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Aya Ishihara for the IceCube EHE pwg

1. A quest for EHE neutrinos with the IceCube detector proposal for EHE neutrino search in 2006 - 9 string sample. Aya Ishihara for the IceCube EHE pwg. 2. Introduction. Target Neutrinos of this analysis. Target Target Energy Range Log(E/GeV) > 8 Optimized for GZK neutrino.

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Aya Ishihara for the IceCube EHE pwg

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  1. 1 A quest for EHE neutrinoswith the IceCube detectorproposal for EHE neutrino search in 2006 - 9 string sample Aya Ishihara for the IceCube EHE pwg

  2. 2 Introduction

  3. Target Neutrinos of this analysis Target Target Energy Range Log(E/GeV) > 8 Optimized for GZK neutrino GZK neutrino • The standard scenario of EHE cosmic-ray induced neutrinos • The main energy range: • En ~ 109-11 GeV nm m p EHE-CR nm ne e

  4. CR m EHE n m,t m n e,t,m EHE n e e,t e m m,t Competitors: On-going EHE Neutrino Search (GZK neutrino energy range 108~11 GeV) Underground Ice Cherenkov Detector : IceCube Main BG rejection based on energy estimation Simple and robust Background: Atmospheric muon Air-shower Detector HiRes, Auger BG rejection based on near-horizon/upgoing young shower reconstruction MC studies claim the target sensitivity of Auger/HiRes are almost the same as IceCube, although they are not neutrino detector! No public results from 3 experiments yet. All claims result is coming very soon.

  5. EHE Neutrino Underground However, Structure of atmospheric muon flux above 106GeV is very uncertain ! Surface Fluxes Fluxes at the IceCube depth tentative atm m main signal GZK neutrino induced leptons background Atmospheric muon Simple energy cut works! tentative EGZK >> EAtmm !! S. Yoshida et. al. (2004) Phys. Rev. D 69 103004

  6. Orders difference EHE regime How uncertain ? muon background in very high energy regime: NOT well-known (highly dependent on parton distribution assumption), e.g. charm production bundle structure Atmospheric muon Model fluxes From charmed meson decay nm m

  7. Need models which describe our real data in UHE background regime Empirical model

  8. Analysis

  9. Analyzed 9-stringreal sample2006statistics Physics runs since 2nd June, 2006 to 20th, Nov, 2006 124.148 days of livetime after file selection (a list of files not used and used in this analysis can be found at analysis web page) 0.134 Hz for Channel N > 80 After file cleaning Event Frequency Before file cleaning Hz Channel N >53 Event interval Event interval • stable filtering condition for EHE sample with Nch>80

  10. The 9-stringreal sample2006Example Bright Events

  11. The 9-stringreal sample2006FADC Waveforms (integral ~ NPE) 90 mV DOM#31 1 ms Saturated ~ 90mV

  12. Typical ATWD EHEWaveforms (integral ~ NPE) DOM#36 DOM#37 DOM#26 DOM#27 DOM#28 DOM#29 105 ns 402 ns DOM#34 DOM#30 DOM#33 DOM#31 120 mV DOM#32 DOM#35

  13. Looking at a Very Typical Combined EHE Waveform String#29 – DOM#8 RunID 89761- Event ID 1477531 Ch0 Ch1 Ch2 105 ns 0 ns 402 ns 0ns 105 ns Combined ATWD FADC 1 ms 105 ns 402 ns

  14. m t The 9-string simulation:NPE and Energy Correlation Still have reasonable Energy vs. NPE correlation up to logNPE ~ 4.5 then, early saturation effect diffuse them

  15. ‘Reduced Bin#’reduced NPE NPE corresponds to signal region is quite reduced because of ‘reduced bin readout’ in 2006 data Signal NPE region based on full readout t Signal NPE region based on reduced readout simulation

  16. EHE region!! The 9-string real NPE distribution Very- high energy Background regime Channel N > 80 Filtering bias

  17. Cosmic-Ray m m Atmospheric Muon Bundles Model(see web page for further detail) cosmic-ray energy and total muon energy above Ethres in a bundle bundles of atmospheric m measured cosmic-ray flux muon bundle flux

  18. m Single m represents bundled m ? m m NPE distributions of Toy model bundled muon events (50 muons in 100 m radius, 2*106 GeV each) and from single muon (108 GeV) events in 100 m radius bundle single muon N channel Log10(event-sum NPE) Log10(channel wise NPE)

  19. 5.4 8.2 5.4 8.2 Log10(E bundle/GeV) Log10(E bundle/GeV) Atmospheric Model Construction Flux after ice propagation (E2dF/dE[GeV/sec str cm2]) Flux at sea level (E2dF/dE[GeV/sec str cm2]) down cos zenith zenith 0.0 0.75 0.0 0.75 horizontal

