Search

This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations., The authors would like to thank Daniel Whiteson for helping in the review of this document. This research was supported by the Munich Institute for Astro- and Particle Physics (MIAPP) of the DFG cluster of excellence "Origin and Structure of the Universe''. The authors would like to express a special thanks to the Mainz Institute for Theoretical Physics (MITP) for its hospitality and support. P. Pani wishes to thank the support of the Computing Infrastructure of Nikhef. In addition we thank CERN and acknowledge the support of: DOE and NSF (USA), including grant DE-SC0011726 for the preparation of this manuscript; SER, SNSF and Cantons of Bern and Geneva, Switzerland; MINECO, Spain; European Union, where the preparation of this manuscript is part of a project that has received funding from the European Research Council under the European Union's Horizon 2020 research and innovation program (grant agreement 679305); IN2P3-CNRS, CEA-DSM/IRFU, France; NSERC, NRC, and CFI, Canada; INFN, Italy; FNRS and FWO, Belgium; STFC, United Kingdom; ARC, Australia; GRICES and FCT, Portugal; SRC, Sweden; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; Austrian Academy of Sciences, Austria; MOE and UM, Malaysia; National Research Foundation and Ministry of Education, Science and Technology, Korea; MEXT and JSPS, Japan; FOM and NWO, Netherlands; CNPq and FAPESP, Brazil; Atomic Energy Commission, Pakistan; DNRF, DNSRC and Lundbeck Foundation, Denmark; Thailand Center of Excellence in Physics, Institute for the Promotion of Teaching Science and Technology, Special Task Force for Activating Research and National Science and Technology Development Agency, Thailand; MOST, Taiwan., info:eu-repo/semantics/publishedVersion

The Drell-Yan process at hadron colliders is a fundamental benchmark for the study of strong interactions and the extraction of electroweak parameters. The outstanding precision of the LHC demands very accurate theoretical predictions with a full account of fiducial experimental cuts. In this Letter we present a state-of-the-art calculation of the fiducial cross section and of differential distributions for this process at third order in the strict fixed-order expansion in the strong coupling, as well as including the all-order resummation of logarithmic corrections. Together with these results, we present a detailed study of the subtraction technique used to carry out the calculation for different sets of experimental cuts, as well as of the sensitivity of the fiducial cross section to infrared physics. We find that residual theory uncertainties are reduced to the percent level and that the robustness of the predictions can be improved by a suitable adjustment of fiducial cuts. The Drell-Yan process at hadron colliders is a fundamental benchmark for the study of strong interactions and the extraction of electro-weak parameters. The outstanding precision of the LHC demands very accurate theoretical predictions with a full account of fiducial experimental cuts. In this letter we present a state-of-the-art calculation of the fiducial cross section and of differential distributions for this process at third order in the strict fixed-order expansion in the strong coupling, as well as including the all-order resummation of logarithmic corrections. Together with these results, we present a detailed study of the subtraction technique used to carry out the calculation for different sets of experimental cuts, as well as of the sensitivity of the fiducial cross section to infrared physics. We find that residual theory uncertainties are reduced to the percent level and that the robustness of the predictions can be improved by a suitable adjustment of fiducial cuts.

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 $\phi^*_\eta$ 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 $\alpha_s^3$ with respect to the Born, thereby achieving N$^3$LL$^\prime$ 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 ${\cal O}(\alpha_s^3)$ 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., Comment: 35 pages, 9 figures. Journal version

The production of top-quark pairs in hadronic collisions is among the most important reactions in modern particle physics phenomenology and constitutes an instrumental avenue to study the properties of the heaviest quark observed in nature. The analysis of this process at the Large Hadron Collider relies heavily on Monte Carlo simulations of the final state events, whose accuracy is challenged by the outstanding precision of experimental measurements. In this letter we present the first matched computation of top-quark pair production at next-to-next-to-leading order in QCD with all-order radiative corrections as implemented via parton-shower simulations. Besides its intrinsic relevance for LHC phenomenology, this work also establishes an important step towards the simulation of other hadronic processes with colour charges in the final state., Journal version

