sPHENIX tracking discussion

["Pereira Da Costa, Hugo Denis Antonio" <hugo.pereira-da-costa AT lanl.gov>]

Hi all, in particular Tony, Joe

I might have found the reason why I got poor upsilon reconstruction 
efficiency and good single track reconstruction efficiency when including 
distortions and correction.

I think the issue comes from the TPC to silicon matching, that does not 
properly include the distortion corrections.

The code PHSiliconTpcTrackMatching line  343 

uses _tracklet_tpc->get_phi(_cluster_map,_tGeometry); to calculate a given 
TPC seed phi, and match to silicon phi. This version of get_phi accesses the 
cluster map directly and does not account for distortion corrections. So the 
matching is poor.

Tony: does that sound like a plausible explanation ? Did you compare the 
number of MVTX hits in tracks with and without distortion+reconstruction ?

The fix is "easy" I think: the TpcTrackMatching code must first loop over the 
clusters, calculate global positions while including the distortion 
corrections (as done elsewhere) and pass that to the get_phi method, rather 
than relying on the internal implementation.

Does that make sense ? If yes, I can implement.
I would also check if there are other occurrences of this elsewhere in the 
code.


Hugo