Neutrino Astronomy at the South Pole Searches for astrophysical high-energy neutrinos with IceCube...
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Neutrino Astronomy at the South PoleNeutrino Astronomy at the South Pole
Searches for astrophysical Searches for astrophysical high-energy neutrinos high-energy neutrinos
with IceCubewith IceCubeKurt WoschnaggKurt Woschnagg
UC BerkeleyUC Berkeley
Miami 2012Miami 2012Lago Mar, Ft Lauderdale, December 18, 2012Lago Mar, Ft Lauderdale, December 18, 2012
p + p → π + … → ν + …
or, if Ep > 6×1019 eV,
p + γCMB → Δ → π + n → ν + …
Neutrinos and the Origin of Cosmic RaysCosmic ray spectrumCosmic ray spectrum
Galactic: SN remnants
Extragalactic: AGNs / GRBs / Other
We expect high-energy neutrinos from the same sources:
ankle
1 particle/(km2yr)
knee
1 particle/(m2 yr)
1 particle/(m2s)
Greisen, Zatsepin, and Kuzmin (1966)
GZK cutoffHillas 2006, arXiv:astro-ph/0607109v2
Rate = Neutrino flux x Neutrino Effective Area = Neutrino flux x Neutrino Cross Section x (1 - Absorption in Earth) x Size of detector x (Range of muon for )
S.K
lein
, F
. H
alze
n, P
hys.
Tod
ay,
May
200
8
vertical
horizontal
Expected GZK neutrino rates in 1 km3 detector: ~ 1 per year
Size matters: need for a km3 neutrino detector
Eff
ectiv
e ar
ea (
m2)
IceCube footprintGeographical South Pole
Drill Camp
DeepCorefootprint
Skiway
Counting houseCounting house
Amundsen-Scott Station (US)
The IceCube Neutrino Observatory
Digital Optical Module (DOM)
Configurationchronology
2006: IC9 2007: IC22 2008: IC40 2009: IC59 2010: IC79 2011: IC86
Completed: Dec 2010
DeepCore8 strings – spacing optimized for lower energies480 optical sensors
PMT
Talk by Ty DeYoung
Neutrino Detection Principle
Observe the charged secondaries via Cherenkov radiation detected by a 3D array of optical sensors
ν
, ν
hadronicshower
W, Z
Need a huge volume (km3)of an optically transparentdetector material
Antarctic ice is the most optically transparent natural solid known(absorption lengths up to 200+ m)
Ice to meet you, neutrinos!But: optical properties depend on depth due to variations in dust concentration:Absorption in ice is weakest where
the optical module sensitivity peaks:
Background Rejection
Atm.
Atm.
Up-goingDown-going
Muons: 2800 HzNeutrinos: 1 per 10 minNeed 106 background rejection
Tracks
pointing resolution ~1o
N X
Cascades
energy resolution 10% in log(E)
Composites starting tracks tau double bangs good directional and energy resolution
e( ) N e( ) X f N f X f = e, ,
e-m and hadronic cascades
Neutrino Event Signatures
This talk
Next talk
Moon shadow seen with ~14 Systematic pointing error < 0.1o
Verification of PSF for track reco.
on-source
preliminary
In the Shadow of the Moon IC59
Need high statistics and good angular resolution!
Cosmic rays blocked by the moon cause point-like deficit in angular distribution of down-going muons in the detector
off-source“left”
off-source“right”
Neutrino Fluxes: atmospheric νμ
cosmogenic (GZK) ν
Stecker AGN (Seyfert)
Phys. Rev. D83 (2011) 012001Phys. Rev. D84 (2011) 082001
Neutrino Fluxes: atmospheric νe
cosmogenic (GZK) ν
Stecker AGN (Seyfert)
Next talk:
Mariola Lesiak-Bzdak
Phys. Rev. D83 (2011) 012001Phys. Rev. D84 (2011) 082001
Atm.
Atm.
Search for an excess of astrophysical neutrinos from a common direction over a background of atmospheric neutrinos
Search for Neutrino Point Sources
All-Sky Point Source Search IC40+IC59+IC79
108,317 upgoing events → >100,000 neutrinos146,018 downgoing events
Livetime: 316 days (IC79) 348 days (IC59) + 375 days (IC40)
Northern Sky (below the horizon)Data dominated by atmos. ’s
E ~ 10’s - 100’s of TeV
Southern Sky (above the horizon)Data dominated by atmos. ’sE > PeV, increasing with angle
E-2 neutrino simulation
atm
osph
eric
at
mos
pher
ic
significance
All-Sky Point Source Search IC40+IC59+IC79
For each event/direction (previous slide), take PSF from reconstruction and background estimate and add up to make this significance map.
atm
osph
eric
at
mos
pher
ic
significance
All-Sky Point Source Search IC40+IC59+IC79
-log10p = 4.707nSrcbest = 23.07best = 2.35
Highest significance inazimuthally scrambledskymaps (2000 trials)
Hottest spot in Northern sky (Ra=34.25, Dec=2.75)
Not significant: 57% of trials have significance ≥ hottest spot
atm
osph
eric
at
mos
pher
ic
significance
All-Sky Point Source Search IC40+IC59+IC79
-log10p = 4.707nSrcbest = 23.07best = 2.35
Hottest spot in Northern sky (Ra=34.25, Dec=2.75)
Not significant: 57% of trials have significance ≥ hottest spot
Highest significance inazimuthally scrambledskymaps (2000 trials)
atm
osph
eric
at
mos
pher
ic
significance
All-Sky Point Source Search IC40+IC59+IC79
-log10p = 4.047nSrcbest = 20.81best = 3.75
Hottest spot in Southern sky (Ra=219.25, Dec=-38.75)
Not significant: 98% of trials have significance ≥ hottest spot
Highest significance inazimuthally scrambledskymaps (2000 trials)
atm
osph
eric
at
mos
pher
ic
significance
All-Sky Point Source Search IC40+IC59+IC79
Highest significance inazimuthally scrambledskymaps (2000 trials)-log10p = 4.047
nSrcbest = 20.81best = 3.75
Hottest spot in Southern sky (Ra=219.25, Dec=-38.75)
Not significant: 98% of trials have significance ≥ hottest spot
Point Source Limits IC40+IC59
Upper limits on an E-2 neutrino flux from pre-selected list of astrophysical objects (Blazars, SN remnants, etc)
Atm.