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 MATRIX and all-order resummation through RadISH. This interface allows us to achieve unprecedented accuracy for various transverse observables in $2 \rightarrow 2$ production processes. As an important application we consider $W^+ W^-$ production at the LHC, more precisely the full leptonic process $pp\to \ell^+\ell^{\prime\, -}\nu_{\ell}{\bar\nu}_{\ell^\prime}+X$ with $\ell'\neq\ell$, 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., Comment: 47 pages, 7 figures, 2 tables; corresponds to the version published on JHEP

We perform a phenomenological study of $Z$ plus jet, Higgs plus jet and di-jet production at the Large Hadron Collider. We investigate in particular the dependence of the leading jet cross section on the jet radius as a function of the jet transverse momentum. Theoretical predictions are obtained using perturbative QCD calculations at the next-to and next-to-next-to-leading order, using a range of renormalization and factorization scales. The fixed order predictions are compared to results obtained from matching next-to-leading order calculations to parton showers. A study of the scale dependence as a function of the jet radius is used to provide a better estimate of the scale uncertainty for small jet sizes. The non-perturbative corrections as a function of jet radius are estimated from different generators., Comment: 23 pages, 19 figures

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., Comment: Added figs.6-7. Extended discussion in sect.5. Matches version published on epjc

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 $t\bar{t}$ pair. The NNLO corrections are included by connecting the MiNLO$^\prime$ 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., Comment: Fixed sign typo in Eq. (4.24)

We present predictions for $W^+W^-$ production (with exact decays) that are next-to-next-to-leading order (NNLO) accurate and consistently matched to a parton shower. The matching is achieved by upgrading, with MiNLO, the NLO calculation of $W^+W^- +1$ jet production, in such a way that NLO accuracy is guaranteed for $W^+W^-$ inclusive observables, and by performing subsequently a reweighting of the WWJ-MiNLO events, differential in the $W^+W^-$ Born variables, to the NNLO results obtained with MATRIX., Comment: 7 pages, 2 figures. Submitted to the proceedings of the XXVI International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2018, April 16-20, 2018, Kobe, Japan

We present an approach to the momentum-space resummation of global, recursive infrared and collinear safe observables featuring kinematic zeros away from the Sudakov limit. In the hadro-production of a generic colour singlet, we consider the family of inclusive observables which do not depend on the rapidity of the radiation, prime examples being the transverse momentum of the singlet, and $\phi^*$ in Drell-Yan pair production. We derive a resummation formula valid up to next-to-next-to-next-to-leading-logaritmic accuracy for the considered observables. This formula reduces exactly to the customary resummation performed in impact-parameter space in the known cases, and it also predicts the correct power-behaved scaling of the cross section in the limit of small value of the observable. We show how this formalism is efficiently implemented by means of Monte Carlo techniques in a fully exclusive generator that allows one to apply arbitrary cuts on the Born variables for any colour singlet, as well as to automatically match the resummed results to fixed-order calculations. As a phenomenological application, we present state-of-the-art predictions for the Higgs-boson transverse-momentum spectrum at the LHC at next-to-next-to-next-to-leading-logarithmic accuracy matched to fixed next-to-next-to-leading order., Comment: Added short appendix on small pt scaling

The perturbative description of certain differential distributions across a wide kinematic range requires the matching of fixed-order perturbation theory with resummation of large logarithmic corrections to all orders. We present precise matched predictions for transverse-momentum distributions in Higgs boson (H) and Drell-Yan pair (DY) production as well as for the closely related ϕ η * distribution at the LHC. The calculation is exclusive in the Born kinematics, and allows for arbitrary fiducial selection cuts on the decay products of the colour singlets, which is of primary relevance for experimental analyses. Our predictions feature very small residual scale uncertainties and display a good convergence of the perturbative series. A comparison of the predictions for DY observables to experimental data at 8 TeV shows a very good agreement within the quoted errors., Journal of High Energy Physics, 2018 (12), ISSN:1126-6708, ISSN:1029-8479

