Global Reconstruction Checks

1. Global Reconstruction Checks Rajarshi Das November 17, 2010 Global Reconstruction Meeting Colorado State University

2. Overview • Motivation: Previous checks suggest several problems with Global Reconstruction • Misses P0D Tracks • Reconstructs multiple tracks for the same true track • Incorrectly applied Energy Loss in the P0D • Sample: Muon Particle Gun • 1000 events processed with v7r21, v8r5p3 and HEAD versions • 0 to 2 GeV flat Energy distribution • All vertices in P0D • Cuts (from Truth): • Only single Lepton track in Event • Vertex in P0D Fiducial region • Muon Track doesn’t stop in P0D

3. Broken Tracks: v8r5p3 • Procedure: • Find events from oaAnalysis files with multiple Global reconstructed tracks associated with the SAME muon (from TGlobalPID::TrueParticle) • Filter said events from oaRecon files • Hand scan using plot-event.exe • Problems: • Should be 1 solid red line • Multiple tracks reconstructed • P0D track clearly not stitched together with tracker tracks

4. Further Examples Bug? (Drift plane)

5. P0D  Global Failures • Look at the FIRST GlobalPID in each event that is associated with the true muon track (via TGlobalPID::TrueParticle) • Start position of most Global Tracks are @ TPC US face • VERY large discrepancy in true vertex position and global track start position • Indicates that GlobalPIDs in our selection do not include the P0D piece Distance from True vertex to track start Z position of Global Track start

6. Success/Failure Rates

7. Findings/Conjectures (HEAD) • Finding: Global PIDs exist that have P0D pieces! • I only look at Global PIDs with: • TGlobalPID::TrueParticle::PDG == 13 (muon) • Reconstructed momentum not equal to 0 or 10000 • Conjecture: Above two cuts drops the GlobalPIDs with P0D pieces (probably the PDG cut) • Global Reconstruction is not correctly stitching together tracks • Potentially oaAnalysis bug?

8. True Pm – Global Reco. Pm • From v7r21 to v8r5p3 to HEAD, we see an improvement in reconstructed momentum • Implies correct Energy Loss application? • Algorithm: Should take TPC measured momentum, project track to P0D vertex, correct for energy loss in P0D • But if Global Reconstruction is missing P0D tracks, how can it project to P0D Vertex? Mean 74MeV v7r21 Mean 266MeV v8r5p3 Mean -14MeV HEAD

9. Energy Loss Check (1) • Does Global Reconstruction correctly include energy loss in P0D? We can check! • Materials list for P0D gives average dE/dx of ~565 MeV for whole P0D • P0D length is ~2.5 m • Avg. Energy loss = 565 MeV / 2.5 m = 0.226 (MeV / mm) • Use p0drecon’s reconstructed track length in P0D, average energy loss in P0D and TPC measured momentum to calculate Momentum at P0D Vertex Track length of P0D piece from p0drecon True Pm minus Pm as measured by Tracker only Mean 187MeV

10. Energy Loss Check (2) True Pm minus Pm Corrected by hand @ .226 (Mev/mm) P0D Energy Loss Superimposition of “By Hand” result and Global Reconstruction result • Beautiful agreement with results from current Global Reconstruction algorithm • Looks like Global Reconstruction is definitely doing this part correctly “By Hand” Mean 14MeV Global Reco.

11. Conclusions • Global Reconstruction is not stitching together all the tracks properly • About 36% of nice muon tracks are getting reconstructed as multiple tracks in Tracker • Almost 90% of events are getting multiple tracks reconstructed • P0D pieces are not getting stitched into GlobalPIDs • GlobalPIDs that pick up P0D pieces are likely not correctly associated with corresponding True Track • Momentum reconstruction significantly improved in newer versions • Quick comparison shows Global Reconstruction is applying P0D energy loss correctly (but how??) • Future Work: • Isolate oaRecon from oaAnalysis issues/bugs • Look into the True Track association issue