arXiv subjects

Daniele Lombardi

Publications and source records attributed to Daniele Lombardi.

14 recordsLinked to original sources

arXiv2026

Resonance-aware parton-shower matching for off-shell top-antitop production with semi-leptonic decays at electron-positron colliders

We present full off-shell NLO corrections in QCD obtained with the MoCaNLO code matched to parton shower. A resonance-aware matching procedure has been devised for the MC@NLO method tuned to the Catani-Seymour dipole subtraction. Specifically, we consider the off-shell production of a top-antitop pair in the semi-leptonic decay channel in electron-positron collisions and match it to the final-state QCD parton shower of PYTHIA8. Distortions of resonances' line shapes are avoided by providing the details of the resonance-cascade chain on an event-by-event basis to the parton shower and by adapting the matching accordingly through the introduction of dedicated counterterms.

hep-ph↗

arXiv2026

The cleanest of them all: NLO electroweak corrections to vector-boson scattering into doubly polarised ZZ pairs at the LHC

We present the first calculation of the next-to-leading-order electroweak corrections to vector-boson scattering into doubly polarised Z bosons at the LHC in the fully leptonic decay channel. The production and decay of the two polarised Z bosons are consistently modelled in the double-pole approximation, separating polarisation states at the amplitude level and including factorisable real and virtual electroweak corrections. Doubly polarised and unpolarised signals are investigated and confronted with off-shell results. A broad analysis, including results at integrated and differential level, is carried out in a realistic, CMS-inspired fiducial setup. Our study paves the way to upcoming analyses with LHC Run-3 and High-Luminosity data as well as to further phenomenological investigations.

hep-ph↗

arXiv2026

NLO QCD and EW corrections to semileptonic vector-boson scattering at the LHC

Vector-boson scattering with semileptonic final states has recently been measured at the LHC, and future experiments are expected to further increase the precision of its measurement, calling for adequate theoretical predictions. In this work, we present a calculation of the NLO QCD and electroweak corrections to the process $\text{p}\text{p} \to \ell^+ ν_\ell + 4\text{j}$ in two different fiducial regions relevant for vector-boson scattering. In a fully off-shell calculation, we provide results for the leading electroweak contribution of $\mathcal{O}\left(α^6\right)$ and the corresponding corrections of $\mathcal{O}\left(α^7\right)$ and $\mathcal{O}\left(α_\text{s} α^6\right)$ for fiducial cross sections and a selection of differential distributions.

hep-ph↗

arXiv2026

Predictions for off-shell $t\bar{t}Z$ production at the LHC: the complete set of LO and NLO contributions

We present predictions for the production and decay of a top--antitop pair in association with a Z boson in the multi-lepton decay channel at the LHC. Our results include the complete set of LO and NLO contributions. Since our calculation is based on full matrix elements, off-shell effects are entirely taken into account. Integrated and differential cross-sections are reported for a realistic fiducial setup.

hep-ph↗

arXiv2025

Electroweak corrections to doubly polarised WZ scattering at the LHC

We present a calculation of next-to-leading-order electroweak corrections to the vector-boson scattering (VBS) process resulting in leptonically decaying W and Z bosons in association with two jets at the LHC. The VBS process is computed for both polarised and unpolarised intermediate bosons, exploiting the pole approximation and the separation of helicity states in tree-level and one-loop amplitudes. A phenomenological analysis is carried out for a realistic fiducial setup at a 13.6 TeV LHC collision energy, highlighting different patterns for the various polarisation states both at integrated and at differential level. This study provides theoretical predictions that are necessary to perform a sound characterisation of the spin structure of VBS processes with full LHC data.

hep-ph↗

arXiv2024

Double-pole approximation for leading-order semi-leptonic vector-boson scattering at the LHC

Measuring vector-boson scattering beyond the fully-leptonic final state is becoming possible at the LHC, which demands to have a solid control on the theory predictions for all final states of this class of processes. In this work we present a full off-shell leading-order calculation for the process $\mathrm{p}\mathrm{p} \to \ell ν_\ell + 4\mathrm{j}$ in two fiducial regions which are particularly relevant for its experimental measurement. In addition to the fully electroweak order, i.e. $\mathcal{O}(α^6)$, we complement our results with $\mathcal{O}(α_\mathrm{s}α^5)$ and $\mathcal{O}(α_\mathrm{s}^2α^4)$ for inclusive predictions. At $\mathcal{O}(α^6)$ we present for the first time a systematic treatment of the process in double-pole approximation and we perform a detailed study of its range of validity by considering inclusive and differential predictions compared to the full off-shell calculation.

hep-ph↗

arXiv2024

NLO corrections to triple vector-boson production in final states with three charged leptons and two jets

Tri-boson production together with vector-boson scattering is a privileged channel to study the electroweak structure of the Standard Model. Upcoming LHC running stages will allow to measure these processes at unprecedented accuracy and for all possible final states, which requires to push theory predictions to still unexplored frontiers. In this work we present the first calculation for the process ${\rm p}{\rm p}\toμ^+μ^-{\rm e}^+ν_{\rm e}\,{\rm j}\,{\rm j}$ at the LHC in a tri-boson phase space. We evaluate the three LO contributions, namely the $\mathcal{O}(α^6)$, which contains the genuine tri-boson signature, along with the $\mathcal{O}(α_{\rm s}α^5)$ and $\mathcal{O}(α_{\rm s}^2α^4)$, and the two $\mathcal{O}(α^7)$ and $\mathcal{O}(α_{\rm s}α^6)$ NLO corrections. The calculation is based on full Standard-Model matrix elements, including all resonant and non-resonant terms, complete spin correlations and interference effects. Integrated and differential cross sections are presented for a fiducial region inspired by High Luminosity LHC prospect studies. We find electroweak corrections of $-14\%$ for the fiducial cross section, almost twice as large as for other tri-boson processes.