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 $pp\to e^- \bar \nu_e\;\mu^+\nu_\mu+X$ are taken into account, thereby including spin correlations and off-shell effects. For the first time full NNLOPS accuracy is achieved for a $2\to 4$ process. We find good agreement, at the 1$\sigma$ 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 MiNLO. 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., Comment: 40 pages, 11 figures, 3 tables

I give an overview of recent progress in the simulation of final states involving top-quarks and vector bosons pair. First I'll discuss the recently found solutions needed to simulate fully differential top pair production ($pp\to b\bar{b}$ + 4 leptons) at NLO+PS accuracy, retaining off-shellness and interference effects exactly. In the second part, I'll review the MiNLO (Multi-scale Improved NLO) method, and then show a recent application, namely the simultaneous NLO+PS description of $W^+W^-$ and $W^+W^- +$ 1 jet production., Comment: 6 pages, 2 figures. Submitted to the proceedings of the 38th International Conference on High Energy Physics, ICHEP2016, 3-10 August, 2016, Chicago, USA

We propose a novel strategy to constrain the bottom and charm Yukawa couplings by exploiting LHC measurements of transverse momentum distributions in Higgs production. Our method does not rely on the reconstruction of exclusive final states or heavy-flavour tagging. Compared to other proposals it leads to an enhanced sensitivity to the Yukawa couplings due to distortions of the differential Higgs spectra from emissions which either probe quark loops or are associated to quark-initiated production. We derive constraints using data from LHC Run I, and we explore the prospects of our method at future LHC runs. Finally, we comment on the possibility of bounding the strange Yukawa coupling., Added analysis of the Higgs transverse momentum distribution. Version published in Physical Review Letters

We present a simulation program for the production of a pair of W bosons in association with a jet, that can be used in conjunction with general-purpose shower Monte Carlo generators, according to the POWHEG method. We have further adapted and implemented the MINLO' method on top of the NLO calculation underlying our WW+jet generator. Thus, the resulting simulation achieves NLO accuracy not only for inclusive distributions in WW+jet production but also WW production, i.e. when the associated jet is not resolved, without the introduction of any unphysical merging scale. This work represents the first extension of the MINLO' method, in its original form, to the case of a genuine underlying 2->2 process, with non-trivial virtual corrections., 22 pages, 9 figures

The latest LHC mono-jet searches place stringent bounds on the pp -> chibar chi cross section of dark matter. Further properties such as the dark matter mass or the precise structure of the interactions between dark matter and the standard model can however not be determined in this manner. We point out that measurements of the azimuthal angle correlations between the two jets in 2 j + chibar chi events may be used to disentangle whether dark matter pair production proceeds dominantly through tree or loop diagrams. Our general observation is illustrated by considering theories in which dark matter interacts predominantly with the top quark. We show explicitly that in this case the jet-jet azimuthal angle difference is a gold-plated observable to probe the Lorentz structure of the couplings of dark matter to top quarks, thus testing the CP nature of the particle mediating these interactions., 8 pages, 5 figures; v2: discussion of signal and background cross sections added, labelling of plots improved, typos fixed and references updated; matches version published in PRD

We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross Section Working Group., Comment: Minor changes, plots updated, matches the version published in JHEP

I summarize the state of the art of cross-section computations and of available simulation tools for top-quark pair production in hadron collisions. Particular emphasis is put on recent theory developments relevant for LHC phenomenology., Very minor changes (after comments by the editors). It matches the version to appear on PoS

We propose a new approach to the resummation of the transverse-momentum distribution of a high-mass colour-singlet system in hadronic collisions. The resummation is performed in momentum space and is free of kinematic singularities at small transverse momentum. We derive a formula accurate at the next-to-next-to-leading-logarithmic level, and present the first matched predictions to next-to-next-to-leading order for Higgs-boson production in gluon fusion at the LHC. This method can be adapted to all observables featuring kinematic cancellations in the infrared region.

