Track vertexing for trigger applications

In this paper, we present a novel vertexing algorithm for determining the point of primary interaction, based on the linear extrapolation of tracks in the vicinity of the beamline. The algorithm considers tracks as infinitely elongated ellipsoids, thereby reducing the track vertexing problem to a vertex-to-points proximity problem. We have implemented the concept in C++ with the aid of our previously reported NXV4 package three for vectors and matrices, which gives very good CPU performance.