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IC22 extraterrestrial cascades search unblinding proposal Joanna Kiryluk, LBNL 05/06/2009

IC22 extraterrestrial cascades search unblinding proposal Joanna Kiryluk, LBNL 05/06/2009. Filtering && Data and Monte Carlo comparisons Extraterrestrial Flux Sensitivities Summary + 4. Backup slides. 1. Event Selection (shown previously). Cascade Pole Filter:

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IC22 extraterrestrial cascades search unblinding proposal Joanna Kiryluk, LBNL 05/06/2009

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  1. IC22 extraterrestrial cascades search • unblinding proposal • Joanna Kiryluk, LBNL • 05/06/2009 Filtering && Data and Monte Carlo comparisons Extraterrestrial Flux Sensitivities Summary + 4. Backup slides 1

  2. Event Selection (shown previously) • Cascade Pole Filter: • LineFit Velocity < 0.25 and Tensor of Inertia Evalratio > 0.109 • Level3: Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2 • Level4: Contained events filter: Events must start inside a fiducial volume • Level5+6 Cleaning tails …. Level2 Data Burn 2 Level 2-6 Cuts description && more details in backup slides pages: 25-45

  3. Background reduction vs cut level - Summary Bg/Signal trigger L2 L4 L6 1 Cut Level After Level6: N(Bg)/N(Signal) ~ 103 N(Signal) ~ 160 events in 240 days (E-2) 3

  4. Cascade Filter levels comparison: Data vs MC Level 2 Level4 Level6 NChannels Excess in data Level>=4: running out of bg MC statistics 4

  5. Cascade Filter levels comparison: Data vs MC Level 2 Level4 Level6 COGX Cascade Pole Filter Rates [Hz] COGY Shapes (COGX and COGY) ~ consistent 5

  6. Cascade Filter : Data vs MC (1) Cascade Filter levels comparison: Data vs MC Level 2 Level4 Level6 COGZ Data/MC Rate problem: above AND below dust layer 6

  7. Data/Corsika Rates Ratio vs cut level 1 Trigger Cascade PoleFilter Cut Level After Level6: Factor of ~3 discrepancy between Corsika and experimental rates (bg rate ~10-2 Hz) 7

  8. Level7: Background reduction using hit topology: Fill-ratio (Doug Rutledge’s module) • distribution of distance between hit DOM and reconstructed vertex (for each event) MeanDistance x CscdLlhVertex Mean • fill-ratio= Nr of Hit Doms / Nr of All Doms within a sphere Center= CscdLlhVertex Example: Fill-ratio=2/10 = 0.2 R=2*MeanDistance x 8 Bad DOMs excluded

  9. Fill-Ratio vs SphereRadius (Level7): Data vs MC NuE Level7 cut Above dust layer Corsika Data 10% NuE Level7 cut Below dust layer Corsika Data 10% Agreement between data and bg MC in shape above dust layer, Different shape in data and corsika below dust layer: Depth dependent cuts based on Data! 9

  10. Background reduction vs cut level - Summary Bg/Signal 1 • No data @Level 7 • 2 corsika events@Level7 Cut Level 10

  11. After Level7 && NCh>50 : • 56 signal events For 240 days • 2 events corsika (corresponds to 10+2.8=13 events in 240 days) • No data Example of surviving corsika event 11

  12. Energy Reconstruction: final cut (Level8) CscdLlh energy reconstruction settings: S. Lafebre && B. Fox (PSU) NuE Bottom Top Log(RecoEn) Log(TrueEn) - Log(RecoEn) Two distributions: depth dependence not build-in to pandel phit-nohit (uses Bulk ice). Thus cannot cut on RecoEnergy without making a depth dependent correction ~ +/-0.4 12

  13. Before RecoEnergy Correction After RecoEnergy Correction Above dust layer NuE RecoEn NuE TrueEn Below dust layer 13

  14. MC 182 TeV e Level8 cut: Log(RecoEn_corrected)>4.2 - not optimized, due to limited bg MC statistics After final (Level8) cut, 0 events from the burn sample and corsika remain Signal e (True)Energy distribution after final (Level8) cuts Below dust layer: Above dust layer: Mean=5.26 Mean=5.23 Log(TrueEnergy) Log(TrueEnergy) • Uniform energy range for top and bottom parts of the detector 14

  15. Position and Energy resolutions After Level8 cut on log(E_reco) 15

  16. Energy Resolution (Level8) Below dust: Rms=0.31 Log(TrueEn) - Log(RecoEn) Log(TrueEn) - Log(RecoEn) Log(TrueEn) Above dust: Rms=0.26 Log(TrueEn) - Log(RecoEn) 16 Log(TrueEn) Log(TrueEn) -Log(RecoEn)

  17. Position resolutions at L8 (NuE MC) for CscdLlhVertex TrueX-RecoX TrueY-RecoY TrueZ-RecoZ 17

  18. Expected event upper limit And flux limit after unblinding For unblinding we propose to use all the cuts ( Level <=8 ) 18

