arXiv subjects

Aude Gehrmann-De Ridder

Publications and source records attributed to Aude Gehrmann-De Ridder.

45 records · Page 3Linked to original sources

arXiv2012

Double real radiation corrections to $t\bar{t}$ production at the LHC: the $gg\rightarrow t\bar{t}q\bar{q}$ channel

We present the double real radiation contributions to the $t \bar t$ hadronic production cross section stemming from the partonic process $gg\rightarrow t\bar{t}q\bar{q}$. We explicitly construct the antenna subtraction terms for this gluon-gluon initiated process starting from the double soft behaviour of the double real radiation matrix elements using soft currents. Those subtraction terms, given in leading and subleading colour contributions, require the use of new genuine NNLO four-parton antenna functions involving massive fermions. Those are also presented together with their infrared limits in this paper. We checked the validity of our subtraction terms numerically by showing that the ratio between the real radiation matrix elements and the subtraction terms approaches unity in all single and double unresolved regions of phase space.

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arXiv2012

Antenna subtraction with massive fermions at NNLO: Double real initial-final configurations

We derive the integrated forms of specific initial-final tree-level four-parton antenna functions involving a massless initial-state parton and a massive final-state fermion as hard radiators. These antennae are needed in the subtraction terms required to evaluate the double real corrections to $t\bar{t}$ hadronic production at the NNLO level stemming from the partonic processes $q\bar{q}\to t\bar{t}q'\bar{q}'$ and $gg\to t\bar{t}q\bar{q}$.

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arXiv2012

Antenna subtraction at NNLO with hadronic initial states: double real initial-initial configurations

The antenna subtraction method handles real radiation contributions in higher order corrections to jet observables. The method is based on antenna functions, which encapsulate all unresolved radiation between a pair of hard radiator partons. To apply this method to compute hadron collider observables, initial-initial antenna functions with both radiators in the initial state are required in unintegrated and integrated forms. In view of extending the antenna subtraction method to next-to-next-to-leading order (NNLO) calculations at hadron colliders, we derive the full set of initial-initial double real radiation antenna functions in integrated form.

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arXiv2011

Real-Virtual corrections for gluon scattering at NNLO

We use the antenna subtraction method to isolate the mixed real-virtual infrared singularities present in gluonic scattering amplitudes at next-to-next-to-leading order. In a previous paper, we derived the subtraction term that rendered the double real radiation tree-level process finite in the single and double unresolved regions of phase space. Here, we show how to construct the real-virtual subtraction term using antenna functions with both initial- and final-state partons which removes the explicit infrared poles present in the one-loop amplitude, as well as the implicit singularities that occur in the soft and collinear limits. As an explicit example, we write down the subtraction term that describes the single unresolved contributions from the five-gluon one-loop process. The infrared poles are explicitly and locally cancelled in all regions of phase space prior to integration, leaving a finite remainder that can be safely evaluated numerically in four-dimensions. We show numerically that the subtraction term correctly approximates the matrix elements in the various single unresolved configurations.

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arXiv2011

Antenna subtraction for the production of heavy particles at hadron colliders

The antenna subtraction method developed originally for the computation of higher order corrections to jet observables from a colourless initial state is extended for hadron collider processes involving a pair of massive particles and jets in the final state at the next-to-leading order (NLO) level. Due to the presence of coloured initial states, the subtraction terms need to be divided into three categories (final-final, initial-final and initial-initial). In this paper, we outline their construction and derive the necessary ingredients: phase space factorisation, antenna functions and also integrated antennae, including the effects of massive final states in all of those building parts. As a first application, we explicitly construct the colour-ordered real radiation and the corresponding antenna subtraction terms required at NLO for the production of a top quark pair and for the production of a top quark pair in association with a hard jet. The latter constitutes an essential ingredient for the computation of the hadronic production of a top-antitop pair at NNLO.

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arXiv2011

Antenna subtraction at NNLO with hadronic initial states: double real radiation for initial-initial configurations with two quark flavours

The antenna subtraction formalism allows to calculate QCD corrections to jet observables. Within this formalism, the subtraction terms are constructed using antenna functions describing all unresolved radiation between a pair of hard radiatior partons. In this paper, we focus on the subtraction terms for double real radiation contributions to jet observables in hadron-hadron collisions evaluated at NNLO. An essential ingredient to these subtraction terms are the four-parton antenna functions with both radiators in the initial state. We outline the construction of the double real subtraction terms, classify all relevant antenna functions and describe their integration over the relevant antenna phase space. For the initial-initial antenna functions with two quark flavours, we derive the phase space master integrals and obtain the integrated antennae.

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arXiv2010

NNLO antenna subtraction with two hadronic initial states

We discuss the extension of the antenna subtraction method to include two hadrons in the initial state (initial-initial antennae) at next-to-next-to-leading order. We sketch the construction of the subtraction terms and the required phase space transformations. We discuss the integration of the subtraction terms in detail.

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arXiv2010

NNLO Antenna Subtraction with One Hadronic Initial State

In this talk we present the extension of the antenna subtraction method to include initial states containing one hadron at NNLO. We sketch the requirements for the different necessary subtraction terms, and we explain how the antenna functions are integrated over the appropriate phase space by reducing the integrals to a small set of master integrals. Where applicable, our results for the integrated antennae were cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.

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arXiv2001

NLO QED corrections to ISR in e+ e- annihilation and the measurement of σ(e+ e- \to hadrons) using tagged photons

The leptonic tensor for the process $e^+ e^- \to γ+γ^*$, which describes the next-to-leading order virtual and soft QED corrections to initial state radiation in $e^+ e^-$ annihilation with emission of an extra virtual photon decaying into hadrons, is calculated. A Monte Carlo generator for the reaction $e^+ e^- \to γ+ π^+ π^-$ has been set up which includes these corrections. It thus describes configurations where the invariant mass of the hadrons plus photon is very close to $\sqrt{s}$. Predictions for cms energies of 1 to 10 GeV, corresponding to the energies of DAPHNE and B-meson factories, are presented. The possibility for an accurate measurement using tagged photons of $σ(e^+ e^- \to hadrons)$, which plays an important role in the theoretical description of the muon anomalous magnetic moment and the running of the electromagnetic coupling, is discussed.

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