Status & Update of track reconstruction in the Near Detector

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

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

5. Track Reconstruction Completeness after slicing (All tracks with completeness > 0) Final Initial • 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%) N. Saoulidou (niki@fnal.gov). Fermilab

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

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

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

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

10. Track reconstruction characteristics in the ND (Muons) Completeness U V • 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 Z (plane #) N. Saoulidou (niki@fnal.gov). Fermilab

11. Track reconstruction characteristics in the ND (Muons) cont’d Purity U V • 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 Z (plane #) 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%) 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) 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. N. Saoulidou (niki@fnal.gov). Fermilab