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Emanuele Re

Publications and source records attributed to Emanuele Re.

At least 19 recordsLinked to original sources
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

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

Boosted Higgs-strahlung off a $W$ boson at next-to-next-to-next-to-leading order in QCD

The production of a boosted Higgs boson in association with a charged weak ($W$) boson is a key process to scrutinize the electroweak symmetry breaking mechanism at hadron colliders. This reaction constitutes the dominant Higgs production channel at large transverse momentum, providing unique sensitivity to Higgs-boson interactions with other Standard Model particles as well as to physics beyond the Standard Model. In this Letter, we present the first fully differential calculation of this important scattering process at next-to-next-to-next-to-leading order (N$^3$LO) in perturbative Quantum Chromodynamics (QCD). We find that the N$^3$LO corrections, amounting to approximately $+2\%$ in the boosted regime, generally lie at the edge of or outside the standard scale variation band of the previous perturbative order. The residual dependence of the N$^3$LO prediction on perturbative scales is reduced to below the percent level, marking a milestone for the Higgs precision program.

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arXiv2026

Towards the inclusion of NLO EW corrections in the MiNLO method in Drell-Yan processes

In this paper we present the first application of the MiNLO method to the calculation of QED NLO corrections to the production of a neutral vector boson in Drell-Yan processes. We consider only the case of initial-state radiation, when the Z boson decays into neutrinos. We illustrate the abelianization procedure of the MiNLO formulae and discuss the impact that it has on the differential cross section. We then propose a variant of the MiNLO formulae in order to circumvent some of the problems that arise when dealing with QED emissions. Since this is a case study, we use ad-hoc parton distribution functions and a larger value of the electromagnetic coupling constant, in order to emphasize potential discrepancies with respect to the expected behavior of the MiNLO formulae. We quantify the uncertainties connected with the proposed method, also for a the physical value of the electromagnetic coupling. The study presented here is a necessary first step towards incorporating full electroweak effects into the MiNNLOPS framework.

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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

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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arXiv2025

Spin Correlations in $t{\bar t}$ Production and Decay at the LHC in QCD Perturbation Theory

In this work we consider the QCD predictions for spin correlations in $t\bar{t}$ production in hadronic collisions. In view of recent tensions between experimental data and theoretical calculations, it has been argued that one should include in the predictions also the effects of the production of the $\eta_t$, i.e. the pseudoscalar $t\bar{t}$ bound state, or alternatively the full effects of the non-relativistic dynamics of the $t\bar{t}$ pair near threshold. This implies the resummation of all corrections that scale like powers of $\alpha_s/v$ (where $v$ is the velocity of the top quark in the $t\bar{t}$ rest frame) which are dominated by values of $v$ of order $\alpha_s$. In this work, we show that, since the observables that are usually considered for these studies are integrated cross sections up to a $t\bar{t}$ mass cut that is not small, it is possible to perform the calculation using perturbation theory, considering only the contributions that scale as the first few powers of $\alpha_s/v$. We examine the implications of our approach by computing corrections to nominal Monte Carlo results for correlation-sensitive observables, and compare them with available data, showing that the tension with data is no longer present.

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arXiv2022

Momentum-space resummation for transverse observables and the Higgs $p_\perp$ at N$^3$LL+NNLO

We present an approach to the momentum-space resummation of global, recursive infrared and collinear safe observables featuring kinematic zeros away from the Sudakov limit. In the hadro-production of a generic colour singlet, we consider the family of inclusive observables which do not depend on the rapidity of the radiation, prime examples being the transverse momentum of the singlet, and $ϕ^*$ in Drell-Yan pair production. We derive a resummation formula valid up to next-to-next-to-next-to-leading-logaritmic accuracy for the considered observables. This formula reduces exactly to the customary resummation performed in impact-parameter space in the known cases, and it also predicts the correct power-behaved scaling of the cross section in the limit of small value of the observable. We show how this formalism is efficiently implemented by means of Monte Carlo techniques in a fully exclusive generator that allows one to apply arbitrary cuts on the Born variables for any colour singlet, as well as to automatically match the resummed results to fixed-order calculations. As a phenomenological application, we present state-of-the-art predictions for the Higgs-boson transverse-momentum spectrum at the LHC at next-to-next-to-next-to-leading-logarithmic accuracy matched to fixed next-to-next-to-leading order.

