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

Quick links:

  • Versions and Downloads (latest version 2.0).
  • Tips for installing Top++ on Mac OS X
  • Tips for plotting the results of the program Top++


Detailed information:

  • Program name: Top++
  • Authors: Michal Czakon (Aachen) and Alexander Mitov (Cambridge).
  • Version: 2.0 . This version contains all partonic reactions at NNLO. (Specifically, it adds the exact NNLO result for gg → tt + X from M. Czakon, P. Fiedler and A. Mitov arXiv:1303.6254 to the previously available NNLO results for qg → tt + X from M.Czakon and A. Mitov arXiv:1210.6832, qq → tt + X ; qqbar’ → tt + X ; qq’ → tt + X from M. Czakon and A. Mitov, arXiv:1207.0236 and qqbar → tt + X from P. Bernreuther, M. Czakon and A. Mitov arXiv:1204.5201).
  • Programming language: C++.
  • 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, arXiv:1111.5869 [hep-ph]. 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 on the project that led to the creation of this software. We also thank Juan Rojo, Graeme Watt and Malgorzata Worek for useful suggestions.
  • Disclaimer: All software on this web-page is available for your use. You can use is as is, or modify it for your own applications. In such case please acknowledge this. The authors of the software made available on this web-site do not give or imply any warranty that the software works. It has been, however, extensively tested and we believe it to be correct.