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The strongest constraint on Vtb presently comes from the 3 × 3 unitarity of the CKM matrix, which fixes Vtb to be very close to one. If unitarity is relaxed, current information from top production at Tevatron still leaves open the possibility that Vtb is sizably smaller than one. In minimal extensions of the standard model with extra heavy quarks, the unitarity constraints are much weaker, and th
We present the latest developments of the MadGraph/MadEvent Monte Carlo event generator and several applications to hadron collider physics. In the current version events at the parton, hadron and detector level can be generated directly from a web interface, for arbitrary processes in the Standard Model and in several physics scenarios beyond it (HEFT, MSSM, 2HDM). The most important additions ar
The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of J / ψ vector mesons off proton targets in ultra–peripheral p–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02 TeV. The e + e - and μ + μ - decay channels are used to measure the cross section as a function of the rapidity of the J / ψ in the range - 2.5 < y< 2.7 , corresponding to an energy
The new version of the MadGraph/MadEvent (MG/ME) MC generator is introduced by emphasizing its easy-to-use way of incorporating new models and generating events. As an application, a study of t t production in various scenarios beyond the standard model is presented.
We explore in detail the physics potential of a measurement of the t invariant mass distribution. First, we assess the accuracy of the best available predictions for this observable and find that in the low invariant mass region, the shape is very well predicted and could be used to perform a top mass measurement. Second, we study the effects of a heavy s-channel resonance on the t invariant mass
We present a consistent analysis of the signal as well as the irreducible background for the search of the SM Higgs boson in the ZZ decay channel at the LHC. Soft-gluons effects are resummed up to next-to-leading logarithmic accuracy, and the results are compared to those obtained with fixed order calculations and the MC@NLO event generator. The soft-gluon effects are typically modest but should b
We present the implementation of the dipole subtraction formalism for the real radiation contributions to any next-to-leading order QCD process in the MadGraph/MadEvent framework. Both massless and massive dipoles are considered. Starting from a specific (n+1)-particle process the package provides a Fortran code for all possible dipoles to all Born processes that constitute the subtraction term to
We here present some recent developments of MadGraph/MadEvent since the latest published version, 4.0. These developments include: Jet matching with Pythia parton showers for both Standard Model and Beyond the Standard Model processes, decay chain functionality, decay width calculation and decay simulation, process generation for the Grid, a package for calculation of quarkonium amplitudes, calcul
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
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
