson and its interaction with the Z boson.