Search results

This paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV proton–proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb −1 are used. Two channels are considered, depending on the leptonic or the hadronic decays of the W boson from the top qu

We present the predictions at next-to-leading order (NLO) in the strong coupling for the single-top cross section in the t channel at the Tevatron and the LHC. Our calculation starts from the 2→3 Born amplitude gq→tb̄q′, keeping the b-quark mass nonzero. A comparison is performed with a traditional NLO calculation of this channel based on the 2→2 Born process with a bottom quark in the initial sta

We present updated NLO predictions for the electroweak t-channel production of heavy quarks at the Tevatron and at the LHC. We consider production of single top and fourth generation t′ starting from both 2 → 2 and 2→3 Born processes. Predictions for tb′ and t′b′ cross sections at NLO are also given for the first time. A thorough study of the theoretical uncertainties coming from parton distributi

We present the complete automation of the universal subtraction formalism proposed by Frixione, Kunszt, and Signer for the computation of any cross section at the next-to-leading order in QCD. Given a process, the only ingredient to be provided externally is the infrared- and ultraviolet-finite contribution of virtual origin. Our implementation, currently restricted to the case of e + e - colli

In this talk we give an overview of the existing codes that aim for the automation of the subtraction terms in next-to-leading order calculations in perturbative QCD.

Heading towards a full automation of next-to-leading order (NLO) QCD corrections, one important ingredient is the analytical integration over the one-particle phase space of the unresolved particle that is necessary when adding the subtraction terms to the virtual corrections. We present the implementation of these integrated dipoles in the MadGraph framework. The result is a package that allows a

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 five-jet observables us

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In this talk the FKS subtraction method for next-to-leading order (in QCD) computations is reviewed and its automation in the computer code MadFKS is presented. As a proof of concept, some results in the form of plots for distributions at next-to-leading order in e+e− → 2, 3 and 4 jets are shown by interfacing this code to BlackHat and Rocket.

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 automatic computat

We present the calculation of scalar and pseudoscalar Higgs production in association with a top-antitop pair to the next-to-leading order (NLO) accuracy in QCD, interfaced with parton showers according to the MC@NLO formalism. We apply our results to the cases of light and very light Higgs boson production at the LHC, giving results for total rates as well as for sample differential distributions

We present a study of lνbb and l++l-bb production at hadron colliders. Our results, accurate to the next-to-leading order in QCD, are based on automatic matrix-element calculations performed byMadLoop andMadFKS, and are given at both the parton level, and after the matching with the Herwig event generator, achieved with aMC@NLO. We retain the complete dependence on the bottom-quark mass, and inclu

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 O(α S) result and the O(α S 2) contribution of the gg channel, and it includes all off-shell, spin-correlation, virtualphoton-exchange, and interference effects. We present several key di

We use aMC@NLO to predict the ℓ? + 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 in the dijet inva

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 typical kinematic dist

In this talk we give an overview of the theory status for the predictions of W boson production in association with bottom quarks with relevance to top quark phenomenology.