This document a59Summary of the discussions and conclusions following from Dark Matter @ LHC 2014, held at Merton College, Oxford, on September 25-27, 2014. outlines a set of simplified models for dark matter and its interactions with Standard Model particles. It is intended to summarize the main characteristics that these simplified models have when applied to dark matter searches at the LHC, and to provide a number of useful expressions for reference. The list of models includes both s-channel and t-channel scenarios. For s-channel, spin-0 and spin-1 mediations are discussed, and also realizations where the Higgs particle provides a portal between the dark and visible sectors. The guiding principles underpinning the proposed simplified models are spelled out, and some suggestions for implementation are presented., 0, SCOPUS: ar.j, info:eu-repo/semantics/published

The LHCb collaboration has recently performed a first measurement of the angular production asymmetry in the distribution of beauty quarks and anti-quarks at a hadron collider. We calculate the corresponding standard model prediction for this asymmetry at fixed-order in perturbation theory. Our results show good agreement with the data, which is provided differentially for three bins in the invariant mass of the $b \bar b$ system. We also present similar predictions for both beauty-quark and charm-quark final states within the LHCb acceptance for a collision energy of $\sqrt{s} = 13 \, {\rm TeV}$. We finally point out that a measurement of the ratio of the $b \bar b$ and $c \bar c$ cross sections may be useful for experimentally validating charm-tagging efficiencies., Comment: 4.5 pages + references, 1 figure, 4 tables

We present a next-to-leading order (NLO) calculation of $t\bar{t}$ production in hadronic collisions interfaced to shower generators according to the POWHEG method. We start from an NLO result from previous work, obtained in the zero width limit, where radiative corrections to both production and decays are included. The POWHEG interface required an extension of the POWHEG BOX framework, in order to deal with radiation from the decay of resonances. This extension is fully general (i.e. it can be applied in principle to any process considered in the zero width limit), and is here applied for the first time. In order to perform a realistic simulation, we introduce finite width effects using different approximations, that we validated by comparing with published exact NLO results. We have interfaced our POWHEG code to the PYTHIA8 shower Monte Carlo generator. At this stage, we dealt with novel issues related to the treatment of resonances, especially with regard to the initial scale for the shower that needs to be set appropriately. This procedure affects, for example, the fragmentation function of the b quark, that we have studied with particular attention. We believe that the tool presented here improves over previous generators for all aspects that have to do with top decays, and especially for the study of issues related to top mass measurements that involve B hadrons or b jets. The work presented here also constitutes a first step towards a fully consistent matching of NLO calculations involving intermediate resonances decaying into coloured particles, with parton showers., Comment: Minor changes: improved few sentences, added 1 explanatory figure in sec. 1. Now it matches the version published in JHEP

Stringent limits on the interactions between dark matter (DM) and the standard model can be set by studying how initial-state or final-state particles recoil against missing transverse energy (MET). 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 MET + tbar t 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 interpretations of the LHC exclusions., Comment: 29 pages, 11 figures; v4: conflict with CERN-PH-TH number fixed

We present a next-to-next-to-leading order accurate description of Drell-Yan lepton pair production processes through $\gamma^*/Z$ or $W$ exchange that includes consistently parton shower effects. Results are obtained by upgrading the vector-boson plus one jet NLO calculation in POWHEG with the MiNLO procedure and by applying an appropriate reweighting procedure making use of the DYNNLO program. We compare to existing data and to accurate resummed calculations., Comment: 31 pages, 17 figures, 1 table

