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

TL;DR

This paper presents detailed calculations of NLO electroweak and QCD corrections to Z+gamma production at the LHC, including off-shell effects, photon isolation methods, and anomalous couplings, with results applicable to various energies.

Contribution

It provides the first comprehensive NLO electroweak correction calculations for Z+gamma production including off-shell effects and photon isolation, along with publicly available Monte Carlo tools.

Findings

Electroweak corrections are large at TeV energies, reaching tens of percent.

Photon initial state contributions are moderate or small.

Predictions are provided for multiple LHC energies and differential distributions.

Abstract

The next-to-leading-order electroweak corrections to $pp\to l^+l^-/\bar\nu\nu+\gamma+X$ 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 \'a 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 $ZZ\gamma$ and $Z\gamma\gamma$ couplings.