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IceCube: A Neutrino Telescope at The South Pole

Chihwa Song

UW-Madison

photographed by Mark Krasberg

4th Korean Astrophysics Workshop May 17-19, 2006

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Multi-messenger Astronomy Radio

Infrared

Optical

Gamma Ray

deflected

absorbed

pee p + + n

+radio

+IRe+e-

+MW

Local Group

3C279

Mrk421

Gal Center <100 Mpc 1-10<100 Mpc 1-1099 TeV TeV

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Neutrino Fluxes Confirmed extraterrestrial sources: Sun, SN1987A

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Cosmic Accelerators

Discovery of neutrinos would confirm hadronic acceleration

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Origin of Astrophysical Neutrinos

Source candidates: AGN, SNR, GRB, microquasar

Protons accelerated at source produce pions which decay into neutrinos:

e = 1 : 2 : 0

p + p (or e

e = 1 : 1 : 1

p DX

p X

10 3

@ source

@ Earth

oscillation(maximal mixing)

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Neutrino Telescopes

Detection Requirements: - small neutrino cross section huge detector volume

- optically transparent medium use water or ice

Neutrino telescopes: - Water: Baikal, ANTARES, NESTOR, NEMO, KM3 - Ice: AMANDA, IceCube (successor of AMANDA)

Water Ice

Location Northern Southern

Deployment weather allowed austral summer

Background high low

Scattering length ~100 m ~20 m @ 400nm

Attenuation length 20-40 m ~110 m @ 400 nm

Detector geometry variable stable

Neutrino Detection Detect Cherenkov light from charged particles produced by neutrinos

: CC e : NC, CC

: NC, CC: NC

CascadeMuon track

CC NC

= 41o

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E = 10 TeV

e

E = 375 TeV

Neutrino Flavor

E = 10 PeV

travel ~2km

Two showers separated by roughly 50(E/PeV) m

80 string IceCube

~300m0.65o (E/TeV)-0.48

(3TeV < E< 100TeV)

Background

Zenith angle

• Miss-reconstructed down-going events• Up-going atmospheric neutrino events

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Signal: harder spectrum (E-2) than background (Fermi acceleration)

E-3.7 atmospheric

E-2 flux

True neutrino energy Number of fired OMs

Diffuse Neutrinosfrom unidentified faint sources

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USA (14)

Europe (15)Japan

New Zealand

• Alabama University, USA• Bartol Research Institute, Delaware, USA• Pennsylvania State University, USA• UC Berkeley, USA• UC Irvine, USA• Clark-Atlanta University, USA• University of Alaska, Anchorage, USA• Univ. of Maryland, USA

• IAS, Princeton, USA• University of Wisconsin-Madison, USA• University of Wisconsin-River Falls, USA• LBNL, Berkeley, USA• University of Kansas, USA• Southern University and A&M College, Baton Rouge, USA

• Universite Libre de Bruxelles, Belgium• Vrije Universiteit Brussel, Belgium• Université de Mons-Hainaut, Belgium• Universiteit Gent, Belgium• Humboldt Universität, Germany• Universität Mainz, Germany• DESY Zeuthen, Germany• Universität Dortmund, Germany

• Universität Wuppertal, Germany• MPI Heidelberg, Germany • Uppsala university, Sweden• Stockholm university, Sweden• Imperial College, London, UK• Oxford university, UK• Utrecht university, Netherlands

• Chiba university, Japan• University of Canterbury, Christchurch, NZ

ANTARCTICA

The IceCube Collaboration

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IceCube

InIce80 strings60 OMs / string17 m vertical spacing125 m between strings

IceTop80 stations2 frozen-water tanks / station2 OMs / tank

Super Kamiokande

40m

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main board

LED flasher board

PMT base

PMT

33 cm Benthosphere

Digital Optical Module (DOM)

Hamamatsu R7081-02 (10”, 10-stage, 108 gain)

- Time-stamp at the PMT- Capture complex waveforms at PMT anode with analog Transient Waveform Digitizer (ATWD)

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Hot Water Drill

speed: 1.5m/min

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Drilling

String 49 – drill stopped for ~one hour at ~2300 meters

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Freezing IceNoise rates increase during freeze-in String freezes from top (colder ice) to bottom (warmer ice)

Top

Botto

m

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Dust Logger

ash layer

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Ice Properties

Scattering

bubbles

Absorption

Average optical parameters:abs ~ 110 m @ 400 nmsca ~ 20 m @ 400 nm

dust layer

DOM occupancy at string 21

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Two ice tanks 3.6 m2 x 1 m deep

IceTop Station

To DAQ

IceCubeDrill Hole

10-15 m

Local coincidence cable

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04/05 1 IceCube string8 IceTop tanks

