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A bstract We present a novel method to combine QCD calculations at next-to-next-to-leading order (NNLO) with parton shower (PS) simulations, that can be applied to the production of heavy systems in hadronic collisions, such as colour singlets or a t t ¯ pair. The NNLO corrections are included by connecting the M i NLO′ method with transverse- momentum resummation, and they are calculated at generation time without any additional reweighting, making the algorithm considerably efficient. Moreover, the combination of different jet multiplicities does not require any unphysical merging scale, and the matching preserves the structure of the leading logarithmic corrections of the Monte Carlo simulation for parton showers ordered in transverse momentum. We present proof-of-concept applications to hadronic Higgs production and the Drell-Yan process at the LHC.

We present the matching of NLO QCD and NLO EW corrections to parton showers for vector-boson pair production at the LHC. We consider leptonic final states, including resonant and non-resonant diagrams, spin correlations and off-shell effects. Our results are obtained interfacing the Recola2-Collier one-loop provider with the POWHEG-BOX-RES framework. We discuss our implementation, we validate it at fixed order, and we show our final results matched to parton shower. A by-product of our work is also a general interface between Recola2-Collier and POWHEG-BOX-RES. This is the first time that EW and QCD corrections to diboson production are consistently matched to parton showers.

A bstract We present the combination of fully differential cross sections for colour-singlet production processes at next-to-next-to-leading order (NNLO) QCD obtained with M atrix and all-order resummation through R ad ISH. This interface allows us to achieve unprecedented accuracy for various transverse observables in 2 → 2 production processes. As an important application we consider W + W − production at the LHC, more precisely the full leptonic process pp → ℓ + ℓ ′ − ν ℓ ν ¯ ℓ ′ + X with ℓ ′ ≠ ℓ , and we present resummed predictions for differential distributions in presence of fiducial selection cuts. In particular, we resum the transverse-momentum spectrum of the W + W − pair at next-to-next-to-next-to-leading logarithmic (N 3 LL) accuracy and match it to the integrated NNLO cross section. The transverse-momentum spectrum of the leading jet in W + W − production is calculated at NNLO+NNLL accuracy. Finally, the joint resummation for the transverse-momentum spectrum of the W + W − pair in the presence of a jet veto is performed at NNLO+NNLL. Our phenomenological study highlights the importance of higher-order perturbative and logarithmic corrections for precision phenomenology at the LHC.

A bstract Stringent limits on the interactions between dark matter (DM) and the standard model (SM) can be set by studying how initial-state or final-state particles recoil against missing transverse energy . In this work, we improve, extend and correct LHC constraints on the interactions between DM and top quarks that are mediated by the exchange of spin-0 s -channel resonances. A comparison of the LHC run-1 sensitivity of the two main search channels is presented, which shows that mono-jet searches are typically more restrictive than the searches. We furthermore explore the reach of the 14 TeV LHC. The collider constraints are compared to the restrictions arising from direct and indirect detection as well as the DM relic abundance, and we also reflect on effective field theory (EFT) interpretations of the LHC exclusions.

In this work we illustrate the POWHEG BOX , a general computer code framework for implementing NLO calculations in shower Monte Carlo programs according to the POWHEG method. Aim of this work is to provide an illustration of the needed theoretical ingredients, a view of how the code is organized and a description of what a user should provide in order to use it.

A bstract We detail a simulation of Higgs boson production via gluon fusion, accurate at next-to-next-to-leading order in the strong coupling, including matching to a parton shower, yielding a fully exclusive, hadron-level description of the final-state. The approach relies on the P owheg method for merging the NLO Higgs plus jet cross-section with the parton shower, and on the M inlo method to simultaneously achieve NLO accuracy for inclusive Higgs boson production. The NNLO accuracy is reached by a reweighting procedure making use of the H nnlo program.

A bstract We present novel predictions for the production of W + W − pairs in hadron collisions that are next-to-next-to-leading order accurate and consistently matched to a parton shower (NNLOPS). All diagrams that lead to the process pp → e − ν ¯ e μ + ν μ + X are taken into account, thereby including spin correlations and off-shell effects. For the first time full NNLOPS accuracy is achieved for a 2 → 4 process. We find good agreement, at the 1 σ level, with the W + W − rates measured by ATLAS and CMS. The importance of NNLOPS predictions is evident from differential distributions sensitive to soft-gluon effects and from the large impact (10% and more) of including next-to-next-to-leading order corrections on top of M i NLO. We define a charge asymmetry for the W bosons and the leptons in W + W − production at the LHC, which is sensitive to the W polarizations and hence can be used as a probe of new physics.

A bstract We present state-of-the-art predictions for transverse observables relevant to colour-singlet production at the LHC, in particular the transverse momentum of the colour singlet in gluon-fusion Higgs production and in neutral Drell-Yan lepton-pair production, as well as the ϕ η ∗ observable in Drell Yan. We perform a next-to-next-to-next-to-leading logarithmic (N 3 LL) resummation of such observables in momentum space according to the RadISH formalism, consistently including in our prediction all constant terms of relative order α s 3 with respect to the Born, thereby achieving N 3 LL′ accuracy. The calculation is fully exclusive with respect to the Born kinematics, which allows the application of arbitrary fiducial selection cuts on the decay products of the colour singlet. We supplement our results with a transverse-recoil prescription, accounting for dominant classes of subleading-power corrections in a fiducial setup. The resummed predictions are matched with fixed-order differential spectra at next-to-next-to-leading order (NNLO) accuracy. A phenomenological comparison is carried out with 13 TeV LHC data relevant to the Higgs to di-photon channel, as well as to neutral Drell-Yan lepton-pair production. Overall, the inclusion of O ( α s 3 ) constant terms, and to a lesser extent of transverse-recoil effects, proves beneficial for the comparison of theoretical predictions to data, leaving a residual theoretical uncertainty in the resummation region at the 2–5% level for Drell-Yan observables, and 5–7% in Higgs production.

A bstract 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 distributions of the spectator- b jet are presented in an NLO + PS approach.

We consider the MiNNLO PS method to consistently combine next-to-next-to-leading order (NNLO) QCD calculations with parton-shower simulations. We identify the main sources of differences between MiNNLO PS and fixed-order NNLO predictions for inclusive observables due to corrections beyond NNLO accuracy and present simple prescriptions to either reduce or remove them. Refined predictions are presented for Higgs, charged- and neutral-current Drell Yan production. The agreement with fixed-order NNLO calculations is considerably improved for inclusive observables and scale uncertainties are reduced. The codes are released within the POWHEG-BOX .