ALIGNMENT: CURRENT SITUATION

The current vertex-finding algorith uses pseudo-tracking. All hits are connected, and projected to the z-axis. 'Good' combinations tend to pile up at the location of the true vertex. The method finds a maximum in the distribution of these projections.

The method currently assumes that the true vertex is exactly on the z-axis.The vertex may in fact be off-axis. There are three relevant numbers here:

1. the spill-to-spill position of the beam (sigma=xx mm).
2. the beam gets fatter from the start to the end of the spill (sigma=xx)
3. The systematic error on the absolute position of the MVD

Chips are mounted on C-cages 6 at a time, and not in pairs; We now have to define criteria in terms of placements of the chips on the cages, and then of placement of the cages relative to the MVD detector frame.