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Sandro Uccirati

Publications and source records attributed to Sandro Uccirati.

At least 19 recordsLinked to original sources
arXiv2025

Advances in Local Analytic Sector Subtraction: massive NLO and elements of NNLO automation

In this article we present a number of developments within the scheme of Local Analytic Sector Subtraction for infrared divergences in QCD. First, we extend the scheme to deal with next-to-leading-order (NLO) singularities related to massive QCD particles in the final state. Then, we document a new implementation of the NLO subtraction scheme in the MADNKLO automated numerical framework, which is constructed to host higher-order subtraction algorithms. In particular, we discuss improvements in its performances with respect to the original implementation. Finally we describe the MADNKLO implementation of the first elements relevant to Local Analytic Sector Subtraction at next-to-next-to-leading order (NNLO), in the case of massless QCD partons in the final state.

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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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arXiv2022

Electroweak corrections to $g+g\to H_{l,h}$ and $H_{l,h}\toγ+γ$ in the Higgs-singlet extension of the Standard model

We calculate the next-to-leading order electroweak corrections for Higgs-boson production in gluon fusion and the Higgs-boson decay into two photons or gluons in the real Higgs-singlet extension of the Standard model (HSESM). For the light Higgs-boson of the HSESM the electroweak corrections for these processes are of the same order of magnitude as in the Standard model. For the heavy Higgs-boson of the HSESM the electroweak corrections can become large depending on the considered scenario.

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arXiv2022

Local analytic sector subtraction for initial- and final-state radiation at NLO in massless QCD

Within the framework of local analytic sector subtraction, we present the subtraction of next-to-leading-order QCD singularities for processes featuring massless coloured particles in the initial as well as in the final state. The features of the method are explained in detail, including the introduction of an optimisation procedure aiming at improving numerical stability at the cost of no extra analytic complexity. A numerical validation is provided for a variety of processes relevant to lepton as well as hadron colliders. This work constitutes a relevant step in view of the application of our subtraction method to processes involving initial-state radiation at next-to-next-to-leading order in QCD.

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arXiv2022

Strongly-ordered infrared limits for subtraction counterterms from factorisation

After a brief introduction to the problem of subtraction of infrared divergences for high-order collider observables, we present a preliminary study of strongly-ordered soft and collinear multiple radiation from the point of view of factorisation. We show that the matrix elements of fields and Wilson lines that describe soft and collinear radiation in factorised scattering amplitudes can be re-factorised in strongly-ordered limits, providing a systematic method to compute them, to characterise their singularity structure, and to build local subtraction counterterms for strongly-ordered configurations. Our results provide tools for a detailed organisation of subtraction algorithms, in principle to all orders in perturbation theory.

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arXiv2022

Analytic integration of soft and collinear radiation in factorised QCD cross sections at NNLO

Within the framework of local analytic sector subtraction, we present the full analytic integration of double-real and real-virtual local infrared counterterms that enter NNLO QCD computations with any number of massless final-state partons. We show that a careful choice of phase-space mappings leads to simple analytic results, including non-singular terms, that can be obtained with conventional integration techniques.

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arXiv2020

NLO QCD + electroweak predictions for off-shell ttH production at the LHC

In these proceedings, next-to-leading-order (NLO) QCD and electroweak (EW) corrections to ${\rm p}{\rm p} \to {\rm e}^+ ν_{\rm e} μ^- \bar ν_μ{\rm b} \bar{\rm b} {\rm H}$ at the LHC are presented. In these computations the top quarks are considered off their mass shell and all non-resonant contributions are included. The results are presented in the form of fiducial cross sections and differential distributions. Moreover, two prescriptions to combine QCD and EW corrections are examined.

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arXiv2019

Local Analytic Sector Subtraction at NNLO

We present a new method for the local subtraction of infrared divergences at next-to-next-to-leading order (NNLO) in QCD, for generic infrared-safe observables. Our method attempts to conjugate the minimal local counterterm structure arising from a sector partition of the radiation phase space with the simplifications following from analytic integration of the counterterms. In this first implementation, the method applies to final-state massless particles. We show how our method compactly organises infrared subtraction at NLO, we deduce in detail the general structure of the subtraction terms at NNLO, and we provide a proof of principle with a complete application to a simple process at NNLO.

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arXiv2018

Factorisation and Subtraction beyond NLO

We provide a general method to construct local infrared subtraction counterterms for unresolved radiative contributions to differential cross sections, to any order in perturbation theory. We start from the factorised structure of virtual corrections to scattering amplitudes, where soft and collinear divergences are organised in gauge-invariant matrix elements of fields and Wilson lines, and we define radiative eikonal form factors and jet functions which are fully differential in the radiation phase space, and can be shown to cancel virtual poles upon integration by using completeness relations and general theorems on the cancellation of infrared singularities. Our method reproduces known results at NLO and NNLO, and yields substantial simplifications in the organisation of the subtraction procedure, which will help in the construction of efficient subtraction algorithms at higher orders.

