1. Reconstruction Overview and Status (representing a lot of people)
Data Challenge II
Reconstruction Overview and Status
-or- Don’t Panic
Tracy Usher
(representing a lot of people)

2. Outline Introduction Picture of where we are going
Overview and status of TkrRecon
Overview and status of CalRecon
Picture of what will be implemented for DC-2
Summary

3. Introduction Defintion of Reconstruction
What do we mean by “Reconstruction”?
Reconstruction begins after the digitized information has been converted to a particular systems “processed” data:
TkrClusters in the Tracker
CalXtalRecData objects in the Cal
Allows for calibrations to be applied (particularly in the Cal) before getting into the business of reconstructing the event
Reconstruction ends (ideally) when the event has been categorized and the energy and incoming direction have been determined with no further corrections necessary
Just before writing to the PDS or production of ntuple
Note: currently some of the above is done in the merit/AnalysisNtuple stage
Hope to change this before done

4. Introduction General Strategy
Gaudi Algorithms
Algorithms define the reconstruction tasks and control the sequence in which they are performed
Gaudi Services
Provide “global” information across events (e.g. geometry)
Gaudi Tools
Implementation of specific reconstruction tasks
Interact with Algorithms through abstract interfaces to allow for straight forward interchangeability
Gaudi Transient Data Store (TDS)
Globally accessible repository containing the results of each reconstruction task
Provides communication between the stages of reconstruction

5. Flow of Reconstruction Gaudi Algorithm Sructure: The End Goal
Digitization
PDS/ntuple Output
CalRecon Pass I
TkrRecon Pass I
CalRecon Pass II
TkrRecon Pass II
AcdRecon
Event Summary
CalXtalRecAlg
TkrClusterAlg
TkrTrackFitAlg
EventSummaryAlg
CalClusterAlg
TkrFilterAlg
TkrVertexAlg
AcdReconAlg
TkrFindAlg
CalEventEnergyAlg
CalMipFinderAlg
Key
Existing Algorithms
New Algorithms
Not “Recon”
TkrTrackFitAlg
CalEventEnergyAlg
TkrVertexAlg

6. TkrRecon Overview and Status
Major modifications to TkrRecon:
Restructuring/Streamlining of TDS output
Refactor much of the TkrRecon code
From pat rec through vertexing – pretty much all of it
Introduce new features
Filter step, test/alternative pat rec, etc.
Infrastructure
Hot/dead channels
Alignment
Etc.
Most tasks completed by around early Spring
Many rounds of bug fixes complete
Hot/dead channels, alignment starting to be tested
I&T folks have adopted latest TkrRecon
Beating it/us up on a regular basis

7. TkrRecon TDS output Streamline the main TDS output: TkrClusters
TkrTrack
Now output of Track finding, modified by Track Fit
Contains global track parameters and a list of Hits for each silicon plane (existing or not) crossed from the first to last “real” hit of the track
TkrTrackHit
In turn contains TkrTrackParams containing the track fit parameters at each hit on the track
Also contains a track status word giving details of status of the track finding/fitting, describing parameters used, etc.
TkrVertex
Major changes include
addition of TkrTrackParams to provide a uniform method of extract track parameters
Vertex status word similar to that for tracks

8. TkrRecon Various Improvements
Track Finding:
Define common tool interface for Pattern Recognition code
Combo Pat Rec extensively refactored
Combinatoric search logic localized to ComboFindTrackTool
Utilizes a new FindTrackHitsTool
Utilized a Kalman Filter track following approach to associate hits to tracks
Track Fitting:
New implementation of Kalman Filter which provides control, via job options parameters, of:
Particle mass hypothesis (e.g. can fit muons “easily”)
Energy loss mechanism (radiation loss, Bethe-Bloch, etc.)
Hit error determination (e.g. slope corrected)
Various test options (e.g. turning off Multiple Scattering errors)
Adds new features:
“Smoother Memory” option – point at which subsequent hits on tracks no longer contribute to pointing
Hit Residuals fits – drops hits from fit to get “unbiased” residuals
“Recursive Fit” to fit for track energy
Etc.

9. TkrRecon Various Improvements (continued)
Vertexing:
Employ new/updated track combination strategy to improve quality of two track vertices
Output TkrTrackParams for consistency of use
Tracker Energy estimate via Multiple Scattering
Rewrite of “computeMSEnergy” for determining energy in Tracke from tracking alone (relying on multiple scattering)
Improvements to resolution, especially below ~200 MeV
Track Energy Assignment
New TkrTrackEnergyTool for apportioning total event energy to “best” two tracks in event
Implement Alignment shifts into reconstruction
In progress

10. TkrRecon Some New Stuff
Tracker Filter Step
Goal: Do not attempt to run pat rec on “obvious” garbage events
Method: a fast “event shape” analysis to determine if hits in tracker appear to be “track-like” or “cloud-like”
Status: Testing a moments-analysis based method
Monte Carlo Pattern Recognition
Goals:
Perform end-to-end testing of track fitting and vertexing to determine limits to tracking provided the “right” hits.
Pattern Recognition Efficiency studies
Method: Combine MC output (McParticles and McPositionHits) and relate to TkrClusters to from MC tracks which can be fit and vertexed
Status: Working and used in some muon hit error studies
“Global” Pattern Recognition algorithm
Goal: Provide another method to study various Pattern Recognition issues and understand possible solutions
A Method: Use 3d space points (TkrPoints), linking possible combinations of hits to form track possibilities. Tracks formed from best unique combinations of allowed possibilities.
Status: Preliminary version available for testing
Is it needed?

