Neutrino%20Astronomy%20in%20Ice

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Neutrino Astronomy in Ice

• Albrecht Karle
• University of Wisconsin - Madison
• NOW 2006

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Outline

• Introduction
• Neutrino astronomy motivation
• Antarctic ice as a detector medium
• Optical detectors AMANDA and IceCube
• Current results
• IceCube construction status
• Detectors for extreme energies New methods
• Conclusions

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Physics Motivation

• Search for cosmic-ray accelerators
• Protons are bent in galactic magnetic fields
• n are produced by hadron accelerators
• HE (gt51013 eV) photons are absorbed by
  interaction with 30K microwave background photons
• gg --gt ee-
• Study the High-Energy Universe
• 100 GeV 1019 eV
• Cross section effective area rise with energy,
  so a single detector can cover a very wide energy
  range

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Physics Topics

• Searches for cosmic accelerators
• Active Galactic Nuclei
• Supernova Remnants
• Gamma-Ray bursters
• Neutrino physics
• Cross-section measurements
• Via absorption in earth
• Oscillations
• Searches for supersymmetry, WIMPs, MeV n from
  supernovae, monopoles, .

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Active Galactic Nuclei and GRBs
Extragalactic sources are expected to produce up
to hundreds events/yr/km2
HESS J1303-63.1 Unid source 12 kpc 15000 yrs
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Messengers from the Universe

• Straight line propagation to point back to
  sources

• Small absorption in sources and during
  propagation

Cosmic accelerator
Photons absorbed on dust and radiation. For E gt
100 TeV do not survive the journey from the
Galactic Centre Neutrons decay
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Universe is not transparent for HE photons or
nuclei!
Figure by P. Gorham
g gCMB -gt e e- pgCMB -gt D-gtnp
mnm GZK -
neutrinos
Protons deflected by magnetic field for E lt 1019
eV! Not pointing back to the source! Need
neutrinos for high energy (gt10TeV) astronomy!
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Neutrino production bottom up
Beam-dump model p0 ? g-astronomy p ?
n-astronomy
Neglecting g absorption (uncertain) ?n ? ?g

Targets p or ambient g
At E gt 100 TeV
1 2 2
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Sources
Cosmic rays

• Candidate sources
• SN remnants, ?Quasars
• Active Galactic Nuclei
• Gamma Ray Bursts
• Dark Matter
• Exotics

T. Gaisser 2005
knee 1 part m-2 yr-1
Ankle 1 part km-2 yr-1
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Cosmic rays and neutrino fluxes
Waxman, 2006
Bound flux if CR lose Energy making pions This
is the case for GZK (guaranteed flux)
AMANDA II, 4 YR
CR lose energy Inside starburst
galaxies. Electrons (synchrotron) Provide
calibration Waxman, astro/ph 0601695 Has been
argued recently to be lower, eg Stecker
IceCube, 3 yr
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Neutrino and cosmic ray detectors in Antarctica

• In final configuration and operation
• SPASE II air shower array with 100
  scintillators at surface
• AMANDA-II 19 strings, 667 PMT, 1500 -2000m
• RICE
• In preparation, construction and/or preliminary
  operation
• IceCube Neutrino observatory, optical ice
  cherenkov, 80 strings, 5000PMT,
• ANITA Radio ice cherenkov, Balloon flight 06/07
• Experiments in proposal and/or prototyping phase
• AURA radio ice
• SPATS acoustic detection in ice
• ARIANNA, radio ice shelf

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NT operate at a wide energy range 100 GeV to
beyond 1 EeV
Neutrino telescopes operate over wide Energy range

• The negative power law spectra of cosmic
  accelerators is compensated by the increasing
  effective detection area
• Effective area for nm
• Why?
• Increase of muon range with energy
• Wide energy range unique to neutrino telescopes
  much smaller for cosmic ray or gamma ray
  detectors.
• Sensitivities for diffuse signals comparable for
  cascades.

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Antarctica is Huge Cold Dry Icy Empty
40 4400km
McMurdo
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Antarctic Ice

• Antarctic ice sheet
• Thickness up to more than 4 km
• Area gt North america
• Possible detection methods for neutrinos
• Optical detection (ice Cherenkov, (below 1400m)
• Absorption length_at_400nm gt100m
• Effective scattering length gt20m
• Extremely low noise (300pe/sec/PMT)
• Radio detection (ice Cherenkov, Askaryan)
• Estimated absorption length gt1 km
• Acoustic detection
• Estimated absorption length gt 1km
• Low noise

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• Physics Backgrounds
• At energies lt 1 PeV
• Atmospheric muons (downgoing)
• Atmospheric neutrinos (upgoing)
• Earth absorption effects
• At high energies gt 1 PeV
• Zenith angle dependent
• nt regeneration

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Some AMANDA results
Some results presented by the IceCube
collaboration at Neutrino 2006, Santa Fe

