Treatment of multiple scattering with the generalized Riemann sphere track fit

In this paper, we present a generalization of the Riemann sphere track fitting method. This generalization makes it possible to efficiently include multiple scattering effects in the estimation procedure. We also show that the Riemann fit can be formulated in an alternative way through a mapping to a paraboloid. This yields results equivalent to the standard formulation, but with the added advantage that measurements with errors both in RPhi as well as in the radial direction can be handled in a straightforward manner.