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 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