ZH production in gluon fusion at NLO in QCD

Abstract

We present fully differential next-to-leading order results for Higgs production in association with a Z boson in gluon fusion. Our two-loop virtual contributions are evaluated numerically using sector decomposition, including full top-quark mass effects, and supplemented at high p T by an analytic high-energy expansion to order (m 4 Z , m 4 H , m 32 t ). Using the expanded results we also present a study of the top-quark mass scheme uncertainty at large p T .

On the NLO QCD Corrections to Gluon-Initiated ZH Production

“…For the inclusive cross section, we have found that the NLO QCD corrections are of the same size as the LO contribution, and they increase the cross section by a factor of about 2. Our findings are in accordance with independent results in the literature [28,29]. We have also studied the invariant-mass distribution of the gg → ZH channel at NLO, observing that the perturbative K-factor is not flat across the M ZH range, specifically in the region of threshold ZH production and in the very-high-energy tail (M ZH > 1 TeV).…”

“…[28] (which is in accordance with Ref. [29]) and we have found an agreement at the level of the Monte Carlo error. Furthermore, when we consider the relative importance of the scale uncertainties, we observe very similar results to Ref.…”

“…The former effect has been already observed by the authors of Ref. [29], and our results are in agreement when the same scale choices (µ t = M ZH and µ t = m MS t ) and the same invariant-mass range (M ZH > 400 GeV) are considered. On the other hand, since we can use our analytical results to investigate the low M ZH region, in Fig.…”

“…It should be remarked that our definition of the NLO contribution to gg → ZH process differs from the one employed in Refs. [28,29]. In those references, diagrams in which a Z boson is emitted from an open fermion line, which we denote as Z-radiated diagrams for brevity (see subsection 2.2), were not taken into account because they were assigned to uncalculated N 3 LO corrections to the Drell-Yan-like contribution.…”

“…[28], whereas the very recent calculation of Ref. [29] relies on a combination of the Padé-improved high-energy expansion presented in Ref. [30] and a numerical evaluation using sector decomposition [31].…”