• Point sources
• GRB
• Diffuse flux limit

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Limits to diffuse fluxes
Hill, IceCube Coll. at Neutrino 2006)
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Point source analysis
Optimal search window
2000-2003 3329 events 807 days
live-time2000-2004 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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Northern hemisphere grid search
2000-2003
Significance / s
Significance / s
2000-2004
Largest fluctuation 3.7s at 12.6 h, 4.5
deg compatible with position of EGRET source 3EG
J12360457
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Northern hemisphere grid search
Random events
Significance / s
2000-2004
Significance / s
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Search for Neutrinos from GRBs

• Upper limit E2F? lt 310-8 GeV cm-2 s-1 sr-1
  (muon)
• Assumed average spectral shape from
  Waxman-Bahcall
• Aggregate limit including newer data about factor
  of 10 above Waxman-Bahcall prediction (Neutrino
  2006)

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Limits on point sources
Results
Point Source Search
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IceCube 2006
IceCube array 70 strings planned 9 strings and
540 DOMs installed IceTop array 70 locations
planned 16 locations and 64 DOMs installed
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2005, 2006, 2007 Deployments
AMANDA
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IceCube string and IceTop station deployed 01/05
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IceCube string and IceTop station deployed 12/05
01/06
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IceTop station only 2006
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IceCube string and IceTop station to be deployed
12/06 01/07
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604 DOMs deployed to date Next year looking for
12 strings. IceTop will be backed off to remain
in line with hole deployment Want to achieve
steady state of 14 strings / season.
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The Enhanced Hot Water Drill (EHWD) in 2006
Supply 200 GPM _at_ 1000 psi, 190 FReturn 192
GPM _at_ 33 F Make-Up 8 GPM _at_ 33 F
EHWD designed to drill a 2450 m 60 cm hole in
30 hr. Fuel budget is 7200 gal per hole. Shown
above is drill camp and tower site (inset), both
mobile field arrays. Everything must fit into
LC-130 for transport to Pole.
Thermal Power 4.5 MW
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Drilling strategy 06/07

• Maintenance, upgrades and tuning.
• Overall no fundamental changes to drill strategy
  and equipment.
• Larger crew of 30 people to sustain 3 shift
  schedule 24/7
• New firn drill strategy in 06/07

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String installation

• 10 hour deployments we successful.
• No changes in equipment.
• Higher integration in drill operation.

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String 39 two-week freeze-in movie
Mark Krasberg
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Fundamental detector elements
Digital Receiver (PCI card)
IT (TCP-IP)
20C
up to 3.3 km copper, 0.9mm (twisted pair, power,
data, time synchronization)
-40C
Intelligent Digitizer (DOM)
PMT
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DOM (Digital Optical Module) Power consumption
3.5 W Digitize at 300 Mhz, 400 ns 40 MHz,
6.4 µs Send all data to surface over copper Two
sensors/twisted pair. Flasherboard with 12
LEDs Local HV
Clock stability 10-10 0.1 nsec /
sec Synchronized to GPS time every 2 sec at a
precision of rms 2 nsec (design goal 5 nsec)
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Pulse shapestaken in situ

• Pulse shapes are recorded with three ATWD
  channels for high dynamic range coverage.
• Runs of 10 pulses at 5 different brightness
  settings are shown.
• High saturation in channel 0, but good coverage
  of the brightest pulses in channel 2.

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Low noise rates -higher sensitivity to Supernova
Importance of noise rates 1.) noise rate w/o
dead time 700 Hz, important for DAQ
bandwidth 2.) noise rate w/suppression of 50µs
300Hz, important for event reconstruction and in
particular for supernova sensitivity. Two
Icecube strings probably more sensitive than all
of AMANDA.
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The Timing system works
Flasher tests are used to verify the timining
system. The figurefrom string 21 (2005) shows
rms spread of 2 neighboring DOMs from flasher
pulses. The timing system works also on all new
strings and IceTop stations in 2006.

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Occupancy data

• The number of recorded hits on the strings is
  plotted versus the depth.
• Indication for overall uniformity of strings.
  (need to wait until all are at same temperature)
• Features indicate changes in triggered muon flux
  and optical structure of the ice.

Z position m
Triggered events for strings with 8 or more hits
, normalized.
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Cosmic ray muons Data and Monte-Carlo coming
together

• Event rates
• Trigger 8 fold (gate 5 µsec LC, 1µsec)
• Cosmic ray muons 140 Hz (MC 180Hz).
• Atmospheric n simulation 0.0004Hz (35/d)

The azimuthal structure reflects the geometry of
the 9 strings. Simulations reproduce the detector
response.
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Neutrino event
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Event Signatures in IceCube
Neutrino Telescopes
IceCube
1013 eV (10 TeV)
6x1015 eV (6 PeV)
Multi-PeV
??
B10
??N??...
? (300 m!)
?? ??hadrons
signature of ??
signature of ??
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IceCube with IceTop surface array
Area--solid-angle 1/3 km2sr (including angular
dependence of EAS trigger)

• Calibration
• Veto of HE shower background
• Cosmic Ray/air shower physics up to 1018 eV