hep-ph↗

arXiv2023

Complete NLO corrections to off-shell $\text{t}\overline{\text{t}}\text{Z}$ production at the LHC

Measuring precisely top-pair-associated processes at hadron colliders will become possible with the upcoming LHC running stages. The increased data statistics will especially enable differential measurements leading to an improved characterisation of such processes. Aiming at a consistent data-theory comparison, precise Standard-Model predictions are needed, including higher-order corrections and full off-shell effects. In this work we present NLO-accurate predictions for the production and decay of a top-antitop pair in association with a Z boson at the LHC, in the multi-lepton decay channel. The complete set of LO contributions and NLO corrections of EW and QCD origin is included. The calculation is based on full matrix elements, computed with all resonant and non-resonant contributions, complete spin correlations and interference effects. Integrated and differential cross-sections are presented for a realistic fiducial setup.

hep-ph↗

arXiv2022

$W^\pm Z$ production at NNLO QCD and NLO EW matched to parton showers with MiNNLO$_{\rm PS}$

We consider $W^\pm Z$ production in hadronic collisions and present high-precision predictions in QCD and electroweak (EW) perturbation theory matched to parton showers. To this end, we match next-to-next-to-leading order QCD corrections to parton showers using the MiNNLO$_{\rm PS}$ method and consistently combine them with next-to-leading order EW corrections matched to parton showers. This is the first time such accuracy in the event generation is achieved for any collider process, and we study in detail the impact of different choices in the combination of QCD and EW corrections as well as QCD and QED showers. Spin correlations, interferences and off-shell effects are retained by considering the full leptonic processes $pp \to \ell^+\ell^-\ell'^\pm ν_\ell'$ with $\ell'\neq\ell$ and $\ell'=\ell$ without approximations, and the matching to QED radiation is performed preserving the resonance structure of the process. We find that NNLO QCD predictions including QCD and QED shower effects provide a very good approximation in the bulk-region of the phase space, while EW effects become increasingly important in the high-energy tails of kinematic distributions. Our default predictions are in excellent agreement with recent ATLAS data.

hep-ph↗

arXiv2022

NNLO+PS with MiNNLO$_{\rm PS}$: status and prospects

We summarize the current status and near future prospects for next-to-next-to-leading order calculations matched to parton shower based on the MiNNLO$_{\rm PS}$ method. We give a theoretical overview, illustrate selected results for $ZZ\to 4\ell$ and top-pair production processes at the LHC, and provide an outlook of the future challenges.

hep-ph↗

arXiv2021

Anomalous couplings in $Zγ$ events at NNLO+PS and improving $ν\barνγ$ backgrounds in dark-matter searches

The measurement of the triple gauge couplings (TGCs) is a central part of diboson studies at the LHC. In this letter we consider the $Zγ$ process and include anomalous TGCs (aTGCs) in the event generation at next-to-next-to-leading order QCD accuracy (NNLO+PS) within the MiNNLO$_{\rm PS}$ framework. While our implementation is fully general and applies to both $Z\to \ell^+\ell^-$ and $Z\to ν\barν$ decays, we focus here on the $ν\barνγ$ final state. After validation of our simulation of $ν\barνγ$ events, for which NNLO+PS accuracy is achieved for the first time, the effects of aTGCs on various distributions are studied. Moreover, we show the relevance of NNLO+PS accuracy for the $ν\barνγ$ background to photon plus missing energy signatures in dark-matter searches, and we compare MiNNLO$_{\rm PS}$ predictions for $ν\barνγ$ production to recent 13 TeV data.

hep-ph↗

arXiv2021

$ZZ$ production at nNNLO+PS with MiNNLO$_{\text{PS}}$

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 MiNNLO$_{\text{PS}}$ 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 $pp \to \ell^+\ell^-\ell^{(\prime)+}\ell^{(\prime)-}$. 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.

hep-ph↗

arXiv2021

$W^+W^-$ production at NNLO+PS with MiNNLO$_{\rm PS}$

We consider $W^+W^-$ production in hadronic collisions and present the computation of next-to-next-to-leading order accurate predictions consistently matched to parton showers (NNLO+PS) using the MiNNLO$_{\rm PS}$ method. Spin correlations, interferences and off-shell effects are included by calculating the full process $pp \to e^+ν_e μ^-\barν_μ$. This is the first NNLO+PS calculation for $W^+W^-$ production that does not require an a-posteriori multi-differential reweighting. The evaluation time of the two-loop contribution has been reduced by more than one order of magnitude through a four-dimensional cubic spline interpolation. We find good agreement with the inclusive and fiducial cross sections measured by ATLAS and CMS. Both NNLO corrections and matching to parton showers are important for an accurate simulation of the $W^+W^-$ signal, and their matching provides the best description of fully exclusive $W^+W^-$ events to date.

hep-ph↗

arXiv2020

Advancing MiNNLO$_{\rm PS}$ to diboson processes: $Zγ$ production at NNLO+PS

We consider $Z γ$ 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 $pp\to\ell^+\ell^-γ$. We extend the recently developed MiNNLO$_{\rm PS}$ method to genuine $2\to 2$ hard scattering processes at the LHC, which paves the way for NNLO+PS simulations of all diboson processes. This is the first $2\to2$ 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 $Z γ$ process. Our predictions are in very good agreement with recent ATLAS data.

hep-ph↗