IceCube Physics, Design, Construction and First Results

1
IceCube - Physics, Design,Construction and
First Results
Spencer Klein, LBNL

• Cosmic-rays and Neutrinos
• Neutrino Sources and Rates
• IceCube
• Conclusions

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

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

USA (13)
Japan
Europe (13)

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

New Zealand

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

ANTARCTICA

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

3
then
Mysterious radiation from space
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An Air Shower in the Pierre Auger Observatory
and now
Co
Radius (m)
3.6 m
SLAC to scale)
5
Cosmic Rays An Unsolved Problem

• 13 decades in energy
• Seen up to 31020 eV
• 48 Watt-sec
• Above 10161 eV, origin and composition are
  mysteries
• Extra-galactic?
• Many, many theory papers

108 eV
1021 eV
6
Cosmic Rays in the Galaxy

• Galactic Sources
• Supernova remnant accelerators may reach 10161
  eV
• Supernova produce a large nuclear component
• Leaky Box Model
• High energy CR diffuse out of galaxy
• At fixed energy, nuclei are confined better than
  protons
• ltAgt increases with energy
• By default, higher energy CR are extra-galactic
• Mostly protons?

106
108
E (GeV)
7
Composition
Iron

• Satellites or balloons data lt 1015 eV
• Energy reach limited by detector size
• Indirect Determination is difficult
• Ground based detectors
• Leakage through a 30L calorimeter
• Shower shape, m content
• Fluorescence Arrays
• Depth of Shower Maximum
• Sensitive to hadronic interaction models
• Composition varies with energy
• Ion fraction increases up to 1015 eV, may
  decrease above 1018 eV

Proton
AMANDA ( of m)
log(E/PeV)
Spase ( of e)
Flys Eye
Depth of Xmax (g/cm2)
Log E (EeV)
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Cosmic Ray Propagation in the Galaxy

• Ions bend in the Galaxy's magnetic field
• Q B/ZE
• Below 1019 eV, cosmic rays do not point to their
  source
• At higher energies, it depends on the simulation
  parameters, especially the assumed B field
• Most studies of EHE cosmic rays find no
  clustering

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Cosmic Ray Interactions

• p g3K --gt D --gt np
• CR range lt 50 megaparsecs _at_ 1020 eV
• GZK cutoff
• Egt1020 eV sources must be near
• Cutoff present in HiRes data
• Not seen by AGASA
• Auger seems to support HiRes
• p? decay guaranteed source of EHE neutrinos
• Also p g3oK,IR starlight --gt pee-
• Heavier ions are destroyed by photodisintegration
• Similar (or worse) range limits

Absorption 1/E dE/dt (ly-1)
Log10(Energy)
Michael Kachelrieß, 2004
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Source Characteristics

• Passage through a shock wave can accelerate
  charged particles via Fermi Acceleration
• Fractional energy gain per passage z lt 1
• Circular accelerator
• Typical time scale 250 passes 1,000 years
• Magnetic confinement allows repeated passes
• Emax (eV) 2 104 B(Gauss)L(m) (Z)
• Relativistic jets can have similar accelerating
  qualities in a single pass
• Power law spectrum dN/dE 1/E2
• Predicted by many studies, models

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Some Possible Sources
Michael Kachelrieß, 2004
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Supernovae Remnants

• Neutron star in the center powers system
• B field, gravitation, accretion
• Photons observed from Crab nebula with E 10 TeV
• Consistent with synchrotron radiation inverse
  Compton scattering
• Magnetic field matter/shock front distribution
  allow acceleration to 1015-17eV/A
• Popular galactic source
• Lots of nuclei present

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Active Galactic Nuclei

• Galaxy with a supermassive black hole at center
• Emits a narrow jet of relativistic particles
• Jet-matter interactions produce n g
• Markarian 501 seen from radio waves to 10 TeV
• Spectrum indicates probably not electromagnetic
  acceleration
• Similar spectra seen from galactic center

VLA image of Cygnus A
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Direct Production?

