Primary Vertex Finding in Multivertex Events

In the CBM experiment [1] the Kalman filter based algorithm of primary vertex reconstruction is implemented [2]. The algorithm is developed for the case of single primary vertex events: all found tracks are used for the primary vertex reconstruction. The multivertex events availability is assumed by the physics program of the CBM experiment. In case of the multivertex event the situation is more complicated: the number of interaction points is unknown and there is no information about the belonging of the certain track to the certain vertex. Another problem is related to events with low track multiplicity. In this case the currently implemented algorithm will be very sensitive to each measurement, where measurements are tracks included to the primary tracks clusters. If the tracks, which are created by the secondary particles, are included into this primary tracks clusters the errors of the reconstructed primary vertex position could be increased dramatically and the position could be determined incorrect. Therefore the goal of this investigation is to develop the algorithm, which should determine the number of primary vertices and find the clusters of primary tracks, which form each vertex. The developed cluster finder algorithm is based on two assumptions: there is only one target and all primary vertices are positioned on the target. The algorithm consists of the following steps: