 | (a) Various contributions to $ZH$ production at $\mathcal{O}(\as^3)$: the real-emission contributions from the $qg$ and $q\bar{q}$ channel that include all the diagrams considered in this paper are shown as orange and red lines, respectively. The contributions to the same channels including only the $Z$-radiated diagrams are shown as green ($qg$) and yellow ($q \bar{q}$) lines. The Drell-Yan-like contribution at NNLO is shown as a black line. (b) Comparison of the invariant-mass distribution for $gg\to ZH$ at LO and NLO with the Drell-Yan-like contribution at NNLO. For $gg\to ZH$ at NLO, the results with (blue) and without (orange) the contribution from the $Z$-radiated diagrams are shown. |