In the L1 trigger after 2D vertexes have been found and for all
tracks in HLT and offline the phi information will be added to the
tracks.
The phi sensors are laid out as below in PR04_phi.ps.
There are 683 strip in the inner region and 1365 in
the outer region.
The strips are skewed from true phi to allow a slight stereo
angle. The stations are also fitted alternating with R upstream or
downstream which reverses the stereo angle in alternating
stations. Which means until the radius of a hit can be estimated
phi is not known.
Tracks from near the beam axis are expected to have roughly
equal phi values.
- Tracks are sorted by length with the longest tracks taken first
- For each 2D track the radius at last two stations with R clusters is calculated
- The actual phi of the "phi" clusters is estimated using the projected radius.
- Pairs of phi hits are compared and those with close enough in phi are added to the track and a 3D trajectory constructed.
- The track is projected backward and forward and phi hits, corrected for R of the extrapolation, are added if close enough
Tracks are then stored to be converted to tracks used in fitting later.
--
DavidHutchcroft - 09 Aug 2005