Searches for Dark Matter and Neutrino Oscillations with IceCube

1
Searches for Dark Matter and Neutrino
Oscillations with IceCube

• Carsten Rott
• Pennsylvania State University
• CCAPP Ohio State University
• Columbus, Ohio
• March 25, 2008

2
Overview

• Neutrino Astroparticle Physics
• IceCube Neutrino Observatory
• Recent Results
• Dark Matter
• Neutrino Oscillations
• Extensions and Outlook

3
Cosmic Neutrino Sources
p (p or ?) ? ?0 ? ? ? ? ? ?
?e?? ? ?e????
(120) (111)

• Protons interact in target and produce pions
• Neutral pions ? photons
• Charged pions ? neutrinos
• Oscillations result in 111 flavor ratio at
  detector

• Sources
• Active Galactic Nuclei
• Supernova Remnants
• Gamma Ray Bursts

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Astronomical Messengers

• Protons
• bent below 10 EeV
• above 50EeV GZK cut-off
• Photons
• scattered/absorbed above 50 TeV
• Neutrinos
• Unobscured view
• Point back to their sources
• Cover entire energy spectrum

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Active Galactic Nucleias cosmic accelerators
Auger Collaboration 20 of 27 events with E gt
57 EeV are within 3.1 degrees of an AGN less
than 75 Mpc away. Centaurus-A (4 Mpc, white dot)
is especially prominent. ( 57 EeV 0.01 Joule )
( 1 Mpc 3 million light years )

• AGN are cosmic accelerators
• Accelerated protons may (or may not)
• interact in or near the sources
• to produce neutrinos
• We want to find out by looking
• for neutrinos from AGN

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A Generic Optical Neutrino Telescope

• Neutrinos interact in or near
• the detector
• O (km) muons from ?µ
• O (10m) cascades from ?e, ?t, NC

l, ?l
?l
W, Z
Cherenkov radiation
hadronic shower
Muon
Muon Neutrino

• Optical modules record
• absolute time with high precision
• intensity of light (photon counting)

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Optical Neutrino Telescopes
Dumand
Nemo
Lake Baikal
Antares
Nestor
KM3Net
AMANDA / IceCube
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The IceCube Collaboration
University of Alaska, Anchorage University of
California, Berkeley University of California,
Irvine Clark-Atlanta University University of
Delaware / Bartol Research Institute University
of Kansas Lawrence Berkeley Natl.
Laboratory University of Maryland Pennsylvania
State University Southern University and AM
College University of Wisconsin,
Madison University of Wisconsin, River
Falls Universität Dortmund MPIfK
Heidelberg Humboldt Universität,
Berlin Universität Mainz DESY, Zeuten BUGH
Wuppertal RWTH Aachen
Stockholms Universitet Uppsala Universitet Vrije
Universiteit Brussel Université Libre de
Bruxelles Universiteit Gent Université de
Mons-Hainaut Chiba University University of
Canterbury, Christchurch Universiteit
Utrecht Oxford University
Team South Pole
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Amundsen Scott South Pole Station
South Pole
IceCube
Living facilities
Skiway
Road to work
AMANDA
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The IceCube Detector
Instrumenting 1km3 of Antarctic Ice to detect
extraterrestrial neutrinos
IceTop
Surface air shower array
InIce
70 strings, each with 60 digital optical
modules (DOM) 17 m between modules 125 m string
separation
IceCube is sensitive to neutrinos of all flavors
at energies from 1011 eV to 1020 eV
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Digital Optical Module (DOM)
Digital Optical Module (DOM)

• Measure individual photon arrival time
• 2 ping-ponged four-channel Advanced Transient
  Waveform Digitizers
• 128 samples (400 ns
• max range)
• 3.3ns bin
• 400 pe / 15 ns
• Fast Analog-to-Digital
• Converter
• 40 MHz
• 6.4 ?s range

Ø32.5 cm

• Dark Noise rate 700 Hz
• Local Coincidence rate 15 Hz
• Deadtime lt 1
• Signal digitized in the ice