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arXiv2022

Next-to-next-to-leading order event generation for $VH$ production with $H\to b\bar{b}$ decay

We consider the Higgsstrahlung process in hadronic collisions and present the computation of next-to-next-to-leading order predictions matched to parton showers for both production and $H\to b\bar{b}$ decay employing the MiNNLO$_{\rm PS}$ method. We present predictions for $ZH$ and $W^{\pm}H$ production including spin correlations and off-shell effects by calculating the full processes $pp \to \ell^+\ell^-H \to \ell^+\ell^-b\bar{b}$, $pp \to ν_\ell\barν_\ell H \to ν_\ell\barν_\ell b\bar{b}$ and $pp \to \ell^\pm ν_\ell H \to \ell^\pm ν_\ell b\bar{b}$ in the narrow-width approximation for the Higgs boson. For the $W^{\pm}H$ process, NNLO+PS accuracy in production and decay is achieved for the first time. Our calculations are validated against earlier simulations in the NNLOPS approach that includes NNLO corrections via multi-differential reweighting. The new MiNNLO$_{\rm PS}$ generators for these processes, which evaluate NNLO corrections on-the-fly in the event generation, will supersede those earlier calculations. Our predictions are in good agreement with recent measurements of the Higgsstrahlung cross sections.

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arXiv2022

Theory uncertainties in the fiducial Drell-Yan cross section and distributions

In these proceedings we study various sources of theoretical uncertainty in the Drell-Yan $p_T^{\ell\ell}$ spectrum focussing on the $p_T^{\ell\ell} \lesssim 100\, {\rm GeV}$ region. We consider several perturbative aspects related to the choice of the scale setting adopted in resummed calculations, and we assess their impact on the theoretical prediction both for the differential $p_T^{\ell\ell}$ spectrum and for the $\rm{N}^3\rm{LO}$ fiducial cross section. For both quantities, we find the results obtained with the different setups to be compatible with each other within the quoted uncertainty, highlighting the robustness of the theoretical prediction. In all cases, the experimental LHC data for the $p_T^{\ell\ell}$ spectrum is well described by our calculation.

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arXiv2022

NNLO+PS Monte Carlo simulation of photon pair production with MiNNLOPS

We present a NNLO QCD accurate event generator for direct photon pair production at hadron colliders, based on the MiNNLOPS formalism, within the POWHEG BOX RES framework. Despite the presence of the photons requires the use of isolation criteria, our generator is built such that no technical cuts are needed at any stage of the event generation. Therefore, our predictions can be used to simulate kinematic distributions with arbitrary fiducial cuts. Furthermore, we describe a few modifications of the MiNNLOPS formalism in order to allow for a setting of the renormalization and factorization scales more similar to that of a fixed-order computation, thus reducing the numerical impact of higher-order terms beyond the nominal accuracy. Finally, we show several phenomenological distributions of physical interest obtained by showering the generated events with Pythia8, and we compare them with the 13 TeV data from the ATLAS Collaboration.

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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.

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arXiv2022

Next-to-next-to-leading order event generation for top-quark pair production

The production of top-quark pairs in hadronic collisions is among the most important reactions in modern particle physics phenomenology and constitutes an instrumental avenue to study the properties of the heaviest quark observed in nature. The analysis of this process at the Large Hadron Collider relies heavily on Monte Carlo simulations of the final state events, whose accuracy is challenged by the outstanding precision of experimental measurements. In this letter we present the first matched computation of top-quark pair production at next-to-next-to-leading order in QCD with all-order radiative corrections as implemented via parton-shower simulations. Besides its intrinsic relevance for LHC phenomenology, this work also establishes an important step towards the simulation of other hadronic processes with colour charges in the final state.

