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Raiders of the lost photons

Gamma-ray Large Area Space Telescope. Raiders of the lost photons. Elisabetta Bissaldi University & INFN Trieste, Italy SLAC, USA. Outline. Introduction Photon selection with MC algorithm Results from cosmic ray data for integrated 2, 4 and 6 towers configurations

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Raiders of the lost photons

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  1. Gamma-ray Large Area Space Telescope Raiders of the lost photons Elisabetta Bissaldi University & INFN Trieste, Italy SLAC, USA

  2. Outline • Introduction • Photon selection with MC algorithm • Results from cosmic ray data for integrated 2, 4 and 6 towers configurations • Study of vertex topologies • Summary

  3. Photons 2 tracks = VERTEX Muons NO VERTEX ? g Topologies for Dummies g m W W SI SI SI SI e+ e- In TkrRecon: 1 track ≡ VERTEX

  4. g Topologies in real life Often one of the 2 tracks is missing! No Si hits No Si hits (edge) Narrow separation Short track Compton angle scattering W W SI SI SI SI W W W SI SI SI SI SI SI

  5. Original idea... • Bill Atwood’s talk presented at the 3rd IA Workshop in march 2005 • Develop g finding algorithm: • Classification trees • Monte Carlo samples • AllGamma • Surface Muons • Cosmic ray data sample • Test RUN 140001338 for single tower  g candidates sample (5% of triggers)

  6. MC for 1 tower configuration Developed Initial selection cuts Defined 2 g topologies Developed algorithm classification trees Applied algorithm in data MC for 2, 4, 6 towers configurations Same Used only 1 g topology Searched for simple cuts using main variables Applied cuts in data Studied vertex topologies BB Challenge BILL BETTA More details in the next slides...

  7. Same Focus on first g topology VtxAngle > 0. “VERTEX” Same Initial conditions TkrNumTracks > 0 CalEnergySum > 10 MeV Definition of 2 g topologies 3. VtxAngle > 0. VtxAngle ≡ 0. “VERTEX” “1TRACK” Tkr1ToTFirst > 1 MIP Initial selections W W W SI SI SI SI SI SI

  8. Track projection Found track Calorimeter Electronics Additional variables • Tkr1SSDVeto > 1 • Use Tracker in self Veto Mode to replace ACD • At least one hit plane before start of track • same

  9. Bill’s Classification Trees Variables used to select g: • Tkr1ToTTrAve • Tkr1Chisq • Tkr1SSDVeto • Tkr1TotFirst • Tkr2Chisq • Tkr2FirstChisq • CalEnergySum VERTEX TOPOLOGY * * From Bill’s talk

  10. MC AllGamma 1 x 106 events 33341 trig. events Isotropic 18 MeV – 18 GeV v5r0608p7 MC Surface Muons 4 x 106 events 219322 trig. events Isotropic PDG formula and low energy extension v5r0608p7 Betta’s MC/DATA samples • DATA Cosmic Rays • 2 Towers: RUN 135002134 (462678 trig. events) • v5r0608p6 • 4 Towers: RUN 135002778 (61996 trig. events) • v4r060302p23 • 6 Towers: RUN 135004075 (390035 trig. events) • v5r0608p6

  11. Tkr1SSDVeto MC All Gamma MC Muons no cuts no cuts all cuts all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>1 Tkr1SSDVeto>2 ?

  12. Tkr1SSDVeto MC All Gamma MC Muons no cuts no cuts We lose 10% of photons and 70% of muons all cuts all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>2

  13. Tkr1SSDVeto MC All Gamma DATA no cuts no cuts We lose 10% of cosmic ray data all cuts all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>2

  14. Tkr1ToTTrAve MC All Gamma MC Muons no cuts no cuts all cuts all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>2 Tkr1ToTTrAve>1.3?

  15. Tkr1ToTTrAve MC All Gamma MC Muons no cuts no cuts We lose 5% of photons and 70% of muons all cuts all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>1 Tkr1ToTTrAve>1.3

  16. Tkr1ToTTrAve MC All Gamma DATA no cuts no cuts We lose 20% of cosmic ray data all cuts TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>1 Tkr1ToTTrAve>1.3 all cuts

  17. 2 Towers Results Similar results were obtained for 4 and 6 towers! (ask me later) TkrNumTracks>0 +CalEnergySum>10. +VtxAngle>0. +Tkr1TotFirst>1 +Tkr1SSDVeto>2 +Tkr1ToTTrAve>1.3 Cuts are cumulative!

  18. 2 Towers Results 100 % 10 % 1 % 0.1 % 0.01 % MC AllGamma 5 MC Muons 1 VtxAngle>0. DATA Tkr1SSDVeto>2 Tkr1ToTTrAve>1.3 0.01 STEPS 1 2 3 4 5 6 Cuts are cumulative!

  19. g dir W SI SI tracks g candidates with Event Display g dir hit tracks

  20. g dir W SI SI tracks g candidates with Event Display g dir tracks

  21. g dir W SI SI tracks g candidates with Event Display g dir Different Vertex Topologies tracks

  22. g dir g dir W W SI SI SI SI tracks tracks Topologies à la carte g dir W SI SI tracks  DOCA = Distance Of Closest Approach

  23. VtxStatus • Vertexing Variable in the Merit Ntuple • Summary of track composition and topology MC All Gamma 2 Towers no cuts ?

  24. VtxStatus bit pattern 21 + 25 + 27 = 162 1=true

  25. 0 1 162 128 162 34 128 16 43 % 28 % 12 % 7 % 55 % 14 % 11 % 8 % VtxStatus Distributions MC AllGamma 2 Towers all cuts no cuts 162 0 and 1 2.7 % of initial triggers!

  26. 1 162 0 162 34 128 86 % 6 % 3 % 59 % 13 % 7 % ...and with DATA DATA Cosmic rays 2 Towers no cuts all cuts 162 0 and 1 0.6 % of initial triggers!

  27. My friend 162 g dir g dir hit W hit SI SI tracks tracks VtxStatus = 162 2 tracks vertex, vertex tracks share first hit and DOCA point lies inside track hits

  28. Energy distribution MC AllGamma 2 Towers DATA 2 Towers all cuts VtxStatus=162 all cuts VtxStatus=162 TkrNumTracks>0 CalEnergySum>10. VtxAngle>0. Tkr1TotFirst>1 Tkr1SSDVeto>1 Tkr1ToTTrAve>1.3 VtxStatus=162

  29. Summary • Developed a simple algorithm to select g in cosmic ray data using Bill’s analysis as a starting point • Learned about how different the g topologies are from the simple picture from pair conversion • Future Work:  Possibility to use the selected g sample to study the behaviour of the detector with different register configurations  Depending on the physics analysis, we may be more interested in selected vertex topologies • Explore this further in my thesis • Analysis of reprocessed 4, 6 and 8 towers in progress...

  30. GRAZIE... • Eduardo • Bill • Francesco • Anders • Leon • Eric • Luis ...all other italian summer students and people I met at SLAC!

  31. Backup slides

  32. 6 Towers Results

  33. 6 Towers Results

  34. 4 Towers Results

  35. 4 Towers Results

  36. 6 Towers Results 100 % 10 % 1 % 0.1 % AllGamma Muons 11.5 Data 75 Data 77 1.9 0.18 STEPS 1 2 3 4 5

  37. 4 Towers Results 100 % 10 % 1 % 0.1 % AllGamma 9.9 Muons Data 2.5 0.1 STEPS 1 2 3 4 5

  38. Same with MC Muons... MC Surface Muons no cuts 0 and 1 1 0 92 % 3 %

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