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IceCube Deployments to Date
78
74
73
72
67
77
66
2004-2005 1 string deployed First
data astro-ph/0604450
76
65
75
71
58
70
69
57
68
56
64
59
63
48
62
47
61
60
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AMANDA
55
54
50
49
2005-2006 8 string deployed
53
52
45
40
39
44
38
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2006-2007 13 strings deployed
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2007-2008 18 strings deployed and commissioned
50 of full detector installed (40 strings to
date) Completion by 2011!
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Muon bundle from interaction of a high-energy
cosmic ray in the atmosphere
IceCube real-time event viewer at pole
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IceCube Data Quality Assurance

• Example Use in situ remotely-controllable LEDs
  and downward-going muons to check relative DOM
  timing
• DOMs have individual free-running clocks
• clocks must be calibrated to within several ns to
  allow us to reconstruct events
• figure shows example of how this works with LEDs

Timing excellent on all new DOMs
Dt
Timing stable over gt1 year period
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18 new strings

• As IceCube is a newly constructed detector, we
  first verify the detector performance in order to
  achieve physics goals
• Stability and performance verified
• Very successful deployment season this year
• New strings seem to be working fine
• IceCube 50 complete
• IC-40 physics run will start end of April

Relative sensor efficiency
Time between Events
Nucl.Phys.B, Proc.Suppl.175-176409-414,2008.
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Integrated Exposure

• 1 km3yr by early 2009
• Close to 4 km3yr after one year of operations
  with full detector

Full IceCube ?
IC36-40
IC22
IC9
KM3NeT
AMANDA ANTARES
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Scientific Scopes
?
MeV
Supernovae
Average increase in the PMT counting rate
TeV-PeV
Point sources (AGNs, GRBs, MQs) and Diffuse
Up-going muons and cascades
PeV-EeV
AGNs, TDs, GZK neutrinos
Almost horizontal events
EeV
?
Down-going
Energy
Physics
Signature
GeV-TeV
Neutralino Atmospheric ?
Up-going muons Contained events
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Alien signals ?
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IC9 - Diffuse Analysis
Comparison of atm. muon neutrino predictions to
data

• Atmospheric neutrinos behave like E-3.7
• Typical extraterrestrial fluxes behave like E-2
  

IceCube-9 2006 data Lifetime 137days E-2 lt
1.3x10-7GeVcm2s-1sr-1
AMANDA-II 2000-2003 data Lifetime 807days E-2 lt
7.4x10-8GeVcm2s-1sr-1 Phys Rev. D76, 042008 (2006)
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Limit on diffuse extraterrestrial fluxes
AMANDA HE analysis Baikal IceCube 9
137days AMANDA-II 4yr IceCube muons, 1
year Icecube, muons cascades 4 years
2003 2006 2009 2013
WB Limit
GRB (WB)
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Neutrinos from GRBs

• Search time window from 10 sec before the burst
  start to the end of the burst.
• Precursor from -110 sec to -10 sec.
• Background estimation from 1 hour before to 1
  hour after (except 10 minutes around the burst)

10-7
Check for coincidences with BATSE, IPN, SWIFT
AMANDA limit from 408 bursts
1997-2003
10-8

• close to WB
• within lt factor 2
• with IceCube
• test WB within
• a few months

Waxman-Bahcall GRB prediction
E?2?flux (GeV?cm-2?s-1?sr-1)
10-9
10-10
104
106
105
107
108
neutrino energy E? (GeV)
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AMANDA Point Source Analysis
Signal hypothesis ? E-2
Optimal search window
2000-2004 4282 up-going 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

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Grid search for neutrino point sources ... Limit
map

• 90 confidence level flux upper limits for the
  northern hemisphere (15 systematic error
  included)

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Search for neutrinos from candidate objects
event selection optimized for both dN/dE E-2 and
E-3 spectra
source nr. of n events (5 years) expected background (5 years) E-2 flux upper limit (90 c.l.) 10-11 TeV-1 cm-2 s-1
Markarian 421 6 7.4 7.4
M87 6 6.1 8.7
1ES 1959650 5 4.8 13.5
3C 273 8 4.72 18.0
SS433 4 6.1 4.8
Cygnus X-3 7 6.5 11.8
Cygnus X-1 8 7.0 13.2
Crab Nebula 10 6.7 17.8

