1. N. Saoulidou (niki@fnal.gov). Fermilab 1 Status & Update of track reconstruction in the Near Detector N. Saoulidou, Fermilab 10-3-04

2. N. Saoulidou (niki@fnal.gov). Fermilab 2 Outline Summary of Corrections & Modifications done so far (after the previous Collaboration Meeting). Improvement (Initial & Final Results) on - Track reconstruction efficiency - Track Completeness (and Effect of Slicing) - Track Purity Summary – On going work

3. N. Saoulidou (niki@fnal.gov). Fermilab 3 Modifications & Corrections on ND tracking Code tuning, related with how the code handles events occurring in the partially covered plane area (which is identical to the spectrometer region (1/5 planes instrumented) except from the Plex. Modification on the way “duplicate” 3D tracks are examined : –Initially the percentage of identical hits was examined for all track strips (U and V together). –There were some cases were false 3D solutions existed having the correct 2D Line in one view and the wrong 2D Line in the other view. –The code is now modified to examine percentage of identical strips in each view and keep the solution with the largest number of planes. Corrections on the plane number from which the Plex starts from > 121 to >=121! –Due to that error a few quite clear tracks were missed because the code was unable to reconstruct the correct 2D line in the U view.

4. N. Saoulidou (niki@fnal.gov). Fermilab 4 Track Reconstruction Completeness (All tracks with completeness > 0) The previous changes resulted in an increase on the number of reconstructed tracks (796->899) and an increase in track completeness ( 85%->88%) Initial Final

5. N. Saoulidou (niki@fnal.gov). Fermilab 5 Track Reconstruction Completeness after slicing (All tracks with completeness > 0) This actually reflects the track reconstruction quality since it is performed after the Event Slicing. There is also increase on the number of reconstructed tracks (796->899) and an increase in track completeness ( 86%->89%) Initial Final

6. N. Saoulidou (niki@fnal.gov). Fermilab 6 Track Reconstruction Purity (All tracks with completeness > 0) The increase on the number of reconstructed tracks (796->899) did not decreased (or increased) track purity ( 92%->92%) Initial Final

7. N. Saoulidou (niki@fnal.gov). Fermilab 7 Track Reconstruction Completeness (All Muon tracks no cut in completeness) The previous changes resulted in an increase on the number of reconstructed muon tracks (697->801) and an increase in track completeness ( 87%->89%) InitialFinal

8. N. Saoulidou (niki@fnal.gov). Fermilab 8 Track Reconstruction Completeness after Slicing (All Muon tracks no cut in completeness) There is also an increase in muon track completeness after slicing ( 88%->90%) as expected… InitialFinal

9. N. Saoulidou (niki@fnal.gov). Fermilab 9 Track Reconstruction Purity (All Muon tracks no cut in completeness) The muon track purity remains basically unchanged @ 95-96 % InitialFinal

10. N. Saoulidou (niki@fnal.gov). Fermilab 10 Track reconstruction characteristics in the ND (Muons) These plots show that : -There is a clear preference in the number of reconstructed muon tracks towards the fully instrumented ND region, which is not so pronounce (or not pronounce at all) for the z position of the neutrino vertex with respect to the Plexed region. - But the track completeness is ~ the same for all U V Z positions Completeness UV Z (plane #) Completeness

11. N. Saoulidou (niki@fnal.gov). Fermilab 11 Track reconstruction characteristics in the ND (Muons) cont’d These plots show that : -There is a clear preference in the number of reconstructed muon tracks towards the fully instrumented ND region, which is not so pronounce (or not pronounce at all) for the z position of the neutrino vertex with respect to the Plexed region. - But the track purity is ~ the same for all U V Z positions Purity UV Z (plane #) Purity

12. N. Saoulidou (niki@fnal.gov). Fermilab 12 Track reconstruction characteristics in the ND (Muon Momentum ) True Muon Momentum (reconstructed muons: black, all muons : red) Difference % between true and reconstructed muon momentum Most of the muon tracks that are not reconstructed are with momentum below 1 GeV (these are in principle more sensitive to ND geometry “peculiarities”) The resolution of the muon track momentum reconstruction is ~ 10% (for the majority of the tracks) with a clear asymmetry at negative values (mean @ ~ -4%)

13. N. Saoulidou (niki@fnal.gov). Fermilab 13 Muon track reconstruction efficiencies Muon track reconstruction efficiency is 86 % for : –z < plane 115 (5 planes upstream the plexed region) –Number of true muon planes > 5 (in order to be able to reconstruct 2D lines in each view) –No Cuts in U and V neutrino vertex position Muon track reconstruction efficiency is 92 % for : –z < plane 115 (5 planes upstream the plexed region) –Number of true muon planes > 5 (in order to be able to reconstruct 2D lines in each view) –U neutrino vertex > 0 and V neutrino vertex < 0 (fully instrumented region)

14. N. Saoulidou (niki@fnal.gov). Fermilab 14 Summary & On going work Making corrections and additions to the ND tracking code the track reconstruction efficiency and all track characteristics (completeness & purity) have been improved. The 92 % of track reconstruction efficiency in the fully instrumented region of the ND, the 90% of track completeness and 95 % of track purity are quite satisfactory and I think the ND tracking code is in quite good shape. From now on I will focus more in ND track fitting trying to improve mostly timing issues.