Sammendrag
The Gaussian Sum Filter is a track reconstruction algorithm for treating energy loss
by bremsstrahlung, and produces non-Gaussian estimates for the track parameters. This thesis explores a method of propagating these non-Gaussian errors into a non-Gaussian estimate of the invariant mass. It is tested if the method can be used to
improve the invariant mass resolution in ATLAS, and if it gives a good description of the errors on the invariant mass. The result showed that the invariant mass resolution is not improved, but a large improvement in the description of errors is found.