Kotoyo Hoshinafor IceCube Collaboration

TAUP 2007 in Sendai

Diffuse high-energy neutrino searches in AMANDA-II and IceCube 9 strings

Event Detection Strategy Cosmic Ray

Cosmic RayAstrophysical

Neutrino (signal)

Muon

Atmospheric Neutrino

µνµπ +→ ++

µνν +++ee

(similar for )±− K,π

•Target neutrinos :

•Detect muons generated from neutrinos via Charged Current interaction

•Choose up going events to reject atmospheric muons(apply quality cuts)

θ

down going

up going

★

Ice

Cherenkov radiation

Digital Optical Module (DOM) for IceCube

Detection Mechanism

Observables

• Hit timing (Direct Hit, Hit)

• Number of Hit OMs (Nch)• Charge / waveform

Direct Hit

Hit

Used for track reconstruction,Number of Direct Hit (Ndir) indicates reconstruction quality

Used as energy estimatorwaveform can be used for trackreconstruction (not this analysis)

What is Diffuse Neutrino Search ?

• If individual neutrino sources are too faint...

• Still possible to investigate overall feature of isotropically distributed sources

• If astrophysical neutrinos follow harder energy spectrum than backgrounds...

Investigate energy-relatedobservable to search forastrophysical neutrinos!

Nch0 20 40 60 80 100

-110

1

10

210 Atmospheric Nu

Astrophysical Nu

)-2

(test flux: 1.0e-6 E

All Monte-Carlo

Energy[GeV])µ!(true 10

Log0 1 2 3 4 5 6 7 8 9

Arb

itra

ry U

nit

0

50

100

150

200

250

300

350

Atmospheric Nu

Astrophysical Nu

)-2

(test flux 1.0e-6 E

All Monte-Carlo

Analysis Strategy

Signal spectrum is harder than Atms.Neutrino

Nch

True NeutrinoEnergy Distribution

(not observable)

Number of Hit OMs (Nch)(observable)

count event aboveNch > Nchcut

i. Reject all background muons then Search best Nchcut

ii.Apply Nch cut (Nch>Nchcut) thencompare number of survived events with Monte-Carlo prediction

Nchcut

AMANDA-II807days multi-year

analysis 1500m

500m

200m

Data 2000 - 2003

!Uncertainty in atms.

!Barr et al. atms.

!Honda et al. atms.

!CORSIKA atms.

-1 sr-1 s-2 GeV cm-6 = 10sig"2E

Data 2000 - 2003

!Uncertainty in atms.

!Barr et al. atms.

!Honda et al. atms.

!CORSIKA atms.

-1 sr-1 s-2 GeV cm-6

= 10sig"2E

Data 2000 - 2003

!Uncertainty in atms.

!Barr et al. atms.

!Honda et al. atms.

!CORSIKA atms.

-1 sr-1 s-2 GeV cm-6 = 10sig"2E

Data 2000 - 2003

!Uncertainty in atms.

!Barr et al. atms.

!Honda et al. atms.

!CORSIKA atms.

-1 sr-1 s-2 GeV cm-6

= 10sig"2E

Cosine of Reconstructed Zenith Angle-1 -0.8 -0.6 -0.4 -0.2 -0

Even

ts

-210

-110

1

10

210

310

410

horizontal

events

removed

level of final analysis

level 5

Cosine of Reconstructed Zenith Angle-1 -0.8 -0.6 -0.4 -0.2 -0

Even

ts

-210

-110

1

10

210

310

410

• Require enough number of Direct Hit which close to the expected hit time for the reconstructed track (Ndir cut)

• Hits should distribute smoothly along with the reconstructed track

• Require long enough track

• Remove horizontal events

Event selection : Preparing neutrino induced eventsQuality cuts (examples)

upgoing horizontal

Data (Nch < 100)

AMANDA-II 807days Diffuse AnalysisNch distribution after final selection

)ch

Number of OMs hit (N

0 20 40 60 80 100 120 140 160

Even

ts

-210

-110

1

10

210

Data 2000 - 2003

!Uncertainty in atmospheric

! + prompt !Barr et al. atms.

