Program title: MCgrid
Catalogue identifier: AESS_v2_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AESS_v2_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html
No. of lines in distributed program, including test data, etc.: 512334
No. of bytes in distributed program, including test data, etc.: 4263504
Distribution format: tar.gz
Programming language: C++, shell, Python.
Computer: PC running Linux, Mac.
Operating system: Linux, Mac OS.
RAM: Varying
70">Catalogue identifier of previous version: AESS_v1_0
Journal reference of previous version: Comput. Phys. Comm. 185(2014)2115
Classification: 11.2, 11.5, 11.9.
External routines: HepMC [1], Rivet [2], APPLgrid [3] and fastNLO [4]. A SHERPA [5] installation is also required.
Does the new version supersede the previous version?: Yes
Nature of problem: Efficient filling of cross section grid files from fully exclusive parton level Monte Carlo events.
Solution method: Analyse Monte Carlo events via the Rivet program, which projects events on discretized cross section tables from APPLgrid [3] or fastNLO [4].
Reasons for new version:
Previous MCgrid releases, cf. [6], supported only a single interpolation tool: APPLgrid [3]. Interfacing to more than one is important for cross checks and allows the use of MCgrid in a wider range of existing workflows.
The recently released SHERPA 2.2.0 provides more information in the HepMC [1] event record, allowing for the filling of the exact next-to-leading-order expansion of an MC@NLO calculation, see e.g. [7] for details, into an interpolation grid. To process the additional information and adopt the new weight naming convention used in SHERPA 2.2.0, modifications on the MCgrid side have been necessary. The possibility of filling grids for MC@NLO-type calculations broadens the scope of MCgrid. It allows for the quantification of the residual dependencies on the parton showers that are beyond the fixed-order approximation. Understanding these dependencies and eventually taking them into account during the creation of interpolation grids in an automated way would help in the fitting of PDFs to data that are not appropriately described by fixed-order calculations.
As an additional interpolation tool fastNLO [4] is now supported. This is the first time the fastNLO package can be used in conjunction with a multi-purpose Monte Carlo event generator. The required version of the fastNLO toolkit [8] is 2.3.1pre-2125 or later. With APPLgrid and fastNLO, all currently available interpolation tools for fixed-order QCD cross sections can now be used in conjunction with MCgrid.
Modifications have been made in order to adopt the new naming conventions in the HepMC event record format introduced in SHERPA 2.2.0.
The filling of the exact next-to-leading-order expansion of MC@NLO calculations has been implemented. The required information must be provided with the HepMC event record, which is the case for SHERPA 2.2.0.
The MCgrid::BinnedGrid class has been added. It corresponds to the Rivet::BinnedHistogram class and allows for the direct creation of grids for every Rivet histogram combined therein.
MCGRID_OUTPUT_PATH has been introduced, an environmental variable for specifying the grid output directory.
An automatic counter suffix for grid file names has been added to prevent overwriting.
The API has been streamlined for easier enabling of Rivet analyses for MCgrid.
The provided examples have been updated for use with SHERPA 2.2.0 and Rivet 2.2.1.
References:
M. Dobbs, J. B. Hansen, The HepMC C++ Monte Carlo event record for High Energy Physics, Comput. Phys. Commun. 134 (2001) 41-46. http://dx.doi.org/10.1016/S0010-4655(00)00189-2.
A. Buckley, J. Butterworth, L. Lönnblad, D. Grellscheid, H. Hoeth, et al., Rivet user manual, Comput. Phys. Commun. 184 (2013) 2803-2819. arXiv:1003.0694,http://dx.doi.org/10.1016/j.cpc.2013.05.021.
T. Carli, D. Clements, A. Cooper-Sarkar, C. Gwenlan, G. P Salam, et al., A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project, Eur. Phys. J. C66 (2010) 503-524. arXiv:0911.2985, http://dx.doi.org/10.1140/epjc/s10052-010-1255-0.
70">T. Kluge, K. Rabbertz, M. Wobisch, FastNLO: Fast pQCD calculations for PDF fits (2006) 483-486. arXiv:hep-ph/0609285.
T. Gleisberg, S. Höche, F. Krauss, M. Schönherr, S. Schumann, et al., Event generation with SHERPA 1.1, JHEP 0902 (2009) 007. arXiv:0811.4622, 708/2009/02/007">http://dx.doi.org/10.1088/1126-6708/2009/02/007.
L. Del Debbio, N. P Hartland, S. Schumann, MCgrid: projecting cross section calculations on grids, Comput.Phys.Commun. 185 (2014) 2115-2126. arXiv:1312.4460, http://dx.doi.org/10.1016/j.cpc.2014.03.023.
S. Höche, F. Krauss, M. Schönherr, F. Siegert, A critical appraisal of NLO+PS matching methods, JHEP 1209 (2012) 049. arXiv:1111.1220, 70" class="interref" data-locatorType="url" data-locatorKey="http://dx.doi.org/10.1007/JHEP09(2012)049">http://dx.doi.org/10.1007/JHEP09(2012)049.
D. Britzger, K. Rabbertz, F. Stober, M. Wobisch, New features in version 2 of the fastNLO project (2012) 217-221. arXiv:1208.3641, http://dx.doi.org/10.3204/DESY-PROC-2012-02/165.