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Manuscript Title: Optimal Jet Finder (v1.0 C++)
Authors: S. Chumakov, E. Jankowski, F. V. Tkachov
Program title: Optimal Jet Finder (v1.0 C++)
Catalogue identifier: ADSB_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 175(2006)487
Programming language: C++.
Computer: Any computer with a standard C++ compiler. Tested on,
GNU gcc 3.4.2, Linux Fedora Core 3, Intel i686,
Forte Developer 7 C++ 5.4, SunOS 5.9, UltraSPARC III+,
Microsoft Visual C++ Toolkit 2003 (compiler 13.10.3077, linker 7.10.30777, option /EHsc), Windows XP, Intel i686.
.
Operating system: Tested with, Linux Fedora Core 3, SunOS 5.9, Windows XP.
RAM: ~1 MB (or more, depending on the settings)
Keywords: hadronic jets, jet finding algorithms.
PACS: 13.87.-a, 29.85.+c.
Classification: 11.1, 11.3, 11.9.

Does the new version supersede the previous version?: No, it is an alternative language implementation.

Nature of problem:
Analysis of hadronic final states in high energy particle collision experiments often involves identification of hadronic jets. A large number of hadrons detected in the calorimeter is reduced to a few jets by means of a jet finding algorithm. The jets are used in further analysis which would be difficult or impossible when applied directly to the hadrons. Reference [1] provides brief introduction to the subject of jet finding algorithms and a general review of the physics of jets can be found in [2].

Solution method:
The software we provide is an implementation of the so-called Optimal Jet Definition (OJD). The theory of OJD was developed in [3], [4], [5]. The desired jet configuration is obtained as the one that minimizes Ω, a certain function of the input particles and jet configuration. A FORTRAN 77 implementation of OJD is described in [6].

Restrictions:
Memory required by the program is proportional to the number of particles in the input, times, the number of jets in the output. For example, for 650 particles and 20 jets ~300KB memory is required.

Running time:
The running time (in the running mode with a fixed number of jets) is proportional to the number of particles in the input, times, the number of jets in the output, times, the number of different random initial configurations tried (ntries). For example, for 65 particles in the input and 4 jets in the output, the running time is ~4 x 10-3s per try (Pentium 4 2.8GHz).

References:
[1] D. Yu. Grigoriev, E. Jankowski, F. V. Tkachov, Phys. Rev. Lett. 91, 061801 (2003).
[2] R. Barlow, Rep. Prog. Phys. 36, 1067 (1993).
[3] F. V. Tkachov, Phys. Rev. Lett. 73, 2405 (1994); Erratum, 74, 2618 (1995).
[4] F. V. Tkachov, Int. J. Mod. Phys. A12, 5411 (1997).
[5] F. V. Tkachov, Int. J. Mod. Phys. A17, 2783 (2002).
[6] D. Yu. Grigoriev, E. Jankowski, F. V. Tkachov, Comput. Phys. Commun. 155, 42 (2003).