! + prompt !Honda et al. atms. -1sr-1s-2 GeV cm

-6 = 1.0 x 10

signal"2E

-1sr-1s-2 GeV cm-8

= 7.4 x 10signal"2E

final event sample

rescaled!atms.

at Nch > 100, 6 events observedno significant excess from background

(GeV)]!

[E10

log3 4 5 6 7 8 9

]-1

sr

-1 s

-2 d

N/d

E [

GeV

cm

2E

-910

-810

-710

-610

-510

-410 data (prelim.)!!AMANDA-II 2000 atms.

! + prompt atms. !Barr et al. atms.

! + prompt atms. !Honda et al. atms.

!Max uncertainty in atms.

Frejus

MACRO

diffuse!!AMANDA B-10 1997

AMANDA-II 2000 Cascades (all-flavor / 3)*

AMANDA B-10 1997 UHE (all-flavor / 3)*

Baikal 1998 - 2002 ( all-flavor / 3 )*

RICE 1999-2005 ( all-flavor / 3 )*

AMANDA-II 2000 unfolding (prelim.)

AMANDA-II 2000-2002 UHE limit (prelim.)

limit!!AMANDA-II 2000-3

W&B limit/2 (transparent sources)

Full IceCube 1 yr

* assumes a 1:1:1 flavor ratio at Earth

AMANDA-II 807days Diffuse AnalysisUpper Limit

E-2 < 7.4 x 10-8 GeV cm-2 s-1 sr-1

Paper Published!Physical Review D 76,

042008 (2007)

IceCube 9 strings

137days analysis

-200

-100

0

100

200

200 300 400 500 600

xIceCube [m]

yIc

eC

ub

e [m

]

1

2

345

6 7

8

9 10

1112

13

14

15

16 17

18

19

21DL1

29

30

38 39

40SC1

49

50DL2

59

BC

~125m

IceCubeAmanda

/GeV)ν (E10

Log2 3 4 5 6 7 8

]2

are

a [

cm

νE

ffe

cti

ve

210

310

410

510

610

710

After final event selection

-0.8 > cos(true zenith) >= -1.0

-0.6 > cos(true zenith) >= -0.8

-0.4 > cos(true zenith) >= -0.6

-0.2 > cos(true zenith) >= -0.4

0.0 > cos(true zenith) >= -0.2

0.2 > cos(true zenith) >= 0.0

• 3~4 times larger detector volume • 3~4 times wider string intervals

IceCube 9 (IC9) vs AMANDA

Muon NeutrinoEffective Area(after Nch cut)

1km

250m 375m

500m

1m2

IC9Amanda

200m2~4 times larger effective area (105 ~ 106GeV)

90% energy range shifts to higher energy

Log10(primary Nu energy [GeV])2 3 4 5 6 7 8

-210

-110

1

10

210

310

410

Atms.Nu before Nch cut

Nu before Nch cut-21e-6xE

Atms.Nu after Nch cut

Nu after Nch cut-21e-6xE

90% signal region

True Neutrinoenergy

Amanda 90% signal reg.

CosZenith

-1 -0.8 -0.6 -0.4 -0.2 0 0.2

-110

1

10

210

CosZenith

-1 -0.8 -0.6 -0.4 -0.2 0 0.2

1

10

210

310

410

Event selection : Preparing neutrino induced eventsData Nch < 46 is already unblinded for Atms.Nu study

(see P.Desiati’s talk on Thursday)

