NLO QCD and electroweak corrections to $Z+γ$ production with leptonic Z-boson decays

TL;DR

This work delivers a complete NLO electroweak treatment of $pp\to ZZ\gamma$ with leptonic $Z$ decays, including off-shell effects through the complex-mass scheme and initial-state photons, and it reproduces known NLO QCD results. It incorporates photon separation through both a quark-to-photon fragmentation function and Frixione cone isolation, and provides Monte Carlo tools for arbitrary differential cross sections. The analysis covers integrated cross sections at 7, 8, and 14 TeV and differential distributions at 14 TeV for bare muons and dressed leptons, while also examining the impact of anomalous $ZZZ\gamma$ and $ZZ\gamma\gamma$ couplings. Overall, the paper advances precision background predictions for high-energy collider phenomenology and enables robust studies of potential new-physics effects in $Z Z+\gamma$ final states.

Abstract

The next-to-leading-order electroweak corrections to $pp\to l^+l^-/\barνν+γ+X$ production, including all off-shell effects of intermediate Z bosons in the complex-mass scheme, are calculated for LHC energies, revealing the typically expected large corrections of tens of percent in the TeV range. Contributions from quark-photon and photon-photon initial states are taken into account as well, but their impact is found to be moderate or small. Moreover, the known next-to-leading-order QCD corrections are reproduced. In order to separate hard photons from jets, both a quark-to-photon fragmentation function á la Glover/Morgan and Frixione's cone isolation are employed. The calculation is available in the form of Monte Carlo programs allowing for the evaluation of arbitrary differential cross sections. Predictions for integrated cross sections are presented for the LHC at 7 TeV, 8 TeV, and 14 TeV, and differential distributions are discussed at 14 TeV for bare muons and dressed leptons. Finally, we consider the impact of anomalous $ZZγ$ and $Zγγ$ couplings.

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