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IceTop tank
Each 2 m diameter IceTop tank contains two DOMs.
Yes, this is ice, not water!
m signals from IceTop DOMs
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High energy cosmic ray air shower event
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Primary composition with IceCube

• Nm from deep IceCube Ne from IceTop
• High altitude allows good energy resolution
• Good mass separation from Nm/Ne
• 1/3 km2 sr (2000 x SPASE-AMANDA)
• Covers sub-PeV to EeV energies
• Very good energy resolution possible.
  SPASE-AMANDA Mass independent energy resolution
  of air shower primary for 1ltE/PeVlt10
• ????????????????sE 0.07 log(E)

Figure by Ralph Engel
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SPASE - AMANDA Energy resolution of air shower
primary
Energy resolution of air shower primary for
1ltE/PeVlt10 ????????????????sE 7 log(E) (Mass
independent based on MC)
Proton
Iron
5 6 7 8
Log(E_true/GeV)
5 6 7 8
Log(E_reconstructed/GeV)
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Limits on point sources
Results
Point Source Search
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IceCube EHE Event Channels

• Possible EHE particles in depth

Fluxes at the IceCube depth
Atm m
n
EGZK gtgt EAtmm
n
t
m
Secondary m and t
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Coherent Radio signalfrom electromagnetic cascade
charge asymmetry in particle shower development-
combined effects of positron annihilation and
Compton scattering on atomic electrons result in
a 20 excess of electrons over positrons in a
particle shower
wavelengths shorter than the bunch length suffer
from destructive interference
moves as a compact bunch, a few cm wide and 1cm
thick
electric field strength proportional to the
square of the shower energy
Gurgen Askaryan (1928-1997)
is the length of the bunch
Add coherently!
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Why Ice? Why Radio?

• Long attenuation - Radio 1km
• Optical attenuation in ice 100m
• No scattering for Radio In ice.
• A lot of it.
• Free to use.
• South pole is isolated. RF quiet.
• Antennas are cheaper and more robust than PMTs.
• No need to drill wide holes
• lower drilling cost of deployment w.r.t optical
  detectors
• 1016 - 1023 eV

1017
Effective volume per detector element for ne
induced cascades
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RICE
Radio Ice Cherenkov experiment

• Made surveys of rf properties of the ice at the
  South Pole
• Set most stringent limits on the neutrino flux
  from 1016 to 1018 GeV
• Utilized the infrastructure and deployment of
  AMANDA

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AURA
The Askaryan UnderIce Radio Array
Endorsement by IceCube.

• Develop technology for larger radio array
• Further map out the radio properties of South
  Pole Ice
• Build intermediate detector with improved
  effective volume over RICE

• LABRADOR chip developed for ANITA has gt1GHz
  bandwidth, low power consumption, small deadtime,
  and has been tested to low temperatures.
• IceCube holes, cables and DAQ design including
  DOM Mainboard power and time stamping.
• Use pressure vessel, add connectors for antennas.
• Use RICE experience with antennas.

KU
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Digital Radio Module
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(No Transcript)
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ANITA collaboration prepares flight
Slide from Gary Varner, presented at TeVII
workshop, Sep 06
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Acoustic detection

• Detect the acoustic sound wave generated by the
  expansion caused by the heat dissipated in the
  shower. Energy threshold gt1e17 or 1e18eV
• R D
• World wide activities. Ice expected to be
  significantly quieter than water (no waves, rain
  and dolphins).
• Initial Goal determine acoustic properties of
  ice
• Absorption length
• Noise levels
• Three test strings ready for deployment in 05/06
  season. Deployment was not approved by NSF for
  logistics support reasons.
• Hope/expect this year deployment.

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Acoustic sensors completed in 2005
Endorsement by IceCube
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Other ideas/proposals
Radio from gteo synchrotron radiation of Air
showers LOFAR/LOPES Threshold100 PeV, LOPES
must be externally triggered by ground
detectors. 5 highly inclined events in 2004 data
ARIANNA on Ross iceshelf?
Possible extension of IceTop?
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Possible scenarioof a GZK scale detector
300 microphones/string
5 antennas/string
Observation of UHE neutrinos by more than one
method could make for a more compelling discovery
claim
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Conclusions

• Antarctic ice is a unique medium for high energy
  particle astrophysics.
• AMANDA continues to deliver results.
• IceCube now in full construction. 9 strings
  operational, taking data at 150 evts/sec, 12 to
  be added by January 06.
• First IceCube data consistent with expectations.
  DOM performance meets or exceeds expectations.
• String deployment plan 12 strings next year
  (logistics support for 14), then 14 each year
  thereafter. Looking to reach target of 75
  strings.
• Discovery potential growing.
• Ice is very promising target medium for radio and
  possibly acoustic detection of highest energy
  neutrinos (EeV).
• Hybrid detectors may reduce systematics at
  highest energies (no atmospheric neutrinos as
  reference signal).

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IceCube effective area and angular resolution for
muons
further improvement expected using waveform info
Median angular reconstruction uncertainty 0.8?

• E-2 nm spectrum
• quality cuts and background suppression (atm m
  reduction by 106)