The MVD barrel showing only the silicon panels, arranged in 6 sectors and 2 concentric barrels. Strips are perpendicular to Z. Note the missing panels in the central top and side regions.

First, the Z-vertex is found by drawing lines, sector by sector, through each of the outer barrel hits and each of the inner barrel hits, and projecting these 'tracks' onto the z-axis. The Z-vertex is found by locating the maximum in the distribution of these projections. The arrow indicates the true vertex position at 5.56 cm. The pseudo-tracking method found the vertex at 5.55 cm.