• Decays of superheavy particles produce high
  energy protons, photons and n
• Magnetic monopoles
• X particles
• topological defects
• etc.
• Annihilation of heavy/superheavy big-bang relics

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Neutrinos probe CR sources

• Photons are absorbed by matter at the source and
  interact with cosmic microwave photons in transit
• Charged cosmic ray are bent in transit
• n come straight to us
• Cross sections are small
• A large detector is needed

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Neutrino Production

• Cosmic-ray acceleration occurs in low-density
  matter
• beam-gas interactions
• Produced p and K decay before they can interact
• p ? ,K ? --gt mnm, m--gt enenm
• n vs n-bar difference c, b --gt lnX often
  neglected
• Two approaches to calculate n flux
• Source density known CR spectrum set number of
  n-producing interactions
• n come from ions that dont escape the source
  could be more numerous than those that do
• Maximum n energy is a few of ion energy
• Assume photon production from p0--gtgg
• N(p0 ) N(p ) p decay chain emits n
• Avoids uncertainty due to CR composition

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Cosmic Ray Composition n Flux

• Ion acceleration as protons, but Emax is Z times
  higher
• Ions dissociate into lighter ions, p, n, etc.
  when they interact
• Toy model nucleus A --gt A excited nucleons
• A times as many n, but with energy E/A
• Large reduction in HE n flux
• Nuclear b decay also contributes

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n production in AGNs
Frejus Limit

• Scale TeV photon data to estimate n spectra
• Estimate g absorption
• n attenuation in earth
• Assume g come from p0
• Total of 1,000 upward nm/year from all AGNs
• with En gt 1 TeV
• Diffuse Flux
• Are individual AGNs visible?

Flux
En (GeV)
R. Gandhi, C. Quigg, M Reno and I. Sarcevic, 1996
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production in gamma-ray bursters

• Burst of gs with energies up to at least 10 GeV
• Durations from seconds to minutes
• Allows nearly background-free searches
• Colliding compact objects (e.g. neutron
  stars/black holes)
• Short duration (lt2 s)
• hypernova collapse of a supermassive star
• Long duration (gt2 s)
• Theory predicts g and n emission up to very high
  energies
• Estimate rate on a burst-by-burst basis using
  measured burst characteristics
• Best search sensitivity by focusing on biggest
  bursts
• IceCube should see 1-2 n from the these bursts

GRB000131
(modulo some recently seen bursts)
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Measuring snN by neutrino absorption in the earth

• The earth becomes opaque to neutrinos with
  energies gt 200 TeV
• n Angular distributions are known
• Measure cross section by studying n flux as
  f(zenith angle, energy)
• Usable up to En few PeV
• Maximum energy depends on poorly known n flux
  on detector acceptance near horizon
• Absorption snN
• Sensitive to weak charge (quarks) to
  x few 10-4

Absorber thickness Depends on zenith angle
fraction
xmin
J. Jalilian-Marian, 2004
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Strategies for Extra-terrestrial Neutrino
Searches

• nm Point Sources
• Diffuse Searches
• Most sensitive if there are many sources
• p,K decay produces nm, ne 21
• Oscillations change this to 111 nenmnt for
  distant sources
• Muon energy loss alters ratio at high energy
• ne
• Good energy resolution, poor angular resolution
• nm
• Good angular resolution, poor energy resolution
• Atmospheric neutrino background
• nt
• Very low background
• Triggered (e.g. GRB) untriggered burst searches

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nm interactions

• Good directional information
• Background from atmospheric n
• m lose energy by bremsstrahlung, direct pair
  production photonuclear interactions
• dE/dx E for Egt 1 TeV
• Range depends on energy
• 1 TeV --gt 1 km in ice
• 1 PeV --gt 20 km range
• Effective area is much larger than detector volume

Eµ10 TeV, 90 hits
Measure range /or dE/dx to get energy
Eµ6 PeV, 1000 hits
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ne interactions Electromagnetic Showers