Data + Atms. Mu+ Double Mu+ Atms. Nu+1e-6 E-2 Nu

after angle resolution cut

after Ndir cut after final cutCosZenith

-1 -0.8 -0.6 -0.4 -0.2 0 0.2

1

10

210

Number of event after final cut (Nch<46)

preliminary

Data : 52 eventAll background MC : 60 + 5 event

Nch distribution After final selection

Nch0 20 40 60 80 100 120 140 160 180 200

-110

1

10 Atms. Neutrino MC

Signal Neutrino MC

)-2

(test flux 1e-6 E

mrfEntries 150

Mean 77.97

RMS 37.46

Nch0 20 40 60 80 100 120

0.2

0.4

0.6

0.8

1

mrfEntries 150

Mean 77.97

RMS 37.46Best mrf(bottom) = 0.126009

Best cut at Nch=33 (bin 17)

Best Integrated Bgd = 4.79439

Int. Bgd (<bestcut) = 61.4359

Best Integrated Sig = 40.5372 ---------------------------------

mrf at cut = 0.129037 Cut Nch=46 (bin 24)

Best Integrated Bgd = 1.06569

Int. Bgd (<cut) = 60.625

Best Integrated Sig = 25.7652

Model Rejection Factor

IceCube 9 string ~ 137daysScale factor of test flux vs Nch cut threshold

Min. 0.13

Nchcut = 46

• Scale factor is very flat between Nchcut ~30 and 50

ChooseNchcut = 46

to get sensitivity

(GeV)]!

[E10

log3 4 5 6 7 8 9

]-1

sr

-1 s

-2 d

N/d

E [

Ge

V c

m2

E

-910

-810

-710

-610

-510

-410 data (prelim.)µ!AMANDA-II 2000 atms.

! + prompt atms. !Barr et al. atms.

! + prompt atms. !Honda et al. atms.

!Max uncertainty in atms.

Frejus

MACRO

diffuseµ!AMANDA B-10 1997

AMANDA-II 2000 Cascades (all-flavor / 3)*

AMANDA B-10 1997 UHE (all-flavor / 3)*

Baikal 1998 - 2002 ( all-flavor / 3 )*

RICE 1999-2005 ( all-flavor / 3 )*

AMANDA-II 2000 unfolding (prelim.)

AMANDA-II 2000-2002 UHE limit (prelim.)

limitµ!AMANDA-II 2000-3

W&B limit/2 (transparent sources)

Full IceCube 1 yr

* assumes a 1:1:1 flavor ratio at Earth

IceCube 9 strings 137days

Diffuse Muon Neutrino Sensitivity of IC9 137 days (2006)

AMANDA-II807days upper limit

E-2 < 1.3 x 10-7 GeV cm-2 s-1 sr-1

IC9 137days sensitivity is factor 2 above AMANDA-II 807daysin 2007 integrated IceCube exposure exceeds AMANDA-II 4yr

• AMANDA-II 807days upper limit on the diffuse flux of muon neutrino with a AconstE-2 spectrum for the energy range 16 TeV to 2.5PeV is

• Monte-Carlo verification for IceCube 9 string has done with Nch<46 low energy data. MC data shows reasonable agreement with the data sample.

• The sensitivity of IceCube 9 string 137days for the energy range from 40TeV to 20PeV is

which is factor 2 above AMANDA-II 807days.

E-2 < 7.4 x 10-8 GeV cm-2 s-1 sr-1

E-2 < 1.3 x 10-7 GeV cm-2 s-1 sr-1

Summary

Outlook IceCube-22 with AMANDA

-200

-100

0

100

200

300

400

500

600

0 100 200 300 400 500 600

xIceCube [m]

yIc

eC

ub

e [m

]

1

2

345

6 7

8

9 10

1112

13

14

15

16 17

18

19

21DL1

29

30

38 39

40SC1

49

50DL2

59

46

47 48

5657

BC

58

6566

rDL

67

7273

74

78

ice flow

Grid N

ort

h

Analyses for 22 string is now in preparation

Physics run of IceCube 22 started in 5/23

• Detector Volume : x 2~3 of IC9

• Accumulted Livetime :~3month by now

• Backup slides