Previous page	Up to the index	Next page

What if the entire MVD is not aligned with the beam? This can happen if the central magnet carriage is moved and does not return to an aligned position. From inspecting the carriage and its rollers and bearings, we estimate that at each end (north-south), there is less than 1/4 mm play. The rollers are spaced apart by about 4m. In this run, I rotated the MVD in the horizontal plane by 4 times the expected maximum, or 0.0286 degrees.

For high MVD hit multiplicity, the 'pseudo-tracking' agorithm is used (left column), and for low multiplicity, the 'correlation method' (right column). Horizontally, the input x,y,z of the event vertex is plotted, and vertically the reconstructed x,y,z is plotted. Not that in this run, the spread in x and y thrown was set to 0. If the method were perfect, all points would lie on the dashed diagonals. (postscript)

In the left column are the projections of the above 6 plots along the direction of the diagonals, giving the resolutions in x,y and z. (postscript)