arXiv subjects

Giovanni Pelliccioli

Publications and source records attributed to Giovanni Pelliccioli.

At least 19 recordsLinked to original sources

arXiv2026

Limitations of quantum tomography in Higgs-boson decays to four leptons

We investigate the limitations of the two-qutrit quantum tomography in Higgs-boson decays to four charged leptons. At next-to-leading order, the standard reconstruction can yield an operator that is not positive semidefinite, even when radiatively improved spin-analysing powers are used. We trace this failure to the coherent combination of photon- and Z-mediated contributions to the off-shell dilepton system, whose distinct production and decay structures invalidate the assumed universal decay analysers. Nevertheless, the rank-two angular sector remains accessible and perturbatively stable, enabling a robust lower bound on the squared concurrence, and hence a reliable assessment of entanglement beyond leading order.

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arXiv2026

Top-Antitop Production and Decay at Threshold at the LHC in QCD Perturbation Theory

In this work we consider the production of a top-antitop pair at the LHC when the mass of the pair is relatively near to the nominal threshold, that is to say to twice the top pole mass. In this regime, enhanced perturbative corrections arise that can be computed to all orders in perturbation theory. We present three generators of the NLO+PS kind (Next-to-Leading-Order that can be interfaced to parton showers) that include these threshold enhanced effects. Using these generators we address the following questions: what is the size of enhanced non-relativistic effects that are not already present in the well known NLO and NNLO perturbative results; what is the size of the contribution from these effects that can be loosely attributed to toponium production; and to what extent the finite width of the top quark affects threshold enhanced corrections. Our generators are relevant for the recent observation of enhanced $t{\bar t}$ production near threshold in the pseudoscalar channel by the ATLAS and CMS collaborations.

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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.

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arXiv2026

Higher-order effects in amplitude-assisted polarisation extraction with machine-learning techniques

With increasing experimental precision, the prospect of extracting the polarisation of electroweak gauge bosons is becoming particularly attractive. To this end, regression and classification procedures based on precise and accurate theoretical predictions are becoming increasingly important. In this work, we present the first amplitude-assisted regression procedure at next-to-leading-order accuracy in QCD, supplemented with parton-shower effects, using machine-learning techniques to extract the rate of longitudinal-boson production in high-energy collisions. Several neural-network architectures are presented and benchmarked against a standard random-forest regressor, demonstrating the robustness of the results for di-boson production at the LHC.

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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.

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arXiv2026

Polarized-boson pairs at NLO in the SMEFT

We present a computation of diboson production in the $W^\pm Z$ channel at the Large Hadron Collider (LHC), incorporating leptonic decays of the gauge bosons and considering intermediate gauge bosons with definite polarization states. The analysis includes contributions from the Standard Model effective field theory (SMEFT) and is carried out at next-to-leading order accuracy in QCD, matched to a parton-shower simulation. Our implementation allows for the selection of specific helicity configurations, both in the Standard Model and in the presence of dimension-six operators inducing anomalous triple-gauge-boson couplings. This work provides a key ingredient for both polarization-template and quantum-tomography analyses of diboson systems at the LHC within the SMEFT framework.

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arXiv2026

Triple-gauge couplings in LHC diboson production: a SMEFT view from every angle

This study explores fully leptonic WZ and WW production at the LHC within the SMEFT framework at NLO in QCD, focusing on both CP-even and CP-odd triple-gauge-coupling dimension-six operators. We investigate the off-shell processes, contrasting our findings in inclusive setups with those in the presence of realistic fiducial selections. Alongside the conventional kinematic observables, we examine polarisation-sensitive observables and angular coefficients. Moreover, we assess potential SMEFT effects on asymmetry observables. Through a sensitivity analysis, we identify critical LHC observables that are particularly sensitive to SMEFT-induced modifications, thereby shedding light on potential avenues for new-physics searches in diboson production at the LHC.

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arXiv2026

SMEFT effects on spin correlations and entanglement at NLO QCD in di-boson production at hadron colliders

We perform for the first time a full study of spin correlations in inclusive WZ production at the LHC with leptonic decays in the presence of NLO QCD corrections and of effects from a dimension-six operator in the SMEFT modifying the electroweak triple-gauge coupling. We carry out the complete quantum-state tomography of the di-boson system and relate its results to common purity and spin-entanglement markers, highlighting the sizeable impact of both QCD corrections and SMEFT insertions. Additionally, we show how a naive truncation at dimension-six in the SMEFT expansion of the spin-density matrix can lead to a cumbersome spin interpretation of the quantum-tomography results.

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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.

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arXiv2025

Precise predictions for joint polarisation fractions in WZ production at the LHC

We achieve for the first time NNLO QCD + NLO EW accuracy for doubly polarised WZ inclusive production at the LHC, in the case of fully leptonic decays. Additionally, we provide estimates for missing higher-order uncertainties in QCD associated with doubly polarised differential cross sections and joint polarisation fractions, obtained both with standard scale variations and with a theory-nuisance-parameter approach. The study is carried out in the fiducial setup of a recent ATLAS analysis of Run-2 data.

