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Unformatted text preview: 35. Monte Carlo particle numbering scheme 1 35. MONTE CARLO PARTICLE NUMBERING SCHEME Revised November 2009 by L. Garren (Fermilab), C.-J. Lin (LBNL), S. Navas (U. Granada), P. Richardson (Durham U.), T. Sj ostrand (Lund U.), and T. Trippe (LBNL). The Monte Carlo particle numbering scheme presented here is intended to facilitate interfacing between event generators, detector simulators, and analysis packages used in particle physics. The numbering scheme was introduced in 1988  and a revised version [2,3] was adopted in 1998 in order to allow systematic inclusion of quark model states which are as yet undiscovered and hypothetical particles such as SUSY particles. The numbering scheme is used in several event generators, e.g. HERWIG, PYTHIA, and SHERPA, and interfaces, e.g. /HEPEVT/ and HepMC. The general form is a 7digit number: n n r n L n q 1 n q 2 n q 3 n J . This encodes information about the particles spin, avor content, and internal quantum numbers. The details are as follows: 1. Particles are given positive numbers, antiparticles negative numbers. The PDG convention for mesons is used, so that K + and B + are particles. 2. Quarks and leptons are numbered consecutively starting from 1 and 11 respectively; to do this they are first ordered by family and within families by weak isospin. 3. In composite quark systems (diquarks, mesons, and baryons) n q 1 3 are quark numbers used to specify the quark content, while the rightmost digit n J = 2 J + 1 gives the systems spin (except for the K S and K L ). The scheme does not cover particles of spin J > 4. 4. Diquarks have 4-digit numbers with n q 1 n q 2 and n q 3 = 0. 5. The numbering of mesons is guided by the nonrelativistic ( L S decoupled) quark model, as listed in Tables 14.2 and 14.3. a. The numbers specifying the mesons quark content conform to the convention n q 1 = 0 and n q 2 n q 3 . The special case K L is the sole exception to this rule. b. The quark numbers of avorless, light ( u, d, s ) mesons are: 11 for the member of the isotriplet ( , , . . . ), 22 for the lighter isosinglet ( , , . . . ), and 33 for the heavier isosinglet ( , , . . . ). Since isosinglet mesons are often large mixtures of u u + d d and s s states, 22 and 33 are assigned by mass and do not necessarily specify the dominant quark composition. c. The special numbers 310 and 130 are given to the K S and K L respectively. d. The fifth digit n L is reserved to distinguish mesons of the same total ( J ) but different spin ( S ) and orbital ( L ) angular momentum quantum numbers. For J > 0 the numbers are: ( L, S ) = ( J 1 , 1) n L = 0 , ( J, 0) n L = 1 , ( J, 1) n L = 2 and ( J + 1 , 1) n L = 3. For the exceptional case J = 0 the numbers are (0 , 0) n L = 0 and (1 , 1) n L = 1 ( i.e. n L = L )....
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This note was uploaded on 06/07/2011 for the course PHYS 4132 taught by Professor Kutter during the Spring '11 term at University of Florida.
- Spring '11