Eur. Phys. J. C (2013) 73: 2608
https://doi.org/10.1140/epjc/s10052-013-2608-2

Special Article - Tools for Experiment and Theory

Fast computation of MadGraph amplitudes on graphics processing unit (GPU)

¹ KEK Theory Center and Sokendai, Tsukuba, 305-0801, Japan
² KEK and Sokendai, Tsukuba, 305-0801, Japan
³ Department of Physics and State Key, Laboratory of Nuclear Physics and Technology, Peking University, Beijing, 100871, China
⁴ Department of Radiological Sciences, International University of Health and Welfare, Kitakenamaru, 2600-1, Ohtawara, Tochigi, Japan
⁵ Department of Physics, University of Illinois, Urbana, IL, 61801, USA

^* e-mail: junichi.kanzaki@kek.jp

Received: 3 May 2013
Revised: 6 September 2013
Published online: 5 November 2013

Abstract

Continuing our previous studies on QED and QCD processes, we use the graphics processing unit (GPU) for fast calculations of helicity amplitudes for general Standard Model (SM) processes. Additional HEGET codes to handle all SM interactions are introduced, as well as the program MG2CUDA that converts arbitrary MadGraph generated HELAS amplitudes (FORTRAN) into HEGET codes in CUDA. We test all the codes by comparing amplitudes and cross sections for multi-jet processes at the LHC associated with production of single and double weak bosons, a top-quark pair, Higgs boson plus a weak boson or a top-quark pair, and multiple Higgs bosons via weak-boson fusion, where all the heavy particles are allowed to decay into light quarks and leptons with full spin correlations. All the helicity amplitudes computed by HEGET are found to agree with those computed by HELAS within the expected numerical accuracy, and the cross sections obtained by gBASES, a GPU version of the Monte Carlo integration program, agree with those obtained by BASES (FORTRAN), as well as those obtained by MadGraph. The performance of GPU was over a factor of 10 faster than CPU for all processes except those with the highest number of jets.