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arXiv2025

Quantum Information meets High-Energy Physics: Input to the update of the European Strategy for Particle Physics

Some of the most astonishing and prominent properties of Quantum Mechanics, such as entanglement and Bell nonlocality, have only been studied extensively in dedicated low-energy laboratory setups. The feasibility of these studies in the high-energy regime explored by particle colliders was only recently shown and has gathered the attention of the scientific community. For the range of particles and fundamental interactions involved, particle colliders provide a novel environment where quantum information theory can be probed, with energies exceeding by about 12 orders of magnitude those employed in dedicated laboratory setups. Furthermore, collider detectors have inherent advantages in performing certain quantum information measurements, and allow for the reconstruction of the state of the system under consideration via quantum state tomography. Here, we elaborate on the potential, challenges, and goals of this innovative and rapidly evolving line of research and discuss its expected impact on both quantum information theory and high-energy physics.

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arXiv2025

Z-boson quantum tomography at next-to-leading order

We investigate the origin of the unusually large electroweak (EW) radiative effects observed in the extraction of the spin-density matrix and related observables at colliders, focusing on leptonic Z-boson decays. We compute the Z-boson-decay spin-density matrix at next-to-leading order (NLO) and find that, while its analytic structure remains essentially unchanged with respect to leading order, the EW corrections induce a sizeable $-35\%$ shift in the spin-analysing-power parameter $η_\ell$. This effect alone accounts for the striking size of the corrections. For boosted Z bosons, we further show that the treatment of photon radiation in lepton-dressing algorithms significantly affects the extraction of spin-density-matrix coefficients at NLO and must be carefully controlled. To address these challenges, we propose a quantum tomography procedure that is applicable to any final state with one or more on-shell Z bosons that is robust under higher-order corrections. We illustrate its validity and limitations in ${\textrm{pp}} \to {\textrm{ZZ}} \to 4\ell$ and in heavy ($M_{\textrm{H}}>2 M_{\textrm{Z}}$) Higgs-boson decay ${\textrm{H}}\to {\textrm{ZZ}} \to 4\ell$.

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arXiv2025

Precise Standard-Model predictions for polarised Z-boson pair production and decay at the LHC

Providing accurate theoretical predictions in the Standard Model for processes with polarised electroweak bosons is crucial to understand more in-depth the electroweak-symmetry breaking mechanism and to enhance the sensitivity to potential new-physics effects. Motivated by the rapidly increasing number of polarisation analyses of di-boson processes with LHC data, we carry out a comprehensive study of the inclusive production of two polarised Z bosons in the decay channel with four charged leptons. We perform a detailed comparison of fixed-order predictions obtained with various Monte Carlo programs which rely on different signal-definition strategies, assessing non-resonant and interference effects by contrasting polarised results with unpolarised and full off-shell ones. For the first time, we accomplish the combination of NNLO QCD and NLO EW corrections, setting the new state-of-the-art perturbative accuracy for polarised Z-boson pairs at the LHC. The impact of parton-shower matching and multi-jet merging is investigated by scrutinising calculations obtained with event generators that are typically used in experimental analyses. Integrated and differential results are discussed in a realistic fiducial setup and compared to publicly available ATLAS results.

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arXiv2024

NLO EW and QCD corrections to polarised same-sign WW scattering at the LHC

We present the first calculation of same-sign WW scattering at the LHC in the fully leptonic decay channel including the modelling of polarisation for intermediate electroweak bosons and radiative corrections up to NLO EW+QCD accuracy. The predictions rely on a pole expansion and on the split of polarisation states at matrix-element level. Doubly-polarised and unpolarised signals are investigated together with full off-shell results. A detailed phenomenlogical analysis is carried out focusing on differential observables that discriminate between polarisation states, paving the way for refined polarisation-oriented analyses of vector-boson scattering with Run-3 LHC data.

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arXiv2024

From angular coefficients to quantum observables: a phenomenological appraisal in di-boson systems

Motivated by the growing interest in accessing the spin structure of multi-boson processes and in measuring quantum entanglement at high energies, we study polarisation and spin-correlation coefficients in di-boson systems. We show that higher-order corrections of QCD and electroweak type, off-shell modelling, and realistic effects such as fiducial selections and neutrino reconstruction are unavoidable to properly determine such coefficients, and consequently to provide a sound interpretation of observables sensitive to quantum entanglement and Bell-inequality violation. Our findings are based on a detailed phenomenological analysis of boson pairs at the LHC, either in inclusive electroweak production or coming from Higgs-boson decays.

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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.

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arXiv2024

NNLO subtraction for any massless final state: a complete analytic expression

We use the Local Analytic Sector Subtraction scheme to construct a completely analytic set of expressions implementing a fully local infrared subtraction at NNLO for generic coloured massless final states. The cancellation of all explicit infrared poles appearing in the double-virtual contribution, in the real-virtual correction and in the integrated local infrared counterterms is explicitly verified, and all finite contributions arising from integrated local counterterms are analytically evaluated in terms of ordinary polylogarithms up to weight three. The resulting subtraction formula can readily be implemented in any numerical framework containing the relevant matrix elements up to NNLO.

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arXiv2023

NLO EW corrections to polarised W$^+$W$^-$ production and decay at the LHC

In this letter we present results for next-to-leading-order electroweak corrections to doubly polarised W$^+$W$^-$ production at the LHC in the fully leptonic decay channel. We model the production and the decay of two polarised W bosons in the double-pole approximation, including factorisable real and virtual electroweak corrections, and separating polarisation states at amplitude level. We obtain integrated and differential predictions for polarised signals in a realistic fiducial setup.

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