The anti-$k_t$ jet clustering algorithm
TL;DR: The anti-k-t algorithm as mentioned in this paper behaves like an idealised cone algorithm, in that jets with only soft fragmentation are conical, active and passive areas are equal, the area anomalous dimensions are zero, the non-global logarithms are those of a rigid boundary and the Milan factor is universal.
Abstract: The k_t and Cambridge/Aachen inclusive jet finding algorithms for hadron-hadron collisions can be seen as belonging to a broader class of sequential recombination jet algorithms, parametrised by the power of the energy scale in the distance measure. We examine some properties of a new member of this class, for which the power is negative. This ``anti-k_t'' algorithm essentially behaves like an idealised cone algorithm, in that jets with only soft fragmentation are conical, active and passive areas are equal, the area anomalous dimensions are zero, the non-global logarithms are those of a rigid boundary and the Milan factor is universal. None of these properties hold for existing sequential recombination algorithms, nor for cone algorithms with split--merge steps, such as SISCone. They are however the identifying characteristics of the collinear unsafe plain ``iterative cone'' algorithm, for which the anti-k_t algorithm provides a natural, fast, infrared and collinear safe replacement.
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Abstract: We discuss the theoretical bases that underpin the automation of the computations of tree-level and next-to-leading order cross sections, of their matching to parton shower simulations, and of the merging of matched samples that differ by light-parton multiplicities. We present a computer program, MadGraph5 aMC@NLO, capable of handling all these computations — parton-level fixed order, shower-matched, merged — in a unified framework whose defining features are flexibility, high level of parallelisation, and human intervention limited to input physics quantities. We demonstrate the potential of the program by presenting selected phenomenological applications relevant to the LHC and to a 1-TeV e + e − collider. While next-to-leading order results are restricted to QCD corrections to SM processes in the first public version, we show that from the user viewpoint no changes have to be expected in the case of corrections due to any given renormalisable Lagrangian, and that the implementation of these are well under way.
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TL;DR: FastJet as mentioned in this paper is a C++ package that provides a broad range of jet finding and analysis tools, including efficient native implementations of all widely used 2→1 sequential recombination jet algorithms for pp and e − − collisions.
Abstract: FastJet is a C++ package that provides a broad range of jet finding and analysis tools. It includes efficient native implementations of all widely used 2→1 sequential recombination jet algorithms for pp and e
+
e
− collisions, as well as access to 3rd party jet algorithms through a plugin mechanism, including all currently used cone algorithms. FastJet also provides means to facilitate the manipulation of jet substructure, including some common boosted heavy-object taggers, as well as tools for estimation of pileup and underlying-event noise levels, determination of jet areas and subtraction or suppression of noise in jets.
3,713 citations
TL;DR: Delphes as mentioned in this paper is a fast-simulation of a multipurpose detector for phenomenological studies, including a track propagation system embedded in a magnetic field, electromagnetic and hadron calorimeters, and a muon identification system.
Abstract: The version 3.0 of the Delphes fast-simulation is presented. The goal of Delphes is to allow the simulation of a multipurpose detector for phenomenological studies. The simulation includes a track propagation system embedded in a magnetic field, electromagnetic and hadron calorimeters, and a muon identification system. Physics objects that can be used for data analysis are then reconstructed from the simulated detector response. These include tracks and calorimeter deposits and high level objects such as isolated electrons, jets, taus, and missing energy. The new modular approach allows for greater flexibility in the design of the simulation and reconstruction sequence. New features such as the particle-flow reconstruction approach, crucial in the first years of the LHC, and pile-up simulation and mitigation, which is needed for the simulation of the LHC detectors in the near future, have also been implemented. The Delphes framework is not meant to be used for advanced detector studies, for which more accurate tools are needed. Although some aspects of Delphes are hadron collider specific, it is flexible enough to be adapted to the needs of electron-positron collider experiments.
2,692 citations
References
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TL;DR: Pythia and JETSET as discussed by the authors are two main components of the “Lund Monte Carlo” program suite, and they can be used to generate high-energy-physics "events".
2,109 citations
TL;DR: Pythia version 6 represents a merger of the Pythia 5, Jetset 7 and SPythia programs, with many improvements as discussed by the authors, which can be used to generate high-energy physics events.
1,723 citations
TL;DR: In this article, it was shown that the complexity of k t jet clustering can be reduced to two-dimensional nearest neighbor location for a dynamic set of points, which can then be performed in N ln N time.
1,565 citations
TL;DR: It is suggested that a successive combination style algorithm, similar to that used in [ital e][sup +][ital e[minus]] physics, might be useful also in hadron collisions, where cone style algorithms have been used previously.
Abstract: Jet finding algorithms, as they are used in ${e}^{+}{e}^{\ensuremath{-}}$ and hadron collisions, are reviewed and compared. It is suggested that a successive combination style algorithm, similar to that used in ${e}^{+}{e}^{\ensuremath{-}}$ physics, might be useful also in hadron collisions, where cone style algorithms have been used previously.
1,211 citations
TL;DR: In this article, a version of the QCD-motivated "k⊥" jet-clustering algorithm for hadron-hadron collisions is proposed, which is invariant under boosts along the beam directions.
1,130 citations