  19. Event upper limit 240 days of livetime and CL=90% Conservative limit! [ Used e.g. in HEP experiments to set limits on rare decays branching ratios ] <mu90> for bg=10 <mu90> for bg=0.0 • If much better bg MC statistics were available then we could estimate bg precisely and do bg subtraction to get a better limit (Fieldman-Cousins) • Since we don’t have enough MC, we can assume all observed events (after unblinding) are signal and set an upper limit for the mean of Poisson variable given N_observed events in the absence of background [1-CL=Sum_0^Nobs Px(n) ] 19

  20. MRF to estimate flux limit expectations after unblinding <mu90>/nsignal for bg=10 <mu90>/nsignal for bg=0.0 • E2xlimit =MRFx10-6 [GeV s-1 sr-1 cm-2] • E2xlimit range: 7 x (10-8 - 10-7)[GeV s-1 sr-1 cm-2] (conservative limit ) • assuming n_observed events < 20 after unblinding • range depends on n_observed after unblinding • If much better MC statistics were available then we could do bg subtraction to get a better limit - but we don’t. Use limit assuming no bg. • “problem” if significantly more events observed after unblinding 20

  21. Summary Data and MC rate discrepancy: increases with cut level. Shapes agree better than rates, bigger discrepancy below dust level (e.g. fill-ratio) Final cuts based on data (burn sample), but also on (a few) bg MC events with long-er effective lifetime than data (insufficient bg Monte Carlo statistics) Will use a conservative method to estimate flux limit assuming no background contribution (no precise estimate of background contribution thus no background subtraction method) 3. Final energy range: ~20 TeV to ~1PeV (Mean ~ 160 TeV) Expected results after unblinding: E2xlimitrange: 7 x (10-8 - 10-7) [GeV s-1 sr-1 cm-2] if n_observed < 20 after unblinding [ Flux limit will depend on number of observed events after all cuts after unblinding. Problem if “large” number of events observed] ICRC writeup (analysis description) available on the wiki page: http://wiki.icecube.wisc.edu/index.php/Papers_for_ICRC-2009 Ready to unblind 21

  22. BACKUP SLIDES

  23. Data and MC Samples Data - burn sample (24 days) 2. Monte Carlo samples: a) Signal: electron neutrino: - dataset 1736 and 1739 NuGen E-2 spectrum, log10(E)= 1.6 - 10.0 Total = 3.5 M IC22 triggered events b) Background MC - Corsika (single muon) dataset 1540 (unweighted) dataset 1541 (weighted) Total= 280 M IC22 triggered events - Corsika (coincident muon) dataset 1567 (unweighted) - Corsika (tri-coincident muon) dataset 1569 (unweighted) much smaller samples: 1.8M IC22 triggered events / set 100k files generated Huge effort, production @multiple sites

  24. Trigger and PoleCascadeFilter rates Experimental rates taken from the Monitoring page Rate [Hz] • Trigger rate: temperature variation Data: 515 Hz to 615 Hz MC: 565 Hz Data/MC Agreement • CascadeFilter rate: Data: 18 Hz to 22 Hz MC: 14 Hz Data/MC ~ 1.3 -1.6 • CascadeFilter/Trigger rate ratio: Data: 0.032-0.036 (stable) MC: 0.025 InIce SMT trigger 07/01/07 03/16/08 Rate [Hz] PoleCascade filter Time [Mjd]

  25. Cascade Pole Filter: data vs MC P. Toale && M. D’Agostino filter proposal: LineFit Velocity < 0.25 and Tensor of Inertia Evalratio > 0.109 LineFit velocity ToI evalratio L2/Trigger Bg reduction = 0.025 Signal fraction = 0.71

  26. Cascade Filter (Level3 FINAL): Data vs MC • Common cut for atmospheric and extraterrestrial analyse Module CscdL2Filter (Michelangelo D’Agostino UCB) Zenith>1.27 && (TrackLlh logl - CscdLlhVertex negLlh) > -16.2 • This is a loose cut for extraterrestrial analysis

  27. Level3 optimalization for Extraterrestrial analysis Later it was decided to use looser cuts And keep the same i3 files for atmospheric And extraterrestrial analyses

  28. Zenith [rad] RllhTrack / RllhCscd Cascade Filter Level2: Data vs MC (5) • Reconstruction results from TrackLlh and CscdLlh algorithms • Corsika (single muons): Events with Zenith>1.4 rad are misreconstructed downgoing “leading” muons • Data: Excess of ‘cascade-like’ events with small values of reconstructed Zenith angle and small values of RllhTrack/RllhCscd are for COGZ at the bottom of IC22

  29. Data (run=109831) Corsika background Signal e Zenith RllhTrack / RllhCscd Level3 Cuts: Reconstruction Results at Level2 • TrackLlh Zenith vs RllhTrack/RllhCscd

  30. Level3 cuts optimalisation • Sqrt(N_bg) / N_Signal vs Zenith Cut in RllhRatio bins: RllhRatio= 1.025 RllhRatio= 0.9 RllhRatio= 1.0 RllhRatio= 0.8 0.8 1.4 1.7 Zenith Cut [rad] N_Signal / sqrt(N_bg) maximum for: Zenith> 1.4 rad and RllhRatio > 1.0 (proposed cuts for this analysis at level3)