  20. In-ice fluxes with new model with GZK cutoff !! #2 #1 ET=14.5 GeV A=1

  21. NPE distribution comparison set #1 simulation and real Set # 1 -1.0<Cos fg-theta < 1.0 0.6<Cos fg-theta < 1.0 GZK m GZK t atmospheric m real data -1.0<Cos fg-theta < 0.4 0.4 < Cos fg-theta < 0.6 Log10(NPE)

  22. NPE distribution comparison set #2 simulation and real Set # 2 -1.0<Cos fg-theta < 1.0 0.6<Cos fg-theta < 1.0 GZK m GZK t atmospheric m real data 0.4<Cos fg-theta < 0.6 -1.0<Cos fg-theta < 0.4 Log10(NPE) Log10(NPE)

  23. Signal and BG Simulation: NPE vs. Cos(qlinefit) Atmospheric muon model Cos fg-theta Atmospheric muon model Log10(NPE)

  24. Event Selection Cut level 0 1 2 3 4 5 6 Cos fg-theta GZK m GZK t 7 8 9 10 11 12 Log10(NPE) Set # 2 Set # 1

  25. Event Passing Rate GZK m GZK t GZK m+GZK t atmospheric m set #1 atmospheric m set #2 zoom • Because of uncertainty from NPE/Energy relation, can not optimize the cut too aggressively • Cut #8 is selected

  26. Effective Area Filtering condition Channel Number > 80 Signal condition Cut #8 km2 km2

  27. Expected Sensitivity...long journey toward GZK to be continued… with cut #10 with cut #8 90 % C.L. TD ‘standard’ GZK flux Strong ev. GZK Z-burst

  28. Summary

  29. Ready to access EHE region! • The 9 strings provided analyzable data sample in 2006 • MC shows 9 string IceCube is capable of EHE neutrino search but early saturation and reduced bin numbers mainly has limited its capability • BG is estimated using empirical atmospheric muon bundle model • Simple cut gives an event rate of ~0.02 GZK events in 124 days and expected 10-3 background atmospheric events in the same interval. • 22 string independent sample will steadily confirm any finding in 9 string data including empirical atmospheric muon model • No more bin number reduction!!

  30. FAQ 1 • Q-1)CORSIKA? • A-1) Use of CORSIKA for this analysis is not realistic because of the lack of 1) reliable model (incl. bundle and prompt) in interested energy region at surface, 2) computational resources to obtain good stats at this energy and 3) very sensitive detector simulation for partially deployed partial DAQ operation to reproduce full NPE spectra

  31. FAQ 2 • Q-2)Energy resolution / standard-candle? • A-2) http://www.ppl.phys.chiba-u.jp/~aya/SC/gdom-1.html • MC gives ~ a factor of two more NPEs. This will be put into the systematic errors in finalizing the (unblinding) analysis. • Let us also remark that GZK spectrum is so hard that the shift of NPE (indirectly related to energy) threshold in the signal cut would not affect sensitivity in EeV regime too much.

  32. FAQ 3 • Q-3)Baseline for NPE calculation? • A-3) We have observed significant baseline shift/droop. Our recipe to fix it was determined by looking at the baseline distribution of SC data estimated by the various algorythm. • http://www.ppl.phys.chiba-u.jp/~aya/SC/index.html • Q-4)Contribution from GZK neutrino which make in-detector interaction? • A-4) There exists, but minor in the overall event rate (See S.Yoshida et al, PRD 69 (2003) 103004). We are, however, generating neutrino-induced events by JULIeT and the • event rate from the contained events are reported in the collaboration meeting.

  33. FAQ 4 • Q-5)IceTop to establish atmospheric muon bundle model? • A-5) It is in our future plan. Insight of the mass composition of Cosmic Rays will narrow the parameter space in the bundle model. We need more stats to realize this study.

  34. FAQ 5 • Q-6)Is this analysis interfere with high energy cascade search? • A-6) No. Our study is not aimed at cascade ID but just looking for very bright events. This analysis is nothing to do with the cascade-likelihood. A (minor) contribution from EHE cascade events are just added to those from muons and taus to estimate the overall event rate. Moreover, our signal energy range (EeV) is mostly higher than that in the mainstream cascade search where you lower the energy threshold by identifying the cascade-like event topology.

  35. FAQ 6 • Q-7)How the slight difference between bundle and our single muon representation in npe affects to this analysis? • A-7) It affects nothing. Our empirical formula has a flexibility in the relation between bundle energy (that determines NPE) and primary cosmic ray energy (that determines flux) • to make renormalization. The NPE/zenith angle distribution of the real data is well described by the model.

  36. Extra

  37. MC truth and LineFit q with Atm. Mu weight

  38. Angular Resolution Atm. Mu weight

  39. Memorandum for atmospheric muon fit using 9 string data

  40. Event Properties

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