GR@PPA 2.7 event generator for pp/p(p)over-bar 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), V V +jets (<= 2 jets) and QCD multi-jet (<= 4 jets) production processes at pp, and p (p) over bar 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.
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