EHE Neutrino Search with the IceCube

Aya IshiharaAya IshiharaThe University of Wisconsin - MadisonThe University of Wisconsin - Madisonfor the EHE Verification working groupfor 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 talk @ analysis session on Thursday

Extremely High Energy Neutrino

Possible Signals… Standard scenariosEx. GZK mechanism – EHE cosmic-ray induced neutrinos

( E ~ 109-10 GeV )

Exotic scenariosEx. Top-Down – decays/interaction of massive particles

( E ~ 1011-15 GeV )

seXp K '7.2

xM

EHE Neutrino with km3 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 << REarth

down-going

up-going

EHE neutrino events are down-goingNot up-going

EHE Neutrino with km3 Detector (II)

How do they look like?

Series of cascade

Energy deposit indicates the primary particle energy

e+e-

pair-creation

bremsstrahlung

photo-nuclear

IceCube EHE Event Channels

Possible EHE particles in depth

Atm

Secondary and

EGZK >> EAtm

Fluxes at the IceCube depth

MC Simulation SetupEvent 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 105 GeV ~ 1011 GeV

Simple Primary Energy Indicator

Estimated total number of photo-electrons per event

ContainedUncontained

ContainedUncontained

How NPE is Estimated from Waveforms (I)

Log

10 (A

TW

D e

stim

ated

NP

E)

Estimated number of photo-electrons per DOM

ATWD or FADC?

Log

10 (F

AD

C b

ased

est

imat

ed N

PE

)

Log10 (ATWD based estimated NPE)

L

og10

(FA

DC

est

imat

ed N

PE

)

Log10 (MC Truth NPE) Log10 (MC Truth NPE)

Red: DOM of which ATWD charge is largerBlue: DOM FADC is larger

Integrated charge over a waveformdivided by single pe charge

How NPE is Estimated from Waveforms (II)

MC Truth NPE vs. Larger Charge waveform based estimated NPEper DOM

Log10 (MC Truth NPE)

Log

10 (

Bes

t es

tim

ated

NP

E)

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

GZKGZK

Atmospheric

GZKGZK

Atmospheric

Zenith angleNPE

up down

Signal Domain: Zenith/NPE

GZK Atmospheric

Event Rate in Signal Domain

GZK 3.5 events/year

GZK 0.56events/year

Atmospheric 0.33 events/year

GZKGZK

Atmospheric

GZKGZK

Atmospheric

Event Rate based on simple reconstruction

GZKGZK

Atmospheric

GZKGZK

Atmospheric

Event Rate with 9-strings

GZK 0.67 events/year

Atmospheric 0.0085 events/year

GZKAtmospheric

GZKAtmospheric

AMANDA

IceCube

For taus…

GZK Atmospheric

Assuming we have extremely good geometrical reconstruction,

Event Rate with the optimistic cut

GZKGZK

Atmospheric

GZKGZK

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, 2006 IceCube Collaboration Meeting

25

Event Rate vs. Primary Energy

Predicted Fluxes

9-string Geo

The IceCube Detector