• out of 32 sources in candidate list
• No significant excess, no indication for a
  neutrino source
• Systematic error on signal prediction included in
  limits

No significant excess observed
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1st IceCube Sky Map
preliminary
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Dark Matter

• Strong observational evidence for dark matter
• Rotational profiles
• Gravitational lensing
• Large scale structures
• WMAPs measurement anisotropy measurement of the
  cosmic microwave background
• Characteristics of Dark Matter (DM)
• Stable
• Non baryonic
• Non relativistic
• Weakly interacting particle
• -gt Weakly Interacting Massive Particles
• In low energy SUSY with R-parity conserved, the
  Neutralino is an excellent candidate for dark
  matter

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WIMPs

• Massive bodies could gravitationally trap Dark
  Matter
• The Sun could capture WIMPs directly
• WIMPs orbiting the sun could be captured by the
  Earth
• Neutralinos could accumulate in the center of
  these massive bodies and annihilate to produce
  neutrinos as part of the annihilation products
• Neutrino Telescopes can search indirectly for DM
  by detecting these neutrinos

Solar capture rate
Annihilation rate (for equilibrium)
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WIMPs signal
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Earth WIMPs
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Earth WIMPs

• No statistically significant excess of neutralino
  induced neutrinos from the center of the Earth
• AMANDA limits competitive with other indirect
  searches
• AMANDA String trigger essential for low energy
  sensitivity
• More data being analyzed now

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Solar WIMPs
Earth
Cosmic Rays ????????????
nm
Analysis Strategy Scramble azimuth and use
entire dataset for cuts optimization Off-source
data to predict background
Detector
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Solar WIMPs
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Solar WIMPs

• No statistically significant excess of neutralino
  induced neutrinos from the center of the Sun
• AMANDA limits competitive with other indirect
  searches
• AMANDA String trigger essential for low energy
  sensitivity
• More data being analyzed now

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Contained and Partially contained events

• AMANDA
• Fully integrated detector
• Combined trigger / event builder
• New AMANDA DAQ has lower energy threshold
• 7 IceCube 18 AMANDA strings form a densely
  instrumented Inner Core
• Lower energy threshold
• Peripheral IceCube strings form veto volume
• Especially useful for physics with contained and
  partially-contained events

Inner Core
m
nm
veto
IceCube 07
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Atmospheric Muon Neutrino Sensitivity
Atmos. ?? per 200 days (trigger
level, IC22AMANDA)

• AMANDA forms more densely instrumented sub-array
  inside IceCube
• Lower energy threshold
• Contained events
• Increased WIMP sensitivity has been achieved
  using this method

Gross, Tluczykont, Ha, Rott, DeYoung,
Resconi, Wikström, ICRC 2007
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Solar WIMP Sensitivity
AMANDA limits astro-ph/ 0508518
current AMANDA-II 2001
soft decay spectrum
hard spectrum
Expected sensitivity with IC22 AMANDA
G. Wikström ICRC 2007
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Combined IceCube AMANDA Detector

• Improved angular resolution

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Atmospheric Neutrinos in IceCube

• 9-string data (2006)
• Cosmic ray background seen with weak cuts
• Atmospheric neutrinos seen with strong cuts
• Agreement in event rate over 6 decades

downward muons
Final Cuts
atmos.neutrinos
Achterberg et al. astro-ph/0705.1781
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IceCube String Trigger Sensitivity

• Topological trigger allow to lower the energy
  threshold further compared to the default
  multiplicity 8 trigger
• Selects events based on a certain pattern present
  in the detector
• IceCube geometry especially sensitive to vertical
  events
• String Trigger selects events
  
  consistent with vertically
  up/down-going
  muons
• String Trigger essential for
• Dark Matter searches
• Earth Wimps
• Halo Wimps
• Neutrino Oscillations

30GeV
??
Detectable events were defined as events that
have at least one hit in the detector
40
?m disappearance

