Vertex reconstruction for proton-proton collisions in ALICE

Reconstructing the interaction vertex is a challenging task in the low multiplicity environment of pp collisions at the LHC. The two innermost layers of the Inner Tracking System (ITS), made of pixels, allow to obtain a first estimate of the vertex position, which can be provided also in a quasi-online mode, since only the local reconstruction is used. The optimal vertex measurement is obtained after the full event processing, using the tracks reconstructed in the ALICE barrel detectors. We present the methods for primary vertex reconstruction in pp collisions using pixels and tracks reconstructed in the ITS+TPC or in the TPC only. We also show the performance of the vertex finder in reconstructing displaced vertices originated by short-lived particles like charmed mesons.