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13 papers found.
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Extending the Minlo method

We consider improving Powheg+Minlo simulations, so as to also render them NLO accurate in the description of observables receiving contributions from events with lower parton multiplicity than present in their underlying NLO calculation. On a conceptual level we follow the strategy of the so-called Minlo ′ programs. Whereas the existing Minlo ′ framework requires explicit analytic ...

Spin polarisation of \(t\bar{t}\gamma \gamma \) production at NLO+PS with GoSam interfaced to MadGraph5_aMC@NLO

Eur. Phys. J. C Spin polarisation of t t¯γ γ production at NLO+PS with GOSAM interfaced to MADGRAPH5_AMC@NLO Hans van Deurzen 2 Rikkert Frederix 1 Valentin Hirschi 0 Gionata Luisoni 2 Pierpaolo

Automated NNLL \(+\) NLO resummation for jet-veto cross sections

In electroweak-boson production processes with a jet veto, higher-order corrections are enhanced by logarithms of the veto scale over the invariant mass of the boson system. In this paper, we resum these Sudakov logarithms at next-to-next-to-leading logarithmic accuracy and match our predictions to next-to-leading-order (NLO) fixed-order results. We perform the calculation in an ...

Merging meets matching in MC@NLO

The next-to-leading order accuracy for MC@NLO results exclusive in J light jets is achieved if the computation is based on matrix elements that feature J and J + 1 QCD partons. The simultaneous prediction of observables which are exclusive in different light-jet multiplicities cannot simply be obtained by summing the above results over the relevant range in J; rather, a suitable ...

aMCfast: automation of fast NLO computations for PDF fits

We present the interface between MadGraph5_aMC@NLO, a self-contained program that calculates cross sections up to next-to-leading order accuracy in an automated manner, and APPLgrid, a code that parametrises such cross sections in the form of look-up tables which can be used for the fast computations needed in the context of PDF fits. The main characteristic of this interface, ...

Single-top t-channel hadroproduction in the four-flavour scheme with POWHEG and aMC@NLO

We present results for the QCD next-to-leading order (NLO) calculation of single-top t-channel production in the 4-flavour scheme, interfaced to Parton Shower (PS) Monte Carlo programs according to the POWHEG and MC@NLO methods. Comparisons between the two methods, as well as with the corresponding process in the 5-flavour scheme are presented. For the first time results for ...

Automatic spin-entangled decays of heavy resonances in Monte Carlo simulations

We present a general method that allows one to decay narrow resonances in Les Houches Monte Carlo events in an efficient and accurate way. The procedure preserves both spin correlation and finite width effects to a very good accuracy, and is therefore particularly suited for the decay of resonances in production events generated at next-to-leading-order accuracy. The method is ...

NLO Higgs boson production plus one and two jets using the POWHEG BOX, MadGraph4 and MCFM

We present a next-to-leading order calculation of Higgs boson production plus one and two jets via gluon fusion interfaced to shower Monte Carlo programs, implemented according to the POWHEG method. For this implementation we have used a new interface of the POWHEG BOX with MadGraph4, that generates the codes for generic Born and real processes automatically. The virtual ...

NLO QCD corrections to five-jet production at LEP and the extraction of α s (M Z )

The highest exclusive jet multiplicity studied at LEP experiments is five. In this paper we compute the next-to-leading order QCD corrections to e + e − annihilation to five jets, essentially closing the (pure) perturbative QCD studies of exclusive jetty final states at LEP. We compare fixed-order perturbative results with ALEPH data. We estimate hadronization corrections to ...

aMC@NLO predictions for Wjj production at the Tevatron

We use aMC@NLO to predict the ℓν + 2-jet cross section at the NLO accuracy in QCD matched to parton shower simulations. We find that the perturbative expansion is well behaved for all the observables we study, and in particular for those relevant to the experimental analyses. We therefore conclude that NLO corrections to this process cannot be responsible for the excess of events ...

Four-lepton production at hadron colliders: aMC@NLO predictions with theoretical uncertainties

We use aMC@NLO to study the production of four charged leptons at the LHC, performing parton showers with both HERWIG and Pythia6. Our underlying matrix element calculation features the full next-to-leading order \( \mathcal{O}\left( {{\alpha_s}} \right) \) result and the \( \mathcal{O}\left( {\alpha_s^2} \right) \) contribution of the gg channel, and it includes all off-shell, ...

W and Z/γ ∗ boson production in association with a bottom-antibottom pair

We present a study of \( \ell \nu b\bar{b} \) and \( {\ell^{+} }{\ell^{-} }b\bar{b} \) production at hadron colliders. Our results, accurate to the next-to-leading order in QCD, are based on automatic matrix-element calculations performed by MadLoop and MadFKS, and are given at both the parton level, and after the matching with the Herwig event generator, achieved with aMC@NLO. We ...

Automation of one-loop QCD computations

We present the complete automation of the computation of one-loop QCD corrections, including UV renormalization, to an arbitrary scattering process in the Standard Model. This is achieved by embedding the OPP integrand reduction technique, as implemented in CutTools, into the MadGraph framework. By interfacing the tool so constructed, which we dub MadLoop, with MadFKS, the fully ...