New and old jet clustering algorithms for electron-positron events

The Pythia program can be used to generate high-energy-physics 'events', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, with emphasis on those where strong interactions play a rôle, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCDbased models. This physics input is summarized here, for areas such as hard subprocesses, initial-and final-state parton showers, beam remnants and underlying events, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.

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“…A number of different approaches were proposed [Bab80], see review in [Mor98]. Of these, we will here only discuss those based on binary joining.…”

Section: Cluster Findingmentioning

confidence: 99%

PYTHIA 6.4 physics and manual

Sjöstrand

Mrenna

Skands

2006

J. High Energy Phys.

Self Cite

9,615

10,151

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“…Therefore, k T -clustering may be not be the preferred clustering algorithm, and other clustering schemes could be employed (see ref. [38] for an extensive review of clustering schemes and their applicability) that is better suited to a particular event generator. In fact, both programs uses relative p T as a variable in α S .…”

Section: Clusteringmentioning

confidence: 99%

Matching Matrix Elements and Parton Showers with HERWIG and PYTHIA

Mrenna¹,

Richardson²

2004

J. High Energy Phys.

177

236

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Abstract:We report on our exploration of matching matrix element calculations with the parton-shower models contained in the event generators HERWIG and PYTHIA. We describe results for e + e − collisions and for the hadroproduction of W bosons and DrellYan pairs. We compare methods based on (1) a strict implementation of ideas proposed by Catani et al., (2) a generalization based on using the internal Sudakov form factors of HERWIG and PYTHIA, and (3) a simpler proposal of M. Mangano. Where appropriate, we show the dependence on various choices of scales and clustering that do not affect the soft and collinear limits of the predictions, but have phenomenological implications. Finally, we comment on how to use these results to state systematic errors on the theoretical predictions.

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“…The list includes the longitudinally invariant k t algorithm [2,3], the Cambridge/Aachen (C/A) algorithm [4][5][6], the anti-k t algorithm [7], and the Durham algorithm [8], with different features. For details, please also refer to comprehensive reviews [9][10][11][12][13]. All these jet definitions have a pair-wise feature since the criterion whether two jets should be merged into a single one is based on the distance between them.…”

Section: Introductionmentioning

confidence: 99%

The Georgi algorithms of jet clustering

2015

J. High Energ. Phys.

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We reveal the direct link between the jet clustering algorithms recently proposed by Howard Georgi and parton shower kinematics, providing firm foundation from the theoretical side. The kinematics of this class of elegant algorithms is explored systematically for partons with arbitrary masses and the jet function is generalized to J (n) β with a jet function index n in order to achieve more degrees of freedom. Based on three basic requirements that, the result of jet clustering is process-independent and hence logically consistent, for softer subjets the inclusion cone is larger to conform with the fact that parton shower tends to emit softer partons at earlier stage with larger opening angle, and that the cone size cannot be too large in order to avoid mixing up neighbor jets, we derive constraints on the jet function parameter β and index n which are closely related to cone size cutoff. Finally, we discuss how jet function values can be made invariant under Lorentz boost.

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New and old jet clustering algorithms for electron-positron events

Cited by 75 publications

References 56 publications

PYTHIA 6.4 physics and manual

PYTHIA 6.4 physics and manual

Matching Matrix Elements and Parton Showers with HERWIG and PYTHIA

The Georgi algorithms of jet clustering

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