• Shower length 10 m --gt good energy resolution
• Bloblike --gt poor directional determination
• Peak in cross section for ne gtW --gt ln,
  hadrons
• Glashow Resonance
• Techniques are much less developed than for nm

Gandhi, Quigg, Reno Sarcevic, 1996
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nt interactions

• ntN --gt tX
• gbct 500 m at E1016 eV
• Double-bang signature
• 1 shower when the t is produced
• 2nd shower when the t decays
• A minimum ionizing track connects the showers

Learned and Pakvasa, 1994
Et few PeV
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AMANDA Point source analysis
Optimal search window
2000-2004 4282 events 1001 days live-time

• Search for an excess of events
• from candidate sources
• anywhere on the northern sky
• Atm-n Background from off-source data
• No detection yet, flux upper limits set

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Atmospheric Neutrinos Diffuse nm searches

• Air showers produce n via p,K decays
• Mostly nm
• p,K Decay probability decreases with energy as
  gbct rises
• dNn/dE E-3.7
• Steeper than extra-terrestrial sources
  (typically E-2)
• High energies better for extra-terrestrial
  searches
• AMANDA set limits on E-2 spectrum
• E2??µ(E) lt 2.6107 GeV/ cm2 s sr
• For 100 TeV lt E lt 300 TeV

E-2 Limit
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Other Physics

• Supernova monitor
• Count total photoelectrons in all PMTs
• Dark Matter
• n from weakly interacting massive particles
  annihilation in the center of the earth or the
  sun
• Supersymmetry
• Pairs of upward going charged sparticles
• Separation 100 m
• Fast magnetic monopoles other exotica

Sol
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Detector Basics

• Need 1 km3 detector to see extraterrestrial
  signals
• Only natural media are affordable
• Cherenkov radiation from charged particles
• Sparse sampling optical detectors
• Water
• Homogenous ()
• Long scattering Length ()
• Relatively short absorption length (-)
• 40K bioluminescence background in seawater (-)
• Ocean currents (-)
• Pursued by DUMAND (1980s), BAIKAL, NESTOR,
  ANTARES NEMO
• European Km3 initiative in Mediterranean

NESTOR
ANTARES
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Ice Detectors

• Pioneered by AMANDA (1992)
• Observed atmospheric nm
• Learned many lessons
• Ice is inhomogenous
• Air bubbles _at_ lt 1,000 m deep
• Dust layers cause scattering
• Ice has a long absorption length
• But scattering is significant
• Cold Dark --gt Low Noise rates (lt 1 kHz)
• Transmission to surface nontrivial

A m in AMANDA
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IceCube

• 1 km3 neutrino observatory
• 4800 optical modules
• 10 phototube in a 13 sphere
• 80 strings with 60 modules
• 125 m hexagonal grid
• 1400 to 2400 m deep
• 160 station - 1 km2 surface array
• 242M NSF Major Research Equipment initiative
• 25M foreign contributions
• Transportation to the pole is expensive!

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IceCube
Skiway
IceCube
South Pole Station
2005/6Drill Site
Counting House
AMANDA
South Pole
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IceCube drill camp
5 MW hot water heater (car-wash technology)
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Hose reel
5 Megawatt Hot water generator
IceTop tanks
Hot-water drilling
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Hole Drilling

• 2500 m deep, 60 cm dia. holes
• 5 Megawatt hot water drill
• Mostly reliable operation
• Single heater, hose, two towers
• Set up one, drill with the other
• Speeds to 2.2 m/minute
• 40 hours to drill a hole
• 2004/5 1 string
• 2005/6 8 strings
• 2006/7 13 strings

AMANDA
IceCube
Depth vs. Time
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Deployment

• Attach DOMs to cable, lower away
• 12 hours/string
• Special Devices (1/string each)
• Dust Logger
• Standard Candle N2 laser
• BubbleCam
• Acoustic/Radio tests

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Dust Logger

• Measures Ice Optical properties
• Emits light perpendicular to hole
• Measures light scattered by dust
• Dust is due to volcanoes (narrow lines) weather
  over last 200,000 years
• Are the dust layers constant horizontal across
  IceCube?