After the discovery of the 125 GeV scalar boson with gauge properties similar to the Standard Model (SM) Higgs, the search for beyond the SM interactions will focus on studying the discovered particles' coupling properties more precisely and shedding light on the relation of fermion masses with the electroweak vacuum. The large mass of the top quark and the SM-predicted order one top Yukawa coupling is a natural candidate for beyond the SM physics, though experimentally challenging to constrain. In this paper, we argue that investigating angular correlations in $pp\ensuremath{\rightarrow}tHj$ production provides an excellent handle to constrain the top Yukawa coupling ${y}_{t}$ via direct measurements, even when we focus on rare exclusive final states. We perform a hadron-level analysis and show that we may expect to constrain ${y}_{t}\ensuremath{\gtrsim}0.5{y}_{t}^{\mathrm{SM}}$ at 95%--99% confidence level at the high luminosity LHC using semileptonic top decays and $H\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$ alone, by employing a two-channel measurement approach.

Extensions of the Standard Model Higgs sector involving weak isotriplet scalars are not only benchmark candidates to reconcile observed anomalies of the recently discovered Higgs-like particle, but also exhibit a vast parameter space, for which the lightest Higgs' phenomenology turns out to be very similar to the Standard Model one. A generic prediction of this model class is the appearance of exotic doubly charged scalar particles. In this paper we adapt existing dilepton+missing energy+jets measurements in the context of SUSY searches to the dominant decay mode $H^{\pm\pm}\to W^\pm W^\pm$ and find that the LHC already starts probing the model's parameter space. A simple modification towards signatures typical of weak boson fusion searches allows us to formulate even tighter constraints with the 7 TeV LHC data set. A corresponding analysis of this channel performed at 14 TeV center of mass energy will constrain the model over the entire parameter space and facilitate potential $H^{\pm\pm}\to W^\pm W^\pm$ discoveries., Comment: typos fixed, references added, matches published version

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 POWHEG method for merging the NLO Higgs plus jet cross-section with the parton shower, and on the MINLO method to simultaneously achieve NLO accuracy for inclusive Higgs boson production. The NNLO accuracy is reached by a reweighting procedure making use of the HNNLO program., Comment: 25 pages, 10 figures. Very minor clarifications in the text for v2

ATLAS and CMS have discovered a Standard Model Higgs-like particle. One of the main discovery channels is the Higgs decay to two photons, which, at the moment, seems to be considerably enhanced over the Standard Model expectation. Models with additional charged matter coupling to the Higgs sector can enhance or decrease the Higgs to two photons branching ratio. We take this as motivation to confront the so-called Georgi-Machacek model of Higgs triplets with the results of recent searches for a SM Higgs boson performed at the LHC. We also investigate the model in regions of the allowed parameter space relevant for a SM-like phenomenology. The Georgi-Machacek model avoids tree-level issues of the T parameter, while offering a vastly modified Higgs phenomenology compared to the Standard Model. This comes at the price of introducing another fine-tuning problem related to electroweak precision measurements. We investigate the collider phenomenology of the Georgi-Machacek model in the light of existing collider constraints beyond any effective field theory approximation and contextualize our findings with electroweak precision constraints., Comment: Added 3 references, reference list reordered, few typos fixed, explanations improved in a couple of places, matches version accepted for publication in PRD

Both the ATLAS and CMS Collaborations have sought for effects beyond pure next-to-leading order in dijet observables, with the goal to distinguish between the perturbative descriptions provided by a next-to-leading order plus collinear-resummation calculation and by the resummation of wide-angle, hard emissions. In this paper we identify regions of phase space in dijet production where some observables receive large corrections beyond next-to-leading order and study their theoretical description with two tools that perform these two different resummations: the POWHEG BOX and HEJ. Furthermore, we suggest analyses where the predictions from POWHEG and HEJ can be clearly distinguished experimentally., Version accepted in PRD

