Advancing MıNNLOPS to diboson processes: Zγ production at NNLO+PS

Abstract

We consider Zγ production in hadronic collisions and present the first computation of next-to-next-to-leading order accurate predictions consistently matched to parton showers (NNLO+PS). Spin correlations, interferences and off-shell effects are included by calculating the full process pp → ℓ+ℓ−γ. We extend the recently developed MiNNLOPS method to genuine 2 → 2 hard scattering processes at the LHC, which paves the way for NNLO+PS simulations of all diboson processes. This is the first 2 → 2 NNLO+PS calculation that does not require an a-posteriori multi-differential reweighting. We find that both NNLO corrections and matching to parton showers are crucial for an accurate simulation of the Zγ process. Our predictions are in very good agreement with recent ATLAS data.

W+W− production at NNLO+PS with MINNLOPS

“…[76], and generalized to 2 → 2 colour-singlet scattering processes in ref. [92]. In the following we recall the basic ideas and essential ingredients of MiNNLO PS , adapting the notation of refs.…”

“…In the following we recall the basic ideas and essential ingredients of MiNNLO PS , adapting the notation of refs. [75,76,92].…”

“…Most NNLO+PS applications have been done for simple 2 → 1 LHC processes or 1 → 2 decays so far, such as Higgs-boson production [75,76,80,81], Drell-Yan (DY) production [74][75][76][82][83][84], Higgsstrahlung [85][86][87], which is still a 2 → 1 process with respect to QCD corrections, and the H → b b decay [88][89][90]. There are a few notable exceptions where NNLO+PS matching was achieved for more involved colour-singlet processes, namely W + W − [91], Zγ [92], γγ [93] and ZZ [94] production. Moreover, with top-quark pair production the very first NNLO+PS calculation for a coloured initial and final state has been presented in ref.…”

“…MiNNLO PS method [75,76] and its extension to 2 → 2 reactions presented in ref. [92]. At variance with the NNLOPS calculation of ref.…”

Matching N3LO QCD calculations to parton showers

“…Fully-differential matching procedures are presently only available in NLO QCD, since the (fully differential) singularity-structure of QCD is not yet captured by any available parton shower. This has however not prevented several successful combinations of NNLO predictions and event generators [31,[34][35][36][37][38][39][40][41][42][43][44][45][46]. Phase-space slicing inspired unitarized merging methods offer a convenient stepping stone towards high accuracy.…”