IceCubeによる超高エネルギー宇宙ニュートリノ探索
Status and Future Prospects

Aya Ishihara for the IceCube collaboration
JSPS Research Fellow at Chiba University
第２４回宇宙ニュートリノ研究会

Outline• IceCubeにおける超高エネルギーニュートリノ探索• 超高エネルギーニュートリノ探索解析手法の現状と結果• 現在、進められている最新データ解析に向けた新しい手法の開発・今後の展開

IceCube at South Pole

1km3 volume80+6 Holes

60 Optical Modules

17 m between modules

125 m between holes

Construction
Finished!!

Astronomical Neutrino Sources
high energy cosmic-ray sources, e.g. AGN, GRB…

Cosmic accelerator
photonCMB

star-light

Bp + g  D+  p + p0  p + g gCosmicrayp + g  D+  n + p+  n + m + nNeutrino

The sources of the highest energy neutrinos
EHE cosmic-ray and CMB induced neutrinos
p >100EeVp+p0nm

nmm+nepg 2.7 K  p  + X  m  +n  e +n ' se+

The main energy range: En ~ 109-10 GeV

Gorhamモデルエネルギー領域

Neutrinos from CR sources
GZK neutrinos

IceCube Event Gallery
Cherenkov light illuminations from particles
With 40 strings, 2008 Dec

With 79 strings, 2010 June

With 22 strings 2007

130TeV
Cascade-likeEnergy threshold ~10 GeV>108 muons/day>200 neutrinos/day

With 40 strings, 2009 May

Directions in IceCube:
particle screening and the energy upper boundCRdown-going

mEHE nm• Neutrinos identified as“through the Earth” up-going
events but only upto < PeV

m,tm,tm

Northng• EHE neutrino-induced eventsare coming from above andnear horizontal directionm

nm > PeVup-goingnm < 1PeV

EHE neutrino mean free pathln ~ 100 km << REarthsccnN ~ 10-6~-4 mb

IceCube事象分類• 事象の方向– Upward-going neutrinos• Conventional atmospheric neutrino background• Prompt neutrinos + astrophysical neutrinos• Directional reconstruction is important – initiated by only neutrino
induced muon sensitive analysis• 事象のエネルギー– All direction– High energy– All Flavor• 事象のトポロジー– All direction– Flavor sensitiveExtremly-high Energy Neutrino Signal

downup

mdE
Edx

GZK m
GZK t
Atmospheric m

108 muons/day

2-3 GZK events/yearAnalysis Flowfor 2008-2009 data with the half IceCube• Level-0 Online filter data reduction• Level-1 appropriate sets of MCs/Data samples• MCs are high energy optimized• Level-2 Quality cut• Less systematics• Detailed MC/Data comparisons• Level-3 Final selection

Level-1: Samples

Total livetime 370days

promising GZK neutrinos = high NPE horizontal events

Data
BG MC
Sig MC-4400nsec < time relative to thelargest NPE time < +6400nsec

Number of DOM

The Largest NPE DOM (LND)

pulse timing relative to LND time[nsec]

Level-2 Quality cut
promising GZK neutrinos = high NPE horizontal events

MCpulse depth [m]zLND

Datashallowcos(ZA)pulse timing relative to LND time [nsec]

deepPulse timing indicates the signal-like-ness
Earlier pulses relative to LND time

eventLengt h  tLND - t 1stdHt1stHorizontal short length
Vertical  long lengthdL
The Largest NPE DOM
Prompt pulses relative to LND timetLND

Data and Mcs at Level-2
shallow:

Data (BTW)
BG MC
Sig MClog (NPE BTW)

log (NPE BTW)

deep:cos(za BTW)

E-LND time [nsec]

Level-3 Final Selection
promising GZK neutrinos = high NPE horizontal eventsBG

shallow experimentalcos(za)SIGNALshallow

shallow

E-LND time [nsec]

log (NPE)

deep experimental

deep

deeplog (NPE)Summary of analysis
Level-0

Online filtering level – log NPE > 2.8

Level-1

Coincidence pulse cleaning,
MC applicability: Nch > 200 && log NPE > 3.5

Level-2

Horizontally mis-reco event cleaning for shallow and timing
distributions for deep events

Level-3

Final Candidate Selection Criteria

Error Budget
Signal (GZK1)
0.8 %(stat.)+14.0 -11.6 %(sys.)
Err. Sources
statistical error
NPEmeasurementin-situ calib.
-18.5%
in-lab calib.
10.1%)

