openloops is hosted by Hepforge, IPPP Durham


OpenLoops 2


About The OpenLoops 2 program is a fully automated implementation of the Open Loops algorithm combined with on-the-fly reduction methods, which allows for the fast and stable numerical evaluation of tree and one-loop matrix elements for any Standard Model process at NLO QCD and NLO EW.

On this website you find the latest version of OpenLoops with installation instructions and a documentation of the most important features, input parameters, and available Fortran90 and C/C++ interfaces.

This webpage is still under construction and will be updated regularly. A reference manual will become available soon.

Cite When OpenLoops 2 is used for a publication please cite:

F. Buccioni, J.-N. Lang, J.M. Lindert, P. Maierhöfer, S. Pozzorini, H. Zhang, M. Zoller
Eur.Phys.J. C79 (2019) no.10, 866

as well as the third party tools used for scalar integrals and reduction of loop-squared amplitudes.

Additionally depending on the application the following papers desrcibing the underlying algorithms should be cited:

F. Cascioli, P. Maierhöfer and S. Pozzorini,
Phys. Rev. Lett. 108 (2012) 111601

F. Buccioni, S. Pozzorini, M. Zoller
Eur.Phys.J. C78 (2018) no.1, 70

S. Kallweit, J. M. Lindert, P. Maierhöfer and S. Pozzorini, M. Schönherr
JHEP 1504 (2015) 012

Contact please send comments and bug reports to and subscribe to our mailing list to keep updated.