Fingerprinting the contribution of colored scalars to the $H^+ W^- Z(\gamma)$ vertex

Color-octet scalars arise in various Grand Unification scenarios and also in other models of new physics. They are also postulated for minimal flavour violation. Purely phenomenological imprints of such scalars are therefore worth looking at. Motivated by this, we perform a complete one-loop calculation of the $H^+ \to W^+ Z (\g)$ decay in a two Higgs doublet model augmented by a color-octet $SU(2)_L$ scalar doublet. The computation is conveniently segregated into colorless and colored components. The color-octet part of the amplitude, being scaled by the color-factor, provides an overall enhancement to the form factors. Crucial constraints from perturbative unitarity, positivity of the scalar potential, oblique parameters, Higgs signal strengths and direct search of a charged Higgs and color-octet scalars are folded-in into the analysis. Sensitivity of the loop-induced $H^+ \to W^+ Z (\g)$ vertex to other model parameters is elucidated. Finally, the prospect of observing a loop-induced $H^+ \to W^+ Z (\g)$ interaction at the future hadronic collisions is also discussed.
Comment: 27 pages (in 2 column format), 4 tables, 15 captioned figures. Version published in EPJC