We present results for the QCD production of Z/{\gamma} + 2 jets matched with parton showers using the POWHEG method. Some technicalities relevant for the merging of NLO corrections for this process with parton showers are discussed, and results for typical distributions are shown, in presence of different sets of cuts. A comparison with ATLAS data is also presented, and good agreement is found., Comment: 13+1 pages, 6 figures, 1 reference and 1 appendix added; matches version accepted for publication in JHEP

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., Comment: 16+1 pages, 8 figures, matches version accepted for publication in JHEP

In this article we generalise POWHEG next-to-leading order parton shower (NLOPS) simulations of vector boson production and vector boson production in association with a single jet, to give matrix element corrected MENLOPS simulations. In so doing we extend and provide, for the first time, an exact and faithful implementation of the MENLOPS formalism in hadronic collisions. We also consider merging the resulting event samples according to a phase space partition defined in terms of an effective jet clustering scale. The merging scale is restricted such that the component generated by the associated production simulation does not impact on the NLO accuracy of inclusive vector boson production observables. The dependence of the predictions on the unphysical merging scale is demonstrated. Comparisons with Tevatron and LHC data are presented., Comment: 41 pages, 19 figures. Figures updated from v1.5 to 1.6 of external Rivet program, reference line in figs. 4,5,11 corrected. Citations added, text unchanged

We present an implementation of the next-to-leading order dijet production process in hadronic collisions in the framework of POWHEG, which is a method to implement NLO calculations within a shower Monte Carlo context. In constructing the simulation, we have made use of the POWHEG BOX toolkit, which makes light of many of the most technical steps. The majority of this article is concerned with the study of the predictions of the Monte Carlo simulation. In so doing, we validate our program for use in experimental analyses, elaborating on some of the more subtle features which arise from the interplay of the NLO and resummed components of the calculation. We conclude our presentation by comparing predictions from the simulation against a number of Tevatron and LHC jet-production results., 40 pages, 27 figures

We present an implementation of the next-to-leading order vector boson plus one jet production process in hadronic collision in the framework of POWHEG, which is a method to implement NLO calculations within a Shower Monte Carlo context. All spin correlations in the vector boson decay products have been taken into account. The process has been implemented in the framework of the POWHEG-BOX, an automated computer code for turning a NLO calculation into a shower Monte Carlo program. We present phenomenological results for the case of the Z/gamma plus one jet production process, obtained by matching the POWHEG calculation with the shower performed by PYTHIA, for the LHC, and we compare our results with available Tevatron data., 25 pages, 17 figures

We present a next-to-leading order calculation of single-top production interfaced to Shower Monte Carlo programs, implemented according to the POWHEG method. A detailed comparison with MC@NLO and PYTHIA is carried out for several observables, for the Tevatron and LHC colliders., Comment: Figs. 10, 11 and 12 were obtained without the acceptance cuts described in the text. They have been replaced with the correct ones

We present a next-to-leading order calculation of Higgs boson production via gluon fusion interfaced to shower Monte Carlo programs, implemented according to the POWHEG method. A detailed comparison with MC@NLO and PYTHIA is carried out for several observables, for the Tevatron and LHC colliders. Comparisons with next-to-next-to-leading order results and with resummed ones are also presented., Version accepted for publication by JHEP. One more figure added to Sec 4.1.2 and two more explanatory figures and comments added to Sec 4.3 on p_T distributions

We present a next-to-leading-order calculation of W/Z production interfaced to shower Monte Carlo, implemented according to the POWHEG method. Finite width effects, Z/gamma interference and angular correlations of decay products are included. A detailed comparison with MC@NLO and PYTHIA is carried out., Comment: 35 pages, 34 figures

We present results for the next-to-leading order calculation of single-top Wt-channel production interfaced to Shower Monte Carlo programs, implemented according to the POWHEG method. A comparison with MC@NLO is carried out. Results obtained using the PYTHIA shower are also shown and the effect of typical cuts is briefly discussed., 23 pages, 9 figures

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., 57 pages, 4 figures