EHE Neutrino Search with the IceCube Aya Ishihara The University of Wisconsin - Madison for the EHE Verification working group

Outline Expected the highest energy region signal neutrinos How they might look like from the point of IceCube detector Results from MC simulation analysis with full and this year’s configuration Outlook toward real data analysis with 9 strings

Recent Activities by EHE Working Group Convener: Shigeru Y. Muon Reconstruction: Sean G., Keiichi M., David B. Tau Reconstruction: Rodin P. MC study: Shigeru, Kotoyo H., Aya I. MC (semi-) mass production: Paolo D., Keiichi Data check: Hiroko M., Kotoyo, Aya See Shigeru’s analysis session on Thursday

Extremely High Energy Neutrino Possible Signals… Standard scenarios Ex. GZK mechanism – EHE cosmic-ray induced neutrinos ( E ~ GeV ) Exotic scenarios Ex. Top-Down – decays/interaction of massive particles ( E ~ GeV )

EHE Neutrino with km 3 Detector (I) Where to look for events? Filtering from large background - Atmospheric  distinguishable by their energy Need good energy resolution EHE neutrino mean free path ~ 100 km << R Earth down-going up-going EHE neutrino events are down-going Not up-going

EHE Neutrino with km 3 Detector (II) How do they look like? Series of cascade Energy deposit indicates the primary particle energy e+e-e+e-    pair-creation bremsstrahlung photo-nuclear

IceCube EHE Event Channels Possible EHE particles in depth Atm    Secondary  and  E GZK >> E Atm  Fluxes at the IceCube depth

MC Simulation Setup Event Samples Muon events with E -1 spectra 95,000 events Muon events with E -2 spectra 110,000 events Tau events with E -1 spectra 99,000 events 10 5 GeV ~ GeV

Simple Primary Energy Indicator Estimated total number of photo-electrons per event  Contained Uncontained Contained Uncontained 

How NPE is Estimated from Waveforms (I) Log 10 ( ATWD estimated NPE ) Estimated number of photo-electrons per DOM ATWD or FADC? Log 10 (FADC based estimated NPE ) Log 10 (ATWD based estimated NPE ) Log 10 ( FADC estimated NPE) Log 10 (MC Truth NPE ) Red: DOM of which ATWD charge is larger Blue: DOM FADC is larger Integrated charge over a waveform divided by single pe charge

How NPE is Estimated from Waveforms (II) MC Truth NPE vs. Larger Charge waveform based estimated NPE per DOM Log 10 (MC Truth NPE ) Log 10 ( Best estimated NPE ) This, “use the larger charge waveform”, in principle applies also for the finer waveform based reco

Signal vs. Background: Energy/event-sum NPE GZK  Atmospheric  GZK  Contained events only

Event Rate without Background Cut GZK  GZK  Atmospheric  GZK  GZK  Atmospheric  Zenith angle NPE up down

Signal Domain: Zenith/NPE GZK  Atmospheric 

Event Rate in Signal Domain GZK  3.5 events/year GZK  0.56  events/year Atmospheric  0.33 events/year GZK  GZK  Atmospheric  GZK  GZK  Atmospheric 

Event Rate based on simple reconstruction GZK  GZK  Atmospheric  GZK  GZK  Atmospheric 

Event Rate with 9-strings GZK  0.67 events/year Atmospheric  events/year GZK  Atmospheric  GZK  Atmospheric  AMANDA IceCube

For taus… GZK  Atmospheric  Assuming we have extremely good geometrical reconstruction,

Event Rate with the optimistic cut GZK  GZK  Atmospheric  GZK  GZK  Atmospheric 

Muon Effective Area – Full String Black (up-going): -1.0 < cos(  MC ) < -0.8 Red: -0.6 cos(  MC ) < -0.4 Blue (horizontal, slightly up-going) -0.2 < cos(  MC ) < 0.0 Pink: 0.4 < cos(  MC ) < 0.6 Green (down-going): 0.8 < cos(  MC ) < 1.0

Effective Area – 9 strings ~10 % strings are much more than 10 % as an effective area ! Black (up-going): -1.0 < cos(  MC ) < -0.8 Red: -0.6 cos(  MC ) < -0.4 Blue (horizontal, slightly up-going) -0.2 < cos(  MC ) < 0.0 Pink: 0.4 < cos(  MC ) < 0.6 Green (down-going): 0.8 < cos(  MC ) < 1.0

Summary and Outlook IceCube is indeed capable of detecting EHE neutrinos with both full and this year’s 9-string configuration First-level background filtering can be done with very simple parameters such as NPE-sum, zenith Further understandings of detector performance Comparison between real data and MC simulation Energy and geometrical reconstructions!!

Extra

N_DOM vs. NPE with 9 strings

April 11, 2006IceCube Collaboration Meeting25 Event Rate vs. Primary Energy

Predicted Fluxes

9-string Geo

The IceCube Detector