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IceTop Surface Array

• 160 Detectors in 1 km2
• Energy to 1019 eV
• Ice filled tanks
• Cosmic Ray Composition
• Surface particles subsurface m
• High pT muons in CR air showers
• pQCD based composition studies
• Calibrate IceCube
• Veto downgoing cosmic rays
• g detector (w/ IceCube as a veto)

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IceTop

• Detects e, g from air showers
• 320 TeV threshold
• 2 water tanks near each string
• 1.8 m diameter
• Controlled freeze to minimize bubbles
• 2 DOMs

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2 IceTop Tanks ( 1 station)
m signals from IceTop DOMs
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Optical Modules

• Each optical module collects data autonomously
• 10 Photomultiplier w/ HV
• 300 MHz waveform digitizer
• Custom analog chip
• 40 MHz fast ADC
• Self triggering
• 1/4 photoelectron threshold
• lt5 Watts of power
• 700 Hz Dark rate
• 350 Hz w/ 51 ms deadtime
• LEDs for calibration
• Packetized Digital data sent to surface

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Digital Optical Module Mainboard
300kgate FPGA w/ ARM 7 CPU
Crystal oscillator Allen Variance lt 510-11
Custom Switched Capacitor Array 128 sample 300
MSPS 2/board
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Data Acquisition

• Goal Detect every photoelectron
• Record waveforms from non-isolated hits
• 400 nsec _at_ 300 MSPS
• 14 bit dynamic range
• 3 10-bit channels
• 6.4 msec _at_ 25 MSPS
• 10 bit dynamic range
• Time Stamp isolated hits
• Trigger on multiplicity, topology
• Frame (Event) All hits in a given time window
• Commercial electronics on surface

ATWD1
ATWD0
fADC
ATWD2
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Reconstruction Performance

• Timing Calibrations
• Reconstruction Methods
• Neutrino Events
• Atmospheric neutrino analysis

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Time Calibration
Time
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Optical properties of the ice
Scattering
Absorption
bubbles
ice
dust
dust
Measurements in-situ light sources atmospheric
muons Dust Logger
optical WATER parameters labs 50 m _at_ 400
nm lsca 200 m _at_ 400 nm
Average optical ice parameters labs 110 m _at_
400 nm lsca 20 m _at_ 400 nm
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Particle (m) Tracking

• m tracks lose energy by emitting g, ee- pairs
  and hadronic interactions (via virtual g)
• Charged particles emit Cherenkov radiation
• angle q Cos-1(1/n) 410
• The photons scatter (L 25 m)
• Some (lt10-6) photons are observed in
  photodetectors
• We measure points 0-50 meters from the m track
• Tracking is very hard we do not have the
  optimal solution
• Angular resolution lt 10

m
Noise
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Neutrinos Observed
Time residuals from fit Direct scatted photons
A 2005 Neutrino candidate 49 DOMs hit in String
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2006 Neutrino candidate 24 DOMs hit in 2 strings
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A high-multiplicity event
Time residuals vs. depth
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Atmospheric Neutrinos

• 90 days of data with 9 strings
• Starting June 3, 2006
• 156 events observed
• 144 12 48 events expected
• 138 atmospheric nm
• 4.4 single cosmic-ray m
• 2.3 overlapping cosmic-ray m
• 2 independent showers at the same time
• n rate will increase with larger detector,
  slightly more efficient data taking and optimized
  tracking selection criteria
• Expect 100,000 atmospheric n/year with full
  detector

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Multi-parameter measurementwith IceCube/IceTop
Cosmic Ray

• IceTop measures air shower energy, direction
  core position
• InIce measures
• Muon energy, by dE/dx
• Muon bundles near shower core
• Muon pT, by distance from core
• (away from core region)
• pT Emcore_distance/production_height
• Perform standard (collider-like) pQCD studies
• Sensitive to cosmic-ray composition