  31. Extraterrestrial e: Level3 Cuts Optimalisation 4 TeV Find the best combination of cuts on Zenith and RllhTrack/RllhCscd by minimizing sqrt(N_bg)/N_sig (using Monte Carlo only) assuming 240 days of livetime and signal flux(es) = 1.0 x 10-6(7) E-2 . Result: Level3 cut = Zenith> 1.4 rad && RllhTrack/RllhCscd > 1.0 1.0x10^6 E-2 flux N_sig(Level3) N_sig(Level2)

  32. Event display: Level2 Cascade Filter events 2 example events from run=109831(real data) NCh= 293 Nstrings= 19 Reco: TrackLlh Zenith= 0.59 rad Rllh-track/Rllh-cscd ratio= 0.71 NCh= 57 Nstrings= 8 Reco: TrackLlh Zenith= 0.62 rad Rllh-track/Rllh-cscd ratio= 0.83

  33. Cascade Filter Level3 proposed cut: Data vs MC After Level3 cuts Cascade Pole Filter Improvement in Rate vs COGZ (Corsika and Data)

  34. Cascade Filter Level3 proposed cut: Data vs MC Cascade Pole Filter After Level3 cuts Improvement in #channels distribution (Corsika and Data)

  35. Cascade Filter (Level4): contained event filter (data) ContainedFilterModule (Steve Movit PSU) • Events must start inside Fiducial volume Level2 Data Burn + 8 DOMs top layer of the detector

  36. Cascade Filter (Level4): contained event filter (signal MC) Before (Level3) and After (Level4) contained Filter Log10(MCPrimaryEnergy) TruePosX Log10(MCPrimaryEnergy) Geometrical effect: For cascades inside fiductial volume filter efficiency is 100% Filter most efficient at lowest energies L4/L2 Bg reduction = 0.012 Signal fraction = 0.13

  37. PosX distributions in PosY bins Sum

  38. Extraterrestrial e: Summary of Statistics (MC) @Trigger Level , Cascade Filter Level and Analysis-Level4 Assumed: Livetime= 240 days and signal flux = 1.0 x 10-6 E-2

  39. T1 T2 Cascade Filter (Level5): Data vs MC (1) long tail Up to 60 s T1-T2[ns] NChannel =152 T1-T2=13 s Cut=5 s Run=109930 3-muon event First hit from the earliest muon starts in the middle of the detector, thus passing contained filter cut

  40. Cascade Filter (Level5): Data vs MC (2) • Zenith>1.2rad downgoing muons • 32-iteration track reconstruction • Zenith>1.2rad Bg: Misreconstructed downgoing muon • Nchannels NCh>=20 (loose cut) L5/L4 Bg reduction = 0.07 Signal fraction = 0.69 running out of MC statistics

  41. Level 5b) downgoing muons Zenith angle cut 32-iteration track reconstruction • Zenith>1.2rad for (Single) Corsika: • Misreconstructed downgoing muons • (96% of L5a NuE events survive)

  42. Examples of ‘Cascade’ like events with highest Nchannel multiplicity at Level5

  43. After Level5

  44. Cascade Filter (Level6): Data vs MC (1) • Reconstructed Cascade vertex and COGX (COGY) less than 60 m apart: X Y

  45. Cascade Filter (Level6): Data vs MC (2) • Time(FirstTrack)-Track(Secondtrack) > -1000ns • (Double muon reconstruction) • Reduced Llh Track/Cascade > 0.95 L6/L5 Bg reduction = 0.37 Signal fraction = 0.98 CscdReducedLlh=(negLlh/(nHits + unHitContribution - freeParams));

  46. ToI evalratio LineFit velocity COGZ COGX COGY Variables not usable for further cuts After Level7&&NCh>50: tightening the cuts • 56 signal events For 240 days • 2 events corsika (corresponds to 10+2.8 evts 240d ) • No data

  47. After Level7&&NCh>50: tightening the cuts After Level7 - tightening the cuts NStrings NCh • 56 signal events For 240 days • 2 events corsika (corresponds to 10+2.8 evts 240d ) • No data Llh Diff EventLength Variables not usable for futher cuts

  48. Extraterrestrial e: Summary of Statistics (MC)@ L4,L5 and L6 Assumed: Livetime= 240 days and signal flux = 1.0 x 10-6 E-2 MC underestimate rates: Factor of 2 (3) at L4 (6) L7&&L8 Insufficient MC Large uncertainties

  49. ‘Baloon’ events (at Level2) • small fraction observed mostly at the top part • of the detector (not x-y symmetric!) • - removed by fiducial volume cuts

  50. Cascade Filter Level2: Total charge per Dom vs depth Shown at the Spring 2008 Collaboration meeting String 73 String 73 Dom# 6 Dom# 7 Depth dependence! <Q> [p.e.] Dom# Q [p.e.] String 39 String 39 Dom# 6 Dom# 7 <Q> [p.e.] Q [p.e.] Dom#

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