# FF

### A library for evaluating one-loop integrals

FF is a library to evaluate one-loop integrals needed for radiative
corrections to scattering processes in particle physics. The idea of
such a library is based on FormF by M. Veltman. Unfortunately this
only runs in CDC and 68000 assembler,
and uses very high precision (more than 100 digits) to overcome the numerical
instabilities that plague these integrals. FF uses alternative algorithms
which run in double precision Fortran 77. It is available by anonymous ftp.

The current version includes

- The scalar one- to sixpoint functions A0 to F0 for real masses
- Vector functions (using the Passarino-Veltman reduction scheme),
some derived from Andre Aeppli's routines, up to B2,D3,E3,F3
- The A0 to C0 for general complex masses, D0 to F0 in the pole scheme only.

The user interface is described the manual, which is included in the
distribution. The main point to notice is that the routines check their
precision by increasing a parameter **ier**, which should be set to the
number of unreliable digits before calling an ff-routine. One usually
ends up with code like:
ier = 0 ! all digits are OK
id = 3001 ! my threepoint function (optional, choose anything)
call ffxc0(cc0,xpi,ier)
if ( ier.gt.10 ) call ffwarn(998,ier,x0,x0)
! print out why the answer is so bad

There is a coupler to C, C++ and Mathematica available from Würzburg, LoopTools,
this also computes the tensor reduction in their convention.
8-sep-2003: a bug was fixed that gave the wrong value for C11 in very rare circumstances. Please upgrade your library.

Download:

README

ff.tar.gz

ffmanual.ps.gz

Geert Jan van Oldenborgh