• Lowest energy threshold is realized in vertical
  events
• Reconstruction might be possible for those events
  due to the IceCube geometry
• Elt30 GeV reachable with vertical muons
• 17m spacing in z-dimension
• muon travels 5 m/GeV
• need at least 5 DOMs 68 m
• E?,min 68/5 14 GeV (E?,min 25 GeV)?
• ?up/?down could be used for normalization
• difficult due to background contributions,
  directionality DOMs (face down)
• Related idea discussed in Albuquerque and Smoot,
  PRD.64.053008
• issues
• Kinematic ?-? angle
• flat inelasticity (y) distribution
• Atmospheric muon background

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• Kinematic angle smears out directional
  information of low energy neutrinos
• Does not really effect study of first oscillation
  maximum

Muon neutrino survival probability
En lt 100GeV String triggered
Akhmedov, Maltoni Smirnov, hep-ph/0612285
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Why study neutrino oscillations in IceCube now ?

• Never been observed (tested) at the energy range
  accessible to IceCube (E?? 20-50 GeV)?
• Actual observation of a signal
• Energy reconstruction especially challenging,
  this can also serve as a cross-calibration
  measurement
• 40km of strings available now
• Several thousand high quality low energy
  vertical neutrinos events per year

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Low energy extensions of IceCube
0m 1500m 2100m 2500m

• Funding for 6strings recently approved. Shows
  clear interest in 10-100GeV Neutrino physics
• Favored design
• 6 strings each with 60 DOMs, spaced by 10 m
  (final geometry choice end of April)
• located in best ice (below 2100 m exceptionally
  clear)
• Large veto region from top and surrounding
  strings against down-going muons -gt 4pi
  steradians
• uses IceCube technology but HQ PMTs

AMANDA
deep core
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Low Energy Extensions

• Forms dense sub-array
• Large veto region can more effectively remove
  down-going muon background
• Considerably better performance at low energies
• Would be deployed in the deep ice
• Lower atmospheric muon background
• Clear ice (below 2100m)
• Effective Veto from surrounding IceCube strings
  and DOMs above

Veto region
First string end of this year !
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Physics with Deep Core

• 4 Pi detector and 24 h
• Wimp improvements
• Galactic Centre - Galactic plane
• Low energy atmospheric neutrinos
• Oscillations
• Neutrino Tomography
• Cascade direction and reconstructions
• Atmospheric electron neutrino spectrum
• Staus
• Monopoles

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Neutrino Mass Hierarchy

• Matter effects enhance the oscillation
  probability for (anti-)neutrinos if the mass
  hierarchy is normal (inverted)
• In the relevant energy range the anti-neutrino
  cross-section is smaller than that of neutrino by
  roughly a factor of 2

hep-ph/08033044
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Neutrino Mass Hierarchy
Normal hierarchy Inverted hierarchy
Vertical tracks 10 years exposure
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Conclusions

• IceCube finished phenomenal season 07/08 with 18
  new strings deployed
• AMANDA and IceCube are operating jointly and
  collecting data
• First physics results of IceCube already
  competitive with AMANDA
• Dataset especially interesting towards low energy
  analysis
• New searches for WIMPs, Neutrino Oscillations,
  ... underway
• Studies towards new deeper low energy core
  ongoing design choices to be made in about a
  month
• many more exciting results to come (Neutrino 08)

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Backup Slides
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IceCube n Flavor Separation
nt
full flavor ID
ne
Neutrino flavor
ne
(supernovæ)
showers vs. tracks
nm
12
18
21
9
15
6
Log(E/eV)
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WIMPs Sensitivity
Earth
Sun
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Observations in the direction of 1ES 1959650
An interesting coincidence with a gamma ray
flare 3.7 atmospheric neutrino events expected
between 2000 and 2003. 5 events observed, incl.
3 in 66 days in 2002, during active period of
source
Orphan flare (MJD 52429)
Whipple light curve Holder et al 2003
AMANDA events within 2.25o of the direction of
1ES 1959650
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Supernova Neutrino Search
SNEWS (SuperNova Early Warning System) is a
collaborative effort among Super-K, SNO, LVD,
KamLAND, AMANDA, BooNE and gravitational wave
experiments
Count rates
Simulation (IceCube)
O(10cm) long tracks