Distance to the beam position:

Available for charged reconstructed tracks.

QDB (I)

distance of closest approach to beam axis

QDBS2 (I)

error² on QDB

QZB (I)

z coordinate of track point where QDB is measured

QZBS2 (I)

error² on QZB

QBC2 (I)

$\chi^{2}_{}$ due to QDB and QZB.

The coordinates of the beam position used to compute these values are QVTXBP(I) (see 6.4 on p.  ).

For more geometrical track attributes, see sections 8.2.1 and 9.1.