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arXiv2022

MiNNLO$_{\text{PS}}$: A new method to match NNLO QCD to parton showers

We present a novel method to combine QCD calculations at next-to-next-to-leading order (NNLO) with parton shower (PS) simulations, that can be applied to the production of heavy systems in hadronic collisions, such as colour singlets or a $t\bar{t}$ pair. The NNLO corrections are included by connecting the MiNLO$^\prime$ method with transverse-momentum resummation, and they are calculated at generation time without any additional reweighting, making the algorithm considerably efficient. Moreover, the combination of different jet multiplicities does not require any unphysical merging scale, and the matching preserves the structure of the leading logarithmic corrections of the Monte Carlo simulation for parton showers ordered in transverse momentum. We present proof-of-concept applications to hadronic Higgs production and the Drell-Yan process at the LHC.

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arXiv2021

Top-pair production at the LHC with MiNNLO$_{\rm PS}$

We consider the production of a pair of heavy quarks and illustrate the derivation of the MiNNLO method to match next-to-next-to-leading order calculations with parton showers (NNLO+PS) for this class of processes. As a first application, we construct an event generator for the fully differential simulation of hadronic top-quark pair production at NNLO+PS and discuss all details of its implementation in a parton shower Monte Carlo framework. We present new phenomenological results for the Large Hadron Collider obtained by including the tree-level decays of the top quarks, while accounting for spin-correlation effects. A comprehensive comparison to LHC measurements shows an excellent description of experimental data across multiple hadronic and leptonic particle-level observables. The computer code is available for download within the POWHEG-BOX.

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arXiv2021

HL-LHC Computing Review Stage-2, Common Software Projects: Event Generators

This paper has been prepared by the HEP Software Foundation (HSF) Physics Event Generator Working Group (WG), as an input to the second phase of the LHCC review of High-Luminosity LHC (HL-LHC) computing, which is due to take place in November 2021. It complements previous documents prepared by the WG in the context of the first phase of the LHCC review in 2020, including in particular the WG paper on the specific challenges in Monte Carlo event generator software for HL-LHC, which has since been updated and published, and which we are also submitting to the November 2021 review as an integral part of our contribution.

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arXiv2021

Fiducial Higgs and Drell-Yan distributions at N$^3$LL$^\prime$+NNLO with RadISH

We present state-of-the-art predictions for transverse observables relevant to colour-singlet production at the LHC, in particular the transverse momentum of the colour singlet in gluon-fusion Higgs production and in neutral Drell-Yan lepton-pair production, as well as the $ϕ^*_η$ observable in Drell Yan. We perform a next-to-next-to-next-to-leading logarithmic (N$^3$LL) resummation of such observables in momentum space according to the RadISH formalism, consistently including in our prediction all constant terms of relative order $α_s^3$ with respect to the Born, thereby achieving N$^3$LL$^\prime$ accuracy. The calculation is fully exclusive with respect to the Born kinematics, which allows the application of arbitrary fiducial selection cuts on the decay products of the colour singlet. We supplement our results with a transverse-recoil prescription, accounting for dominant classes of subleading-power corrections in a fiducial setup. The resummed predictions are matched with fixed-order differential spectra at next-to-next-to-leading order (NNLO) accuracy. A phenomenological comparison is carried out with 13 TeV LHC data relevant to the Higgs to di-photon channel, as well as to neutral Drell-Yan lepton-pair production. Overall, the inclusion of ${\cal O}(α_s^3)$ constant terms, and to a lesser extent of transverse-recoil effects, proves beneficial for the comparison of theoretical predictions to data, leaving a residual theoretical uncertainty in the resummation region at the 2-5% level for Drell-Yan observables, and 5-7% in Higgs production.

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