A fortran-library for one-loop integrals

We introduce the fortran-library COLLIER for the numerical evaluation of one-loop scalar and ten-sor integrals in perturbative relativistic quantum field theories. Important features are the imple-mentation of dedicated methods to achieve numerical stability for 3- and 4-point tensor integrals, the support of complex masses for internal particles, and the possibility to choose between di-mensional and mass regularization for infrared singularities. COLLIER supports one-loop N-point functions up to currently N = 6 and has been tested in various NLO QCD and EW calculations