GR@PPA 2.7 event generator for pp/pp¯ collisions

The GR@PPA event generator has been updated to version 2.7. This distribution provides event generators for V (W or Z) + jets (⩽4 jets), VV+jetsVV+jets (⩽2 jets) and QCD multi-jet (⩽4 jets) production processes at pp   and pp¯ collisions, in addition to the four bottom quark productions implemented in our previous work (GR@PPA_4b). Also included are the top-pair and top-pair + jet production processes, where the correlation between the decay products are fully reproduced at the tree level. Namely, processes up to seven-body productions can be simulated, based on ordinary Feynman diagram calculations at the tree level. In this version, the GR@PPA framework and the process dependent matrix-element routines are separately provided. This makes it easier to add further new processes, and allows users to make a choice of processes to implement. This version also has several new features to handle complicated multi-body production processes. A systematic way to combine many subprocesses to a single base-subprocess has been introduced, and a new method has been adopted to calculate the color factors of complicated QCD processes. They speed up the calculation significantly.Program summaryTitle of program:GR@PPA (v2.7)Catalogue identifier:ADRH_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADRH_v2_0Program obtainable from: CPC Program Library, Queen's University of Belfast, N. IrelandOperating system under which the program has been tested:UNIXProgramming language used:Fortran77Other CPC library programs required:PYTHIA, HERWIG, BASES, SPRINGMemory required to execute with typical data:56.5 kwords for an integration, 74.6 kwords for an event generationNumber of bytes in distributed program, including test data, etc.: 570 587No. of lines in distributed program, including test data, etc.:143 327Distribution format:tar.gzNature of physical problem:The multi-legs interaction processes have become more important with increasing the colliding energy available at the high energy collider experiments. At hadron-collider experiments, since thousands of Feynman diagrams contributes in the single interaction process, the faster and more stable calculation to obtain the results is desirable.Method of solution: GR@PPA is an event generator for V (W or Z) + jets (⩽ 4 jets), VV+jetsVV+jets (⩽ 2 jets) and QCD multi-jet (⩽ 4 jets) production processes at pp   and pp¯ collisions, in addition to the four bottom quark productions implemented in our previous work (GR@PPA_4b). Also included are the top-pair and top-pair + jet production processes. In this version, the GR@PPA framework and the process dependent matrix-element routines are separately provided. This makes it easier to add further new processes, and allows users to make a choice of processes to implement. This version also has several new features to handle complicated multi-body production processes. A systematic way to combine many subprocesses to a single base-subprocess has been introduced, and a new method has been adopted to calculate the color factors of complicated QCD processes. They speed up the calculation significantly.Restrictions on the complexity of the program: The interference between decay fermions from the boson and those from other sources is ignored in the diagram calculation.Typical running time: 2 hours for a cross-section integration and 200 msec per 1 event for an event generation.