Preparation of the TPC Track Information

TPC track information plays the significant role in the reconstruction with particle-flow technique. Hence program uses the parameters of charged track at the calorimeter face that taken from TPC reconstruction procedure.

Subroutine TPC_RECONST_PREP
calculates distances between charged track impact points at the calorimeter face and track helix hypothesis parameters; makes groups of tracks at the calorimeter face.

Input for this program is the arrays of $x(i), \; y(i), \; z(i)$ - coordinates of input point at the calorimeter inner surface, $P_x(i), \;P_y(i), \;P_z(i)$ - particle momentum at this point and $Q(i)$ - particle charge.

Now program used COMMON / CALOINPUT / that consists of an ideal TPC information.

Detailed actions:

$\bullet$ Subroutine initializes COMMONS.

$\bullet$ Sorts TPC tracks in decreasing order of their momentum.

$\bullet$ Calculates distance matrix for every two tracks at the calorimeter face. The simplest 3-d distance between two points at the calorimeter face is used now.

$\bullet$ Sorts distances between TPC charged tracks in increasing order and creates pairs of the nearest TPC tracks.

$\bullet$ Creates groups of the nearest tracks at the calorimeter face. The set of tracks is defined as a group if the distances between any pairs in group less then limit (see TPC_trk_Dist_Merge). The group configuration topologically described as graf by number of pairs and number of links between close tracks. Several group topologies exists: compact group - number of links more then number of pairs in group, extended group - number of links less then number of pairs in group, compact group with a tail and so on.

$\bullet$ Calculates coordinates and momentum for group of tracks.

$\bullet$ Creates the list of charged tracks that belong to some group.

$\bullet$ Creates the list of charged tracks that do not belong to any group in decreasing momentum order.

$\bullet$ Calculates parameters of predicted helix of charged particles in the calorimeter volume.

All calculated values are in /TPCTRACK/ and /CALOINPUT/ COMMONs.