N2
25 km
e,g
m From c,b
m from p,K
S. Klein, astro-ph/0612051
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Logistics home base
The New
The Old
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Getting there is half the fun
Logistics Transportation
New C-17
Old C-141
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Logistics Transportation
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Conclusions

• UHE Cosmic Rays are one of the great unsolved
  problems in physics
• Direct source searches are hampered by
  interstellar magnetic fields
• Studies of extraterrestrial n will shed light on
  the origin and composition of UHE cosmic rays.
• IceCube construction is well underway.
• We have deployed 22 out of 70-80 strings.
• Construction is scheduled for completion in 2011.
• The hardware is working well.
• We have seen our first neutrinos
• First physics results are coming out.

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Backups, etc.
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DOM Occupancyprobability a DOM is hit in events
that have gt7 hits on a string

• Features in DOM
• occupancy are
• affected by ice
• properties
• (scattering,
• absorption)

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Timing Stability
Long tail from scattered light

• Select muon tracks that pass near target DOM
• Nearby --gt unscattered light
• Find mean of residual
• Compare data from June, 2005 Sept. 2005

Dusty Ice
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How many sources?Do cosmic rays cluster?
E gt 1020 eV 4 1019 eV lt E lt 1020 eV
Multiplets

• No obvious connection between cosmic rays and
  interesting directions.
• Clustering?
• Most analyses indicate no

60
Neutrino Production fromNuclear propagation

• For ions, photodissociation replaces D production
• Breaks nucleus up into lighter ions, protons,
  neutrons.
• Neutrons and fragments can b decay
• ne, but with quite low energies
• Since sn En, signal drops quickly as A rises
• Very little signal for Agt4

b decay
m decay
Hydrogen Helium Oxygen Iron
Hooper, Taylor and Sarkar, 2004
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WIMP searches
Disfavored by direct search (CDMS II)
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Search for steady point sources
Search cone 1? opening half-angle soft energy
cut (lt 1 TeV)
Sensitivity point sources (1 y) 5.5?10-9 E-2
(cm-2s-1GeV)
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Angres
Angular resolution as a function of zenith angle
Waveform information not used. Will
improve resolution for high energies !
0.8 0.6

• above 1 TeV, resolution 0.6 - 0.8 degrees for
  most zenith angles

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Supernova Monitor
Amanda-II
AMANDA II 95 of Galaxy IceCube Milky Way
LMC msec time resolution
You are here
LMC
IceCube
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Effective Area of IceCube
Effective area vs. zenith angle after rejection
of background from downgoing atmospheric muons

• Effective area vs. muon energy
• - after trigger
• - after rejection of atm ?
• after cuts to get the ultimate
• sensitivity for point sources
• (optimized for 2 benchmark spectra)

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Transient point sources e.g. GRB
Essentially background-free search spatial and
temporal correlation with independent
observation !

• For 1000 GRBs observed/year
• expect (looking in Northern sky only)
• signal 12 ? (Waxmann/Bahcall model)
• background (atm ) 0.1 ?

Sensitivity GRB (1 y) 0.2 ?WB
Excellent prospects for detection of GRB ?s
within 1 year (if WB model realistic)
t01h
Waxman/Bahcall 99
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Search for diffuse excess of extra-terrestrial
high energy neutrinos
log E? /GeV
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IceTop surface array

• 160 Detectors in 1 km2
• Energy to 1019 ev
• Tank of ice with 2 OMs frozen in them
• Cosmic Ray Composition
• Surface particles subsurface m
• High pT muons in CR air showers
• pQCD based composition studies
• Calibrate IceCube
• Veto downgoing cosmic rays
• g detector (w/ IceCube as a veto)

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Neutrino Production frompropagating protons

• Guaranteed (albeit small) source
• p g (30K) --gt D --gt np
• p --gt mnm, m--gt enenm
• En/Einitial p 1
• Few events/year
• 0.2/km3 target volume /year
• Engel, Seckel and Stanev, 2001
• 2/km3 target volume/year
• Hooper, Taylor and Sarkar, 2004
• GZK neutrinos