AcerMC Monte-Carlo Generator

Borut Paul Kersevan1 and Elzbieta Richter-Was2

1 Jozef Stefan Institute
,Jamova 39,SI-1000 Ljubljana,Slovenia;
Faculty of Mathematics and Physics, University of Ljubljana,
Jadranska 19,SI-1000 Ljubljana,Slovenia
2 Institute of Pyhsics, Jagiellonian University
,30-075 Krakow, Reymonta 4, Poland
Institute of Nuclear Physics - Polish Academy of Science
,31-342 Krakow, Radzikowskiego 152, Poland


  • The AcerMC Monte-Carlo event generator is dedicated for generation of the Standard Model background processes in pp collisions at the LHC. The program itself provides a FORTRAN library of the massive matrix elements and phase space modules for generation of a set of selected processes. The hard process events, generated with one of these modules, can be completed by the initial and final state radiation, hadronisation and decays, simulated with either PYTHIA 6.4, ARIADNE 4.1 or HERWIG 6.5 Monte-Carlo event generators. Interfaces to both generators are provided in the distribution. The matrix elements have been coded by the MadGraph/HELAS package. The phase-space generation is based on the multi-channel self-optimising approach using the modified Kajantie-Byckling formalism for phase space construction and further smoothing of the phase space was obtained by using a modified ac-VEGAS algorithm. Please see the manual for details.

Implemented processes

  • There are currently 25 implemented processes.
  • And the additional 'control' processes for cross-checks:


Source Code



  • AcerDET - a package for fast detector simulation and reconstruction can be found here


  • 2.5.2011 the AcerMC version 3.8 is released. New ATLAS defaults are added as the running options.

  • 22.6.2009 the AcerMC version 3.7 is released. An improvement for top pair processes is made because due to numerical accuracy the branching ratios in top pair decays were off by a few percent when using the non-full-hadronic branching mode (ACSET13=6) which is now corrected.

  • 14.12.2008 the AcerMC version 3.6 is released. A bug fix for top pair processes is made because the angular distributions in W+ decays for quark initial state (process 12) were reversed. The bug was introduced in AcerMC 3.2.

  • 15.4.2008 the AcerMC version 3.5 is released. The processes 26 is added, describing massive PS+ME procedure in the case of g g -> Z b b~ production. The process 27 combines this one with process 6. There are new switches ACSET(60-61) which set the polarisation in hadronic and leptonic top pair decays as described in the manual and acermc.card.

  • 11.9.2006 the AcerMC version 3.4 is released. The processes 24 and 25 combining the processes 24=5+6 and 25=7+8 were added for convenience.

  • 20.7.2006 the AcerMC version 3.3 is released. A bugfix for process 18 (wrong subprocesses called when selecting it) and general code cleanup.

  • 15.7.2006 A bugfix (thanks to Jean-Baptiste Devivie) in the AcerMC version 3.2 . The issue was that in Wbb and Wtt processes 3 and 4 the W charge was reversed by a modification in code introduced in the 3.x versions. The source tarball for 3.2 has been replaced. No other processes were affected.

  • 23.6.2006 The AcerMC version 3.2 is released. There are several new options for top pair decays and Z-prime models. Also, a typo in the manual which listed the tttt cross-sections as an order of magnitude (factor 10) too big was corrected. Please consult the manual for details.

  • 18.2.2006 The AcerMC version 3.1 is released.There are several new processes (single top production, associated Z b production, Z-prime production etc. as well as the new for (ISR) parton shower and matrix element matching procedure for the processes involving a b-quark in the initial state. Please consult the manual for details.

  • 21.3.2005 The AcerMC version 2.4 is released. This version implements the LHAPDF/LHAGLUE interface which replaces the obsolete PDFLIB804 libraries.

  • 31.10.2004 The AcerMC version 2.3 is released. This version contains a new ACSET(13)=17 setting which enables one to produce final states in processes 11-14 where both bosons decay leptonically to either electron or muon (+ neutrinos).

  • 27.9.2004 The AcerMC version 2.2 is released. This version contains a simple bug fix related to the charge of the reconstructed W bosons in the history of processes 11-14; there used to be a charge assignment error in about 2 percent of cases, the bug was in event history only, the final state was correct. Thanks to Jean-Baptiste Devivie and Pascal Pralavorio for pointing this out.

  • 23.6.2004 The AcerMC version 2.1 is released. This version contains the new interface to ARIADNE 4.12, the use is analogous to running PYTHIA/HERWIG (just type 'make run_ar'). The latest PYTHIA 6.224 and HERWIG 6.505 versions have been included. For details please consult the updated manual and the provided INSTALL file.

  • 25.5.2005 The AcerMC version 2.0 is released. This version contains a completely re-done phase space sampling algorithms which now provide 6 and more particles in the final state. Several new processess have been implemented at user requests. Please consult the updated manual for details.

  • 18.6.2003 The hwmodk.f file in the AcerMC version 1.4 distribution got corrupted during the tar process; the distribution is now replaced with an uncorrupted file. The PYTHIA interface was not affected. We thank Z. Was for pointing this out and apologise for possible inconvenience.

  • 10.5.2003 The AcerMC version 1.4 is released. The interfaces to external TAUOLA and PHOTOS libraries were added. The necessary modifications in the interface routines and the native PHOTOS code were made to enable the user to process the events with TAUOLA and/or PHOTOS using PYTHIA or HERWIG as the supervising generators. The interfaces to external TAUOLA and

  • 10.2.2003 The AcerMC version 1.3 is released. A transition to the HERWIG 6.5 was made, which now supports the Les Houches standard for handling the external processes. Consequently, the AcerMC interface to HERWIG 6.5 was completely rewritten. As a direct consequence, the same event record can freely be swapped (i.e. read back) to either PYTHIA or HERWIG for fragmentation and hadronisation treatment. In addition, the PYTHIA version was upgraded to PYTHIA 6.214. Furthermore, the build procedure of the libraries and executables was greatly simplified. For details please consult the updated manual and the provided INSTALL file.

  • 20.9.2002 The AcerMC version 1.2 is released. The changes include a bug fix in HERWIG 6.4, transition to PYTHIA 6.208 and the implementation of storing/reading back of hard process events according to the Les Hauches standard (the implementation is simplified with respect to version 1.1). For details please consult the updated manual and the provided INSTALL file.

  • 11.7.2002 The AcerMC version 1.1 is released. The changes include transition to HERWIG 6.4, updated scale choices for processes 5-8, inclusion of control processes 91-94 for consistent evaluations and a possibility of an event dump according to the Les Hauches standard. For details please consult the updated manual and the provided INSTALL file.

  • 7.6.2002 The AcerMC writeup was updated according to suggestions given by the CPC referee. Also, in the code a bug-fix was made: AcerMC incorrectly copied the CKM matrix from the Pythia/Herwig interface, resulting in the total cross-sections for processes 3 and 4 being about 10% too low (kinematic distributions of events were not affected); this is nevertheless still well within the theoretical uncertaintly on the values. Please consult the updated writeup for new numbers.

  • 5.3.2002 For additional information about AcerMC capabilities, the transparencies of the talk given at the CERN Theory Division seminar on particle physics phenomenology on 1.3.2002 are given here .

  • 1.2.2002 First release, version 1.0. The code has been thoroughly checked but please still consider the release to be to some extent ' beta ', some bugs are probably still there. When in doubt you are incouraged to contact the authors.