Signal (GZK model)
0.8 %+3.89 / -7.22 %neutrino crosssection

9.0 %photo-nuclear
interaction+10.0 %

LPM effect

1.0 %Background
17.0% (stat.)+60.4 % -96.0%(sys.)
Err. Sources
statistical error

Background17.0 %

Composition-83.86%

interaction model+36.1%

Coincident event(cos theta>0.2)+29.4%

Coincident event(cos theta<0.2)+10.5%

ice property+30.2% / - 22.2%

NPE
measurements+37.1% / -46.7%

Diffuse neutrinos with extremely-high energies
E-2 flux upper limit in 106.3 < Energy/GeV < 109.8333.4 days upper limit with only the half detector
GeV g flux limit by Fermi

PRELIMINARY*Yoshida et al The ApJ 479 547-559 (1997), **Kalahsev et al , Phys.Rev.Rev. D 66 063004 (2002), ***Engel et al, Phys. Rev. D, 64(9):093010, 2001, ****Ahlers et al,Astropart. Phys. 34 106-115 (2010) #Yoshida et al, Phys.Rev.Lett. 81 5505 (1998),##Sigl et al , Phys.Rev.Rev. D 59 043504 (1998), ^Razzaque et al(2003)

Near Future Sensitivity
PreliminaryIceCube Upper limit~2009/5

Full scale sensitivity(MC)Expected EHE signal event rates
The full IceCube# of events(3 years)

The half IceCube# of events

ModelsGZK1 (Yoshida et al) *

0.57

3.1

GZK2 Strong Evol. (Sigl) **0.91 (C.L 53.4%)

4.9

GZK3 (ESS with WL=0.0) ***

0.29

1.5

GZK4 (ESS with WL=0.7) ***

0.47

2.5

GZK5 (Ahlers max) ****

0.89 (C.L 52.8%)

4.8

GZK6 (Ahlers best fit) ****

0.43

2.3

Z-Burst #1.03 (C.L 55.7%)

5.1

Top Down(SUSY) ##5.68 (C.L 99.6%)

31.6

Top Down(QCD) ###1.19 (C.L 66.4%)

6.3

W&B(evol) ^

3.7

24.5

W&B(no evol) ^

1.1

5.5

*Yoshida et al The ApJ 479 547-559 (1997), **Kalahsev et al , Phys.Rev.Rev. D 66 063004 (2002), ***Engel et al, Phys. Rev. D, 64(9):093010, 2001, ****Ahlers et al,Astropart. Phys. 34 106-115 (2010) #Yoshida et al, Phys.Rev.Lett. 81 5505 (1998),##Sigl et al , Phys.Rev.Rev. D 59 043504 (1998), ^Razzaque et al(2003)

Flavor and Angle Dependence
Effective Area [m2]
nu_e

nu_mu

Event rates
nu_tauIceCube Sees Wide Energy Range

PRELIMINARY

Future implementation 1: IceTop SLC Veto

Jan Auffenberg and Shirit CohenFuture implementation2: Bundles, outlying muons & moreand Event Topology

Patrick
Berghausand@ Annapolis
25
PatricBerghaus
Shirit CohenOutlook• 2008-2009データによる、EHE ニュートリノ解析によってIceCubeにおけるGZKニュートリノ探索のベースラインは確立。（DraftはFinal Collaboration review中、来週中にはペーパーSubmitします）• 2009-2010年度データ解析中（ICRC2011）– 2008-2010 Combinedデータで現在のリミットの1/2• 2010-2011年度データ解析にむけた新しいBG vetoの手法の開発中（ICRC2011）• 2008年4月から2012年5月までのCombinedデータ解析（FullIceCube 3年分相当）でGZKモデルの議論が可能！
New pictures of the Universe shooting at South Polewith the full IceCube detector coming soon!

The IceCube Collaboration
Germany:

Sweden:USA:
Bartol Research Institute, Delaware
University of California, Berkeley
University of California, Irvine
Pennsylvania State University
Clark-Atlanta University
Ohio State University
Georgia Tech
University of Maryland
University of Alabama, Tuscaloosa
University of Wisconsin-Madison
University of Wisconsin-River Falls
Lawrence Berkeley National Lab.
University of Kansas
Southern University and A&M
College, Baton Rouge
University of Alaska, AnchorageUppsala Universitet
Stockholm Universitet

UK:
Oxford University

Switzerland:
EPFL

DESY-Zeuthen
Universität Mainz
Universität Dortmund
Universität Wuppertal
Humboldt Universität
MPI Heidelberg
RWTH Aachen

Belgium:
Université Libre de Bruxelles
Vrije Universiteit Brussel
Universiteit Gent
Université de Mons-HainautJapan:
Chiba University

New Zealand:
University of Canterbury

33 institutions, ~250 members
http://icecube.wisc.edu