11. CalRecon Overview and Status
The Calorimeter is an information rich detector
Hodoscope: Think of as a low resolution strip detector
But with “pulse height” and longitudinal position information
Attempt to maximize use of this information
Break reconstruction into logical pieces
Provide interfaces to each step to allow easy introduction of new techniques
e.g. clustering
Provide new tools to aid in background rejection
e.g. MIP finding
Redefine TDS classes to easily include extra information
A work very much in progress at this point
First results of bailing wire and chewing gum version in Bill’s talk

12. CalRecon New Reconstruction Structure
Cal Clustering: CalClustersAlg
Associate hit crystals which are “connected”
Current method is to associate all hit crystals into a single cluster
Exploring alternate methods
Really aimed at enhancing background rejection or improving cluster centroid/axis determination
Cluster Finding Tool interface and TDS output defined, new tools can be switched in easily
Create TDS output: CalCluster
Total energy = sum of energies of crystals
Cluster centroid and axis
Some “quality” parameters
A clustering status word
Type of clustering algorithm run
Status of various calculations (in case they fail)
Classification of cluster (e.g. “miplike”)
One new/resurrected feature:
Cal Centroid position and axis are determined from a “moments analysis” as was done circa 1998 (?)
Appears to be much better at including position and energy position from each crystal than the line fitting version used more recently
Work in progress to resurrect the full iterative moments analysis

13. CalRecon New Reconstruction Structure
MIP Finding: CalMipFinderAlg
Goal: Search for collections of hit crystals which are consistent with the traversal of a Minimum Ionizing Particle
Very powerful background rejection tool
Details of this will be presented in Fred’s talk
Code is very nearly running within the new Gaudi/CalRecon structure
Stay tuned for further progress reports

14. CalRecon New Reconstruction Structure
Energy Correction Step: CalEventEnergyAlg
Two steps to this algorithm:
Run the collection of energy correction tools that exist
Select the “best” energy correction for the particular event
Energy Correction Tools exist for both passes of CalRecon:
CalRecon First Pass:
CalRawEnergyTool
no correction, outputs raw cluster parameters for first pass tracking
CalRecon Second Pass:
Shower profile fitting
Leakage Corrections
“Geometry” corrections
Etc.

15. CalRecon New Reconstruction Structure
Energy Correction Step: CalEventEnergyAlg
Results of each correction tool returned in a “standard” CalCorToolResult TDS object:
An identifier for the particular correction tool
A set of CalParams (energy, centroid position/axis and errors)
A “chi-square”
A status word
A list of correction tool specific output which can be used in the final energy determination step
Final Energy Selection Step:
Ultimate idea: use a classification tree to select best energy based on all returned information
Current studies: Use results of CalValsTool
Final Ouput to TDS: CalEventEnergy
“Best” Calorimeter Parameters
The now ubiquitous status word
List of CalCorToolResult objects from all correction tools

16. Flow of Reconstruction Gaudi Algorithm Sructure: Envisioned for DC-2
Digitization
PDS/ntuple Output
CalRecon Pass I
TkrRecon Pass I
CalRecon Pass II
TkrRecon Pass II
AcdRecon
Event Summary
CalXtalRecAlg
TkrClusterAlg
TkrTrackFitAlg
EventSummaryAlg
CalClusterAlg
TkrFilterAlg
TkrVertexAlg
AcdReconAlg
TkrFindAlg
CalEventEnergyAlg
CalMipFinderAlg
Key
Existing Algorithms
New Algorithms
Not “Recon”
Not Fully Ready
TkrTrackFitAlg
CalEventEnergyAlg
TkrVertexAlg

17. Summary
Since DC-1 both TkrRecon and CalRecon have undergone extensive restructuring
Improvements in the code
Improvements in the output
Implementation of new tools to aid event selection and analysis
As a result, should see improvements in
Background rejection
PSF Tail suppression (I hope!)
Energy Resolution
(Hopefully) reconstruction efficiency
First version now running
See Bill’s talk this afternoon for current results

18. BasicOptions.txt
Reconstruction.Members={ "Sequencer/Cal1", "Sequencer/Tkr", "Sequencer/Cal2", "Sequencer/TkrIter", "Sequencer/Acd" };
// First pass of Cal Recon - full recon...
Cal1.Members = { "CalXtalRecAlg", "CalClustersAlg/first", "CalMipFinderAlg", "CalEventEnergyAlg/RawEnergy" };
// First pass of Tkr Recon
Tkr.Members = { "TkrReconAlg/FirstPass" };
// Second pass of Cal Recon - energy corrections only
Cal2.Members = { "CalEventEnergyAlg/second" };
// Second pass of Tkr Recon
TkrIter.Members = { "TkrReconAlg/Iteration" };