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[Licence| Download | New Version Template] aeeo_v2_0.tar.gz(928 Kbytes)
Manuscript Title: Golem95C: A library for one-loop integrals with complex masses
Authors: G. Cullen, J.-Ph. Guillet, G. Heinrich, T. Kleinschmidt, E. Pilon, T. Reiter, M. Rodgers
Program title: golem95-1.2.0
Catalogue identifier: AEEO_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 182(2011)2276
Programming language: Fortran95.
Computer: Any computer with a Fortran95 compiler.
Operating system: Linux, Unix.
RAM: RAM used per integral/form factor is insignificant
Keywords: NLO computations, One-loop diagrams, Complex masses, Unstable particles.
PACS: 12.38.Bx.
Classification: 4.4, 11.1.

External routines: Some finite scalar integrals are called from OneLOop [1,2], the option to call them from LoopTools [3,4] is also implemented.

Does the new version supersede the previous version?: Yes

Nature of problem:
Evaluation of one-loop multi-leg integrals occurring in the calculation of next-to-leading order corrections to scattering amplitudes in elementary particle physics. In the presence of massive particles in the loop, propagators going on-shell can cause singularities which should be regulated to allow for a successful evaluation.

Solution method:
Complex masses can be used in the loop integrals to stand for a width of an unstable particle, regulating the singularities by moving the poles away from the real axis.

Reasons for new version:
The previous version was restricted to massless particles in the loop.

Summary of revisions:
Real and complex masses are supported, a general μ parameter for the renormalisation scale is introduced, improvements in the caching system and the user interface.

Running time:
Depends on the nature of the problem. A single call to a rank 6 six-point form factor at a randomly chosen kinematic point, using complex masses, takes 0.06 seconds on an Intel Core 2 Q9450 2.66GHz processor.

References:
[1] A. van Hameren, C. G. Papadopoulos, and R. Pittau, Automated one-loop calculations: a proof of concept, JHEP 09 (2009) 106, [arXiv:0903.4665].
[2] A. van Hameren, OneLOop: for the evaluation of one-loop scalar functions, [arXiv:1007.4716].
[3] T. Hahn and M. Perez-Victoria, Automatized one-loop calculations in four and D dimensions, Comput. Phys. Commun. 118 (1999) 153-165, [hep-ph/9807565].
[4] T. Hahn, Feynman Diagram Calculations with FeynArts, FormCalc, and LoopTools, [arXiv:1006.2231].