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Alexander Mitov

Top++: Computer program for the calculation of the total top-pair cross-section at hadron colliders

  • Program name : Top++
  • Authors : (Aachen) and Alexander Mitov (CERN).
  • Version : 2.0 (it adds the exact NNLO result for g g → tt + X from M. Czakon, P. Fiedler and A. Mitov arXiv:1303.6254 to the previously available NNLO results for qg → tt + X from , qq → tt + X ; qqbar' → tt + X ; qq' → tt + X from and qqbar → tt + X from ).
  • Programing language : C++.
  • Download : Go to downloads page .
  • Installation instructions and manual : can be found inside the distributed software; see also below.
  • Purpose : The program calculates the total inclusive cross-section for top-pair production at hadron colliders like the Tevatron and LHC. The program is capable of calculating the cross-section in fixed order QCD with exact NNLO. The program can also perform full NNLL soft gluon resummation. The resummation is done in Mellin space and then inverted numerically to x-space via the so-called Minimal Prescription.
  • Software expertise needed to operate the program : None. Once the program has been installed (which itself is trivial; you can ask a colleague or your system administrator for help) the only point of interaction with the program is the text file top++.cfg . This file can be edited with a text editor, then saved, followed by typing the command ./top++ to execute the program.
  • Functionality : The program offers a large number of settings. The default setting corresponds to the best prediction of the paper by M. Czakon, P. Fiedler and A. Mitov arXiv:1303.6254 and also by M. Cacciari, M. Czakon, M. Mangano, A. Mitov and P. Nason , . The user can choose between fixed order calculation and a resummed one matched to a given perturbative order (up to NNLO+NNLL). For a discussion of the various options and a comparison between them (and how to interpret the differences) see the article mentioned above.
  • Dependencies : The program requires two standard external libraries:
  1. GSL (GNU scientific library) It provides one dimensional integration routines and few special functions.
  2. LHAPDF : the Les Houches parton densities library.
  • Installation : unarchive the program in a convenient directory. Then specify the C++ compiler and paths to libraries (if non-standard) inside the file makefile . Then type make . Finally type the command ./top++ The output will appear on the screen and inside the output file top++.res . The program has been tested with the GCC (GNU compiler collection) C++ compiler on a Linux and Mac OSX (10.6) platforms.
  • Program settings : The program comes with a default set of settings corresponding to the best prediction of M. Czakon, P. Fiedler and A. Mitov arXiv:1303.6254 . To override any of the default options one has to type the desired option, and its value, in the file top++.cfg . After the file has been modified, it needs to be saved and then the program executed as usual. Please note that the file top++.cfg represents the only point of contact between the user and the program, i.e. unless the user wishes to modify the program itself, he/she will not need to ever open another file besides top++.cfg . If any other file has been edited/modified (to modify the default settings located in the file top++.cpp for example), one has to first type make and then execute the program again, as described above.
  • Questions/Comments/Suggestions : The authors would appreciate any comments, suggestions or questions you might have. We can be contacted here .
  • Acknowledgements : The authors would like to thank Matteo Cacciari, Michelangelo Mangano and Paolo Nason for numerous cross-checks and a very fruitful collaboration that led to the creation of this software. We also thank Juan Rojo, Graeme Watt and Malgorzata Worek for useful suggestions.
Last Updated ( Tuesday, 26 March 2013 10:18 )