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Manuscript Title: BOKASUN: a fast and precise numerical program to calculate the Master Integrals of the two-loop sunrise diagrams
Authors: Michele Caffo, Henryk Czyz, Michal Gunia, Ettore Remiddi
Program title: BOKASUN
Catalogue identifier: AECG_v1_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 180(2009)427
Programming language: FORTRAN77.
Computer: Any computer with a Fortran compiler accepting FORTRAN77 standard. Tested on various PC's with LINUX.
Operating system: LINUX.
RAM: 120 kbytes
Keywords: Feynman diagrams, sunrise diagram, numerical evaluation.
PACS: 11.15.Bt.
Classification: 4.4.

Nature of problem:
Any integral arising in the evaluation of the two-loop sunrise Feynman diagram can be expressed in terms of a given set of Master Integrals, which should be calculated numerically. The program provides a fast and precise evaluation method of the Master Integrals for arbitrary (but not vanishing) masses and arbitrary value of the external momentum.

Solution method:
The integrals depend on three internal masses and the external momentum squared p2. The method is a combination of an accelerated expansion in 1/p2 in its (pretty large!) region of fast convergence and of a Runge-Kutta numerical solution of a system of linear differential equations.

Running time:
To obtain 4 Master Integrals on PC with 2 GHz processor it takes 3 μs for series expansion with pre-calculated coefficients, 80 μs for series expansion without pre-calculated coefficients, from a few seconds up to a few minutes for Runge-Kutta method (depending on the required accuracy and the values of the physical parameters).