Collier: A fortran-based complex one-loop library in extended regularizations

Abstract We present the library Collier  for the numerical evaluation of one-loop scalar and tensor integrals in perturbative relativistic quantum field theories. The code provides numerical results for arbitrary tensor and scalar integrals for scattering processes in general quantum field theories. For tensor integrals either the coefficients in a covariant decomposition or the tensor components themselves are provided. Collier  supports complex masses, which are needed in calculations involving unstable particles. Ultraviolet and infrared singularities are treated in dimensional regularization. For soft and collinear singularities mass regularization is available as an alternative. Program summary Program title: Collier Program Files doi: http://dx.doi.org/10.17632/dmdn2ph3x2.1 Licensing provisions: GNU GPL version 3 Programming language: Fortran95 Nature of problem: Evaluation of general one-loop multi-leg scalar and tensor integrals occurring in the calculation of one-loop corrections to scattering amplitudes in relativistic quantum field theories. Solution method: Scalar integrals are evaluated using explicit analytical expressions. Tensor integrals are numerically reduced to scalar integrals via different methods. Depending on the specific kinematical variables, an appropriate method is automatically chosen to optimize the resulting numerical accuracy. Restrictions: real momenta