Tracking Software Task List
Software Flow Chart
In order to determine the electron momentum, a phase space will be calculated by using simulations to swim electrons through the field in each octant. The phase space will then serve as a momentum lookup table. The phase space coordinates are the vertex position in z, scattered angle phi, scattered angle theta, and momentum. The simulation will calculate the deflected angles phi and theta. Roughly 100 million points will be required for each octant. In addition to a lookup table, a direct momentum calculation will be available using standard Runge-Kutta methods to swim the particle through the field, and Newton's method to vary the momentum until the front and back tracks line up. The direct method will be used in the cases when the track lies outside the phase space and if the phase space resolution is inadequate, it will refine the initial guess from the lookup table. The situation may require a balancing between phase space resolution, which affects disk space and hard drive access speeds, and momentum variation, which affects CPU cycles and is affected by computer numerical errors.
QTR input format needs to be revised to match the DAQ-hits program outputs. At some level, an event structure will be needed. I envision that the output of QTR will be in ROOT, and so it may be useful to create an event 'skeleton' which contains all the QTR input and is then filled by QTR with track information.
2/13/8 : Region 1 & 2 - Progress is being made. Because there are only 2 planes for each wire direction, and due to the poor symmetry of triangular hit patterns, no pattern recognition will be used. A u,v, or x track segment is created for every hit position combination. A hit in the front and back plane results in up to 4 track segments. u,v, and x directions are then combined to reject all unphysical combinations. There are cases where ambiguities may still exist, requiring information from Region 1 for ghost track rejection. However, tracking will reconstruct all possible tracks through the HDC. HDC lab positions are required for tracking routines. A program that converts DAQ output into QTR input is also needed.
Author : Burnham Stokes
bestokes@jlab.org