# Presentation: 099868

## Status & Update of track reconstruction in the Near Detector

- N. Saoulidou, Fermilab 10-3-04

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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

## 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

## 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

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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%)**

- Initial

- Final

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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...

- Initial

- Final

- N. Saoulidou (niki@fnal.gov). Fermilab

## Track Reconstruction  Purity (All Muon tracks no cut in completeness) 

-  The muon track purity remains basically **unchanged @ 95-96 %**

- Initial

- Final

- N. Saoulidou (niki@fnal.gov). Fermilab

## Track reconstruction characteristics  in the ND (Muons)  

**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 **

**U**

**V**

**Z (plane #)**

**Completeness **

- N. Saoulidou (niki@fnal.gov). Fermilab

## Track reconstruction characteristics  in the ND (Muons)  cont’d  

**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**

**U**

**V**

**Z (plane #)**

**Purity **

- N. Saoulidou (niki@fnal.gov). Fermilab

## 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

## 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

## 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