05/06 8 IceCube strings24 IceTop tanks

Deployment Status

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An Up-going Event

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Data/MC Comparison

Event reconstructionwith only one string

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Down-going Muon Events

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A Flasher Event

Color: arrival timeSize: amplitude

6 vertical (top) LEDs

6 horizontal (bottom) LEDs

(Single LED run)

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Diffuse Neutrinos

No significant excesswas seen with AMANDA!

by Jessica Hodges

Astrophysical and prompt neutrino models

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Bursts of low-energy (MeV) neutrinos from core collapse supernovae

The produced positron is emitted almost isotropically

- AMANDA sees 90% of the galaxy- IceCube will see out to the LMC (Large Magellanic Cloud, ~50 kpc)

SN Neutrino Search

detection

radius

AMANDA

IceCube30 kpc

0 5 10 sec

Count ratesSimulation(IceCube)

O(10cm) long tracks

SNEWS (SuperNova Early Warning System) is a collaborative effort among Super-K, SNO, LVD, KamLAND, AMANDA, BooNE and gravitational wave experiments

Rate increaseon top of dark

noise

e+ p n + e+

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The Sun sinks maximally 23o below the horizon at the south pole

Horizontal events are very important!!

qql+l-

W+W-

ZoZo

Higgs…

Indirect search

Velocity distribution

Cosmic Rays:

WIMP Annihilation in the Sun

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New Method - Radio

– One cluster (4 antennas) in the next season– Increase to 2 clusters in the following seasons

~50m

Motivation: difficulties to cover very large detector volume with optical sensors

ROCSTAR (Retrofitted OptiCal SysTem Adapted for Radio)

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New Method - AcousticCalibration method in water has been developedIn-situ calibration in ice is needed

SPATS (South Pole Acoustic Test Setup)

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Summary

• IceCube will be a powerful all-flavor neutrino detector

• Significant improvement in angular and energy resolutions

• IceTop will measure cosmic rays up to ~ EeV with high resolution

• AMANDA will overlap the lower energy tail of IceCube sensitivity

• AMANDA has taken data for the 7th year

• String deployment speed reached expectation

• DOM survival rate is very good (~99%)

• Verifications of the new IceCube strings in progress

• The current IceCube is larger than AMANDA and provides science quality data

• On-going activities (radio, acoustic) toward ~100km3 detector

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Time DelayTime delay in arrival times of photons due to scattering in icedepends on the distance with respect to the muon track.

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Glacial Ice Flow

Rigid downto 2000 m

Stuck atbedrock

Lagging behind

Modeling from temperature profile

Flow direction

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A Neutrino Candidate Event

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Point Source Search

Final sample (4 yrs): 3369

0.214.502SS433

1.255.3610Crab Nebula

0.405.214Cygnus X-1

0.775.046Cygnus X-3

0.383.7151ES1959+650

0.685.586Markarian 421

Flux Upper Limit 90%(E>10 GeV)

[10-8cm-2s-1]

Expectedbackgr.

(4 years)

Nr. of events

(4 years)

Source

Search for excesses of events compared to the background from: 1. the full Northen sky 2. a set of selected candidate sources

•64% chance occurrence

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Search for Clusters in Northern Sky

• 2000-2003 data: 807 days livetime• 3329 neutrino events observed• Cluster search radius between 2.25o – 3.75o w.r.t. • Largest significance = 3.4 (92% chance occurrence)• No significant excess observed

Significance map

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Search For WIMPs

Limits on muon flux from Earth center Limits on muon flux from Sun

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Surprises?

Telescope User date Intended Use Actual use

Optical Galileo 1608 Navigation Moons of Jupiter

Optical Hubble 1929 Nebulae Expanding Universe

Radio Jansky 1932 Noise Radio galaxies

Micro-wave Penzias, Wilson

1965 Radio-galaxies, noise 3K cosmic

background

X-ray Giacconi … 1965 Sun, moon neutron stars

accreting binaries

Radio Hewish,

Bell 1967 Ionosphere Pulsars

-rays military 1960? Thermonuclear

explosions Gamma ray

bursts

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Sensitivities & Limits

ave

rag

e fl

ux

up

per

lim

it [

cm-2s-1

]sin

AMANDA-B10

AMANDA-II

IceCube 1/2 year

*

all-flavor limits

νμ (A-II 4yr)

νe+νμ+ντ (cascades A-II 1yr)

νe+νμ+ντ (UHE B10 1yr)

νe (cascades B10 1yr)

νμ (B10 1yr)

νμ (A-II 1yr)

νe+νμ+ντ (UHE A-II 1yr)

Icecube (1yr)

WB bound

LimitSensitivity

Diffuse search (E-2 flux hypothesis) Steady point source sensitivity