Simulation of light guidance in scintillating fibres for the LHCb upgrade

During the current long shutdown of the LHC the LHCb detector will undergo a comprehensive upgrade. An important part of this upgrade is the replacement of the current downstream tracking stations by a detector made of scintillating fibres. These fibres are wound and glued to form mats with a length of 2.5 m. Charged particles crossing the scintillator emit light which is then guided by total internal reflection towards silicon photo multipliers at the end of the mat. The amount of light observed at the end of the fibre is an important predictor for the performance of the system. This so called light yield is among other things affected by irradiation damage of the fibres. Hence it is important to understand and quantify these effects in order to predict the performance of the tracker during its life time. In this talk several approaches to the simulation of scintillating fibres are presented. Special emphasis is put on the development of effective models from simulation studies and measurements of single fibres.