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arXiv2018

Electroweak corrections in the 2HDM for neutral scalar Higgs-boson production through gluon fusion

We have computed the two-loop, electroweak corrections to the production of a light and a heavy neutral, scalar Higgs-boson through the important gluon fusion process in the Two-Higgs-Doublet Model. We provide our results in various renormalization schemes for different scenarios and benchmark points, which will be valuable for experimental studies at the LHC. We describe the technicalities of our two-loop calculation and augment it by a phenomenological discussion. Our results are also applicable to the gluonic neutral, scalar Higgs-boson decays.

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arXiv2018

Towards analytic local sector subtraction at NNLO

A new method for local subtraction at next-to-next-to-leading order in QCD is sketched, attempting to conjugate the minimal counterterm structure arising from a sector partition of the radiation phase space with the simplifications following from analytic integration of the counterterms.

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arXiv2018

Factorization and subtraction

We explore the connection between the factorisation of virtual corrections to multi-particle massless gauge theory amplitudes and the problem of subtraction at NNLO and beyond. Taking inspiration from virtual factorisation, we provide a set of definitions for local soft and collinear counterterms, expressed in terms of matrix elements of operators involving fields and Wilson lines, and valid to all orders in perturbation theory. We hope that the connection between factorisation and subtraction will help in the construction of minimal, stable, and efficient subtraction algorithms, taking maximal advantage of existing analytic information.

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arXiv2018

Recola2: REcursive Computation of One-Loop Amplitudes 2

We present the Fortran95 program Recola2 for the perturbative computation of next-to-leading-order transition amplitudes in the Standard Model of particle physics and extended Higgs sectors. New theories are implemented via model files in the 't Hooft-Feynman gauge in the conventional formulation of quantum field theory and in the Background-Field method. The present version includes model files for the Two-Higgs-Doublet Model and the Higgs-Singlet Extension of the Standard Model. We support standard renormalization schemes for the Standard Model as well as many commonly used renormalization schemes in extended Higgs sectors. Within these models the computation of next-to-leading-order polarized amplitudes and squared amplitudes, optionally summed over spin and colour, is fully automated for any process. Recola2 allows the computation of colour- and spin-correlated leading-order squared amplitudes that are needed in the dipole subtraction formalism. Recola2 is publicly available for download at http://recola.hepforge.org.

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arXiv2017

Recola2: a one-loop matrix-element generator for BSM theories and SM effective field theory

We present the Recola2 library for the efficient generation and computation of one-loop amplitudes in Beyond-Standard-Model theories. Recola2 is based on Recola, an efficient one-loop amplitude generator for the Standard Model, and Rept1l, a newly developed tool to generate one-loop model files for Recola2 in a fully automated way. Recola2 is able to operate with non-trivial extensions of the SM, e.g. extended Higgs sectors and effective field theories. We discuss first applications to extended Higgs sectors and their renormalization.

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arXiv2017

NLO QCD and EW corrections to processes involving off-shell top quarks

We review recent results on next-to-leading order (NLO) QCD and electroweak (EW) corrections for processes involving off-shell top quarks. For the off-shell production of two top quarks that decay leptonically, the full NLO EW corrections have been computed. For the very same process in association with a Higgs boson, EW corrections have been calculated and combined with existing NLO QCD corrections. In both cases, selected differential distributions are shown. In these proceedings, particular emphasis is put on the effect of the EW corrections as well as the off-shell contributions.

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arXiv2017

NLO electroweak corrections in extended Higgs Sectors with RECOLA2

We present the computer code RECOLA2 along with the first NLO electroweak corrections to Higgs production in vector-boson fusion and updated results for Higgs strahlung in the Two-Higgs-Doublet Model and Higgs-Singlet extension of the Standard Model. A fully automated procedure for the generation of tree-level and one-loop matrix elements in general models, including renormalization, is presented. We discuss the application of the Background-Field Method to the extended models. Numerical results for NLO electroweak cross sections are presented for different renormalization schemes in the Two-Higgs-Doublet Model and the Higgs-Singlet extension of the Standard Model. Finally, we present distributions for the production of a heavy Higgs boson.

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arXiv2017

Higgs production in association with off-shell top-antitop pairs at NLO EW and QCD at the LHC

We present NLO electroweak corrections to Higgs production in association with off-shell top-antitop quark pairs. The full process $\text{p}\text{p}\to\text{e}^+ν_{\text{e}} μ^-\barν_μ\text{b}\bar{\text{b}} \text{H}$ is considered, and hence all interference, off-shell, and non-resonant contributions are taken into account. The electroweak corrections turn out to be below one per cent for the integrated cross section but can exceed $10\%$ in certain phase-space regions. In addition to its phenomenological relevance, the computation constitutes a major technical achievement as the full NLO virtual corrections involving up to 9-point functions have been computed exactly. The results of the full computation are supported by two calculations in the double-pole approximation. These also allow to infer the effect of off-shell contributions and emphasise their importance especially for the run II of the LHC. Finally, we present combined predictions featuring both NLO electroweak and QCD corrections in a common set-up that will help the experimental collaborations in their quest of precisely measuring the aforementioned process.

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