Optimal Jet Finder (v1.0 C++)

Abstract

We describe a C++ implementation of the Optimal Jet Definition for identification of jets in hadronic final states of particle collisions. We explain interface subroutines and provide a usage example. The source code is available from http://www.inr.ac.ru/~ftkachov/projects/jets/. Program summary Title of program: Optimal Jet Finder (v1.0 C++) Catalogue identifier: ADSB_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADSB_v2_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: any computer with a standard C++ compiler Tested with: (1) GNU gcc 3.4.2, Linux Fedora Core 3, Intel i686; (2) Forte Developer 7 C++ 5.4, SunOS 5.9, UltraSPARC III+; (3) Microsoft Visual C++ Toolkit 2003 (compiler 13.10.3077, linker 7.10.30777, option /EHsc), Windows XP, Intel i686. Programming language used: C++ Memory required: ∼ 1 MB (or more, depending on the settings) No. of lines in distributed program, including test data, etc.: 3047 No. of bytes in distributed program, including test data, etc.: 17 884 Distribution format: tar.gz Nature of physical 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. Grigoriev et al. [D.Yu. Grigoriev, E. Jankowski, F.V. Tkachov, Phys. Rev. Lett. 91 (2003) 061801] provide brief introduction to the subject of jet finding algorithms and a general review of the physics of jets can be found in [R. Barlow, Rep. Prog. Phys. 36 (1993) 1067]. Method of solution: The software we provide is an implementation of the so-called Optimal Jet Definition (OJD). The theory of OJD was developed in [F.V. Tkachov, Phys. Rev. Lett. 73 (1994) 2405; Erratum, Phys. Rev. Lett. 74 (1995) 2618; F.V. Tkachov, Int. J. Modern Phys. A 12 (1997) 5411; F.V. Tkachov, Int. J. Modern Phys. A 17 (2002) 2783]. 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 [D.Yu. Grigoriev, E. Jankowski, F.V. Tkachov, Comput. Phys. Comm. 155 (2003) 42]. Restrictions on the complexity of the program: Memory required by the program is proportional to the number of particles in the input × the number of jets in the output. For example, for 650 particles and 20 jets ∼ 300 KB memory is required. Typical 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 × 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 ⋅ 10 −3 s per try (Pentium 4 2.8 GHz).