1. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20011 Topics for the TKR Software Review Tracy Usher, Leon Rochester Topics for the TKR Software Review Tracy Usher, Leon Rochester Progress in reconstruction Reconstruction – short-term plans Simulation Calibration issues Balloon-specific support Personnel and Schedule

2. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20012 Tracker Recon Where were we at the last workshop? Status at last workshop –Pattern recognition & track fit linked together within the context of the Kalman Filter. –Tracker reconstruction incorporated within the Centella framework –Tracker reconstruction used in the analysis of the Test Beam data and Monte Carlo.  Thanks Jose! Plan at that time –Separate the track fit from the pattern recognition. –Create: Track Extrapolator Pattern Recognition Track Fit (Kalman Fit)  Standard HEP Solution Personnel changes –Jose departs –Tracy and Leon arrive  Tracker Recon “in the shop”

3. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20013 Tracker Recon What is the goal of the reconstruction? To reconstruct the the direction and energy of gamma ray conversions in the tracker. –Must find and reconstruct the trajectories of the e + e - pair –Must determine the energy of the e + and the e - (individually) –Must find the common point of origin of the e + e - pair –From this information, determine the energy and trajectory of the incident gamma ray Find and reject background

4. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20014 Tracker Recon New kids have a few misconceptions… –How hard can it be? –What happened to the magnetic field? –This lead stuff is not helping the tracking! –What happened to the stereo layers? –Isn’t the Monte Carlo supposed to also give you the answer? –Electrons don’t get along well with others –Learning c++ will be easy!  Ok, this is not your standard tracking problem…  Where/how do we get started?

5. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20015 Tracker Recon Reality according to Tbsim…

6. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20016 Tracker Recon How do the new kids proceed? Need to: –Learn (enough) c++ to be able to understand and modify the code – ultimately write new code –Learn the GLAST “system” –Learn how the existing code works –Get the full appreciation for the problem –Make progress along the path set forth at the last workshop Approach: –Take on the task of separating the pattern recognition from the track fit –Work within the Test Beam / Centella framework –Implement a new pattern recognition (“link and tree”) which is independent of the Kalman Filter –Attempt to perform a simple pointing resolution study comparing fit tracks to the first links

7. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20017 Tracker Recon Pattern Recognition – Kalman Filter approach Kalman Filter –Particle trajectories are straight lines –Changes in trajectory due to multiple scattering are gaussian in nature –Pat Rec looks for gammas (vee’s), then for particles But… –Multiple scattering is not entirely a gaussian process –Bremsstrahlung results in many low(er) energy e + and e - tracks along principal path Leading to large scattering angles for principle e + or e - And confusing the pattern recon

8. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20018 Tracker Recon Pattern Recognition – simple approach Implement a “Link and Tree” algorithm –Simplest algorithm to dive into the code –Allows one to follow pre-shower development –“Longest, Straightest” branch is trajectory of the primary e + or e - Can be projected to calorimeter for initial clustering Passed to Kalman Filter for track fit –Other branches can (hopefully) give more information on energy of primary e + or e - pair –As with Kalman Filter, Pattern Recognition runs in 2-D Association to 3-D done after initial 2-D tracking finding –Strategy is to find individual tracks first Then put tracks together to form/find gamma conversions

9. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 20019 Tracker Recon Pattern Recognition – simple approach Algorithm –Links formed between all pairs of clusters in adjacent layers –Beginning with the top most layer containing cluster hits, links are combined to form a tree structure –Links are not allowed to be shared –Clusters are allowed to be shared –Trees sorted by longest and straightest for association to 3-D

10. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200110 Tracker Recon Pattern Recognition – simple approach

11. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200111 Tracker Recon Pattern Recognition – simple approach Current Status –“Link and Tree” algorithm in 2-D operational –Rudimentary association of 2D tracks to 3D operational Tracks start in same layer Tracks have same length Straightest tracks associated –Longest, straightest tracks are fit by Kalman Filter –Only looking at single charged particles at this point Not quite ready for gammas

12. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200112 Tracker Recon Some initial results Look at TBsim e + runs –Positrons incident normal to the first tracker layer –Energies: 0.1, 0.25, 0.5, 1.0, 2.0, 5.0, 10.0, 20.0 GeV 3-D Track Reconstruction of e + requirements: –Track must be 12 or more layers in length –Must start in first tracker layer Look at: –Track recon parameters Number reconstructed and passing above cuts Length of tracks Etc. –Pointing at start of track comparing Compare between fit parameters at first hit and first link

13. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200113 Tracker Recon Some initial results Track Accounting  = 951/1000 = 95.1% Number tracks/event = 1.6 Length of tracks = 11.1

14. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200114 Tracker Recon Some initial results

15. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200115 Tracker Recon Some initial results 3-D Pointing Resolution Take mean value 2-D Pointing Resolution X Fit Gaussian 2-D Pointing Resolution Y Fit Gaussian

16. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200116 Tracker Recon Some initial results  Resolution in 3-D pointing for Kalman Fit and for first link is approximately the same…

17. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200117 Tracker Recon Some initial conclusions “Link and Tree” Pattern Recognition –Simple algorithm implemented within the Centella context –Shows promise for: Finding primary e + and e - tracks Keeping track of pre-shower development – aid in helping to keep track of energy loss of the primary tracks Providing initial pointing into the calorimeter –Don’t need to know the energy before getting the track –Track finding – calorimeter – track fit – calorimetry – track fit - … –More careful studies needed before really saying anything about pointing resolution… –Needs refinement (= rewrite) if really want to proceed… New kids are getting to be conversant in c++ New kids have learned a (small) part of the GLAST system New kids have a much greater “appreciation” of the problem

18. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200118 Tracker Recon Short term plans Balloon flight needs tracking soon! –Tested tracking exists within the centella framework –Move the existing code The first goal is to move the existing TB_recon into the Gaudi framework Allows us to stop working on legacy code. –Connect to New Geometry This will allow us to develop code which can be used for all GLAST configurations. –Write new data converters for Test beam data and MC Glastsim output Cosmic data / Balloon flight Continue looking at Pattern Recognition alternatives

19. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200119 Calibration Issues There are three parts to each problem below: the calibration algorithm, the database, and the automated production process Bad Strips –Hot/dead strips –Common mode failures: Chips, ladders, towers Alignment –Current status –What’s ultimately needed TOT (Time-over-Threshold) –Calibration signal?

20. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200120 Bad Strips Currently, the bad strips are recorded in an ASCII file, by layer and strip number. These are used by the reconstruction to kill bad strips and to join clusters separated only by bad strips. For the full detector: – The production database will record bad strips at different levels: for example, chips, detectors, ladders, layers, and (shudder!) towers. – Since the state of the strips will need to be monitored regularly, we particularly need a reliable automatic system to detect bad elements and update the database.

21. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200121 TKR Alignment An alignment was done on the BTEM using test beam data, first with entire layers, and then with individual ladders.

22. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200122 Finding Residuals Fitting planes Method: Find the a track. Fix a line through the clusters in planes 8 & 15. Calculate the residuals with respect to that line. Residual

23. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200123 Layers and Ladders The original residuals were as big as 200 μm. (σ  40 μm) Layers were shifted to minimize the residuals. Two layers can be fixed (or the overall change of position and slope can be set to zero) because there are two degrees of freedom in the original problem The resulting residual distribution has σ  25 μm.

24. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200124 Layers and Ladders (2) To improve resolution, the positions of individual ladders were adjusted with respect to ladders above and below, using normally-incident tracks, with the final σ  15 μm.

25. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200125 Alignment: the New Frontier A complication: In the full detector, many tracks will cross ladders and towers. Slanted tracks allow the alignment of adjacent ladders and towers. This is more complicated because now all the elements are tied together with springs, and there are six parameters per object: x, y, z, and 3 rotations. Solving this problem usually leads to big matrices!

26. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200126 Time-over-Threshold (TOT) For each layer, the TOT is measured by combining all the fast-OR’s for each event. The TOT measures the width of the pulse at some fixed pulse height, and is thus roughly proportional to the largest charge deposited on any strip in the layer. t1t1 t2t2 Distribution of TOT values for a 20 GeV positron run (normal incidence) with a Landau fit overlaid. (Test beam data)

27. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200127 TOT (2) In the test beam, the TOT was sensitive to the photon conversion point. But this was at normal incidence. Will this still work for angled tracks? We have test beam data to answer this question! (I think…) How do we calibrate the TOT? What is the correct level? γ e+e+ e-e-

28. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200128 Plans for Simulation Glastsim/GEANT4 outputs MC truth Digis produced from MC hits –Digis and hits can be read by Recon Upgrades to Generation –Realistic Geometry –Fluctuations (for TOT) Upgrades to Digitization –Charge sharing –Dead strips/chips/SSDs –Overlay of background Model Real data –TOT Common Geometry

29. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200129 Charge Sharing, Fluctuations and all that Calculated TOT response is sensitive to details of the generation and digitization. Low Medium High

30. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200130 Balloon-specific Support Certain aspects of the balloon-flight data may require special support. Special reconstruction algorithms –Dealing with high backgrounds –Picking out photons in hadronic showers Analysis –Projecting to active targets –Finding interaction vertex Calibration –Dead/hot strip list –Probably no alignment required to reconstruct tracks, but we may want to demonstrate that we can do it. A use for the expected 10 7 protons? –Same for TOT

31. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200131 A Preliminary Personnel/Task Inventory Institutions Pisa Santa Cruz Santiago de Compostela SLAC People 2 3 1 (through mid-Feb) 2 Tasks Port of Recon to Gaudi Development of Recon Simulation Calibration

32. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200132 A Preliminary Personnel/Task Inventory Institutions Pisa Santa Cruz Santiago de Compostela SLAC People 2 3 1 (through Mid-Feb) 2 Tasks Port of Recon to Gaudi Development of Recon Simulation Calibration And tentative set of matches...

33. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200133 TKR Software Schedule Near-term (Feb—Mar) Port recon to Gaudi Read TB data/MC -- verify port Refine recon algorithms Implement digitization Read/recon cosmic data Specify calibration databases Medium-term (Apr—May) Refine digitization Read/recon Glastsim/GEANT4 digis Implement calibration databases Implement single-tower alignment algorithm Test alignment code with cosmics Implement hot/dead strip calibration Write special code for balloon flight Refine TKR-specific GEANT4 code Long-term (June— ) Refine balloon recon Perform balloon analysis Connect new geometry Implement full detector geometry Develop multi-tower alignment algorithm Demonstrate full detector capability –gamma detection and measurement –background rejection –optimized PSF –automated calibration

34. GLAST LAT Offline SoftwareWorkshop - SLAC, Jan. 16-19, 2001 TKR Software Review -- Jan. 17, 200134 That’s All Folks!