ZZ production at nNNLO+PS with MiNNLOPS

Abstract

We consider ZZ production in hadronic collisions and present state-of-the-art predictions in QCD perturbation theory matched to parton showers. Next-to-next-to-leading order corrections to the quark-initiated channel are combined with parton showers using the MiNNLOPS method, while next-to-leading order corrections to the loop-induced gluon fusion channel are matched using the Powheg method. Their combination, dubbed nNNLO+PS, constitutes the best theoretical description of ZZ events to date. Spin correlations, interferences and off-shell effects are included by calculating the full process pp → ℓ+ℓ−ℓ(′)+ℓ(′)−. We show the crucial impact of higher-order corrections for both quark- and gluon-initiated processes as well as the relevance of the parton shower in certain kinematical regimes. Our predictions are in very good agreement with recent LHC data.

Probing Higgs portals with matrix-element based kinematic discriminants in $ZZ \to 4 \ell$ production

“…For the two relevant production channels we calculate the socalled K-factor defined as the ratio between the fiducial cross section at a given order in QCD and the corresponding leading order (LO) QCD prediction. In the case of the gginitiated contribution we utilise the results of [51]. The ratio between the next-to-leading order (NLO) and LO ggF predictions turns out to be essentially flat in m 4 and by averaging we find K NLO gg = 1.83.…”

“…Given the limitations (cf. [51,63,64]) of the state-of-the-art SM predictions of pp → ZZ production for kinematic configurations above the two topquark threshold, achieving the assumed systematic uncertainties of ∆ = 8% and ∆ = 4% is certainly more challenging in the case of the m 4 distribution. The steady progress of perturbative QCD calculations, in particular the exact evaluations of the two-loop on-shell amplitudes for gg → ZZ involving top quarks [65,66] makes us, however, confident that systematic uncertainties in the ballpark of 10% or below are attainable till 3 ab −1 of data are collected at the HL-LHC.…”

Next-to-next-to-leading order event generation for $VH$ production with $H\to b\bar{b}$ decay

“…At first these methods have been applied to the simplest colour singlet processes, namely Higgs-boson production [72,74,78] and Drell Yan [73,79,80]. Especially in the NNLOPS, MiNNLO PS and Geneva approaches a variety of colour-singlet production processes are now available at NNLO+PS, including ZH [81,82], W ± H [82,83], γγ [84], Zγ [85,86], W ± γ [87], ZZ [88,89] and W + W − [90,91] production. Very recently, also the NNLO+PS matching for the very first production process with coloured particles in the initial and final state has been achieved in ref.…”

Top-pair production at the LHC with MiNNLO$_{\rm PS}$

“…The problem of matching NNLO QCD corrections to (leading logarithmic) parton showers (NNLO+PS) has been addressed with different approaches: reweighting of MiNLO generators [5,6], Geneva [7][8][9], Unnlops [10], MiNNLO PS [11,12], and Sector Showers matching [13]. All processes involving only two massless coloured legs (either in the initial or final state) at the Born level can be described with NNLO+PS accuracy by now, and many results have been already obtained [6,[8][9][10][11][12][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. On the other hand, reactions with final-state coloured particles cannot be straightforwardly simulated with the same theoretical accuracy.…”

“…In refs. [11,12,[35][36][37][38][39] the MiNNLO PS formalism was applied to several processes where the system F is a colour singlet. Strictly speaking, eq.…”