Atm.
Energy
Atmospheric ,
Harder Spectrum (E-2)
Astro.
Search for excess of astrophysical neutrinos with a harder spectrum than background atmospheric neutrinos
Advantage over point source search: can detect weaker fluxes
Disadvantages: high background must simulate background precisely
Sensitive to all three neutrino flavors
Diffuse Flux = effective sum from all (unresolved) extraterrestrial sources (e.g., AGNs)Possibility to observe diffuse signal even if flux from any individual source is too weak for detection as a point source
Searches for a Diffuse Neutrino Flux
Attempt to distinguish classes of neutrinos in two dimensions:
Search for a diffuse muon neutrino flux IC59
Energy
Arrival angle
Use reconstructed energy loss as energy estimator
~1° resolution(better for higher energies)
Search for a diffuse muon neutrino flux IC59Two-dimensional likelihood fit to final neutrino sample (21,943 events, <0.2% background muons) PDFs for three neutrino classes (from simulations):
Astrophysical: E-2
Conventional: Honda et al., Phys. Rev. D, 75, 043006 (2007) Prompt: Enberg et al., Phys. Rev. D, 78, 043005 (2008)Increased sensitivity to E-2 flux by inclusion of CR knee (Gaisser)
Search for a diffuse muon neutrino flux IC59
The highest energy event in the final sample:
Best-fit results:E-2 norm = (0.027 + 0.059) ×10-7 E2 GeV cm-2 s-1 sr-1
Prompt norm = (0 + 1.216) × [Enberg et al. + Gaisser knee]
Limits on a diffuse muon neutrino flux IC59Experimental upper limits on the diffuse flux of muon neutrinos from sources with ~ E-2 energy spectrum
Neutrinos from Gamma Ray Bursts
Fireball model:Internal shocks in GRBs → acceleration for UHECRsNeutrino production in p-γ interactions in fireball
Neutrinos from Gamma Ray Bursts IC40+IC59
Nature 84, 351 (2012)
215 GRBs in Northern sky
2 events observed: both trigger IceTop so likely atmospheric muons
Neutrino flux limits in tension with fireball model
Search for neutrinos from direction of GRB in short time window (<±1 day) around trigger time (=satellite measurement of GRB):
Neutrino and Dark Matter Physicswith IceCube DeepCore
Tyce DeYoungDepartment of PhysicsPennsylvania State University
Miami 2012Fort LauderdaleDecember 18, 2012
Selected slides from
IceCube DeepCore
• A more densely instrumented region at the bottom center of IceCube
• Eight special strings plus 12 nearest standard strings
• High Q.E. PMTs
• ~5x higher effective photocathode density
• In the clearest ice, below 2100 m
• λatten ≈ 45-50 m
• IceCube provides an active veto against cosmic ray muon background (around 106 times atmospheric neutrino rate)
250 m
35
0 m Deep
Core
extraveto cap
AMANDA
IceCube
scattering
Tyce DeYoung Miami 2012 December 18, 2012
IceCube DeepCore
•Original IceCube design focused on neutrinos with energies above a few hundred GeV
•DeepCore provides ~25 MTon volume with lower energy threshold
• Higher efficiency far outweighsreduced geometrical volume
• Note: comparison at triggerlevel – analysis efficienciesnot included (typically ~10%)
•O(105) atmospheric neutrinotriggers per year
Sun
Silk, Olive and Srednicki, ’85Gaisser, Steigman & Tilav, ’86
Freese, ’86Krauss, Srednicki & Wilczek, ’86 Gaisser, Steigman & Tilav, ’86
et alia
velocitydistribution
ν interactions
annihilation channels
Indirect Detection of Dark MatterIndirect Detection of Dark MatterSimilar accumulation in Galactic and terrestrial gravitational wells,
dwarf spheroidals
IceCube can also probe dark matter decay models, other types of dark matter
ρ
σscatt
Γcapture
Γannihilation
νμ
μ
Expected Neutrino Energy Spectrum
•All neutrinos from the Sun are low energy for IceCube (few hundred GeV), even for the highest dark matter masses
• For Galactic and Earth searches, little neutrino energy loss in the source, so higher energy neutrinos possible – lower threshold probes lower mχ
5 TeV χ → W+W–5 TeV χ → bbK
Solar WIMP Search
Three event selections applied to 2010 data set: high energy, low energy (winter), and low energy (summer ~ downgoing)
After selection, uselikelihood analysisto constrainmagnitude ofsimulated WIMP signal in sky map
simulated signal (e.g., mχ = 1 TeV)
data and off-source background expectation
angular separation from Sun
Preliminary Results
•Actual limits on SD scattering and annihilation via soft and hard channels, compared to expected limits
• (A signal wouldappear as anupward deviationfrom the yellowband)
•No evidence forneutrino flux fromsolar WIMPs
Preliminary Results
•IceCube and other limits on SD χN scattering cross section
•Blue shadedregion showsMSSM modelspace not incontradiction to CDMS,XENON, andLHC limits
• Both SD andSI limits onSUSY modelsincluded
Tyce DeYoung Miami 2012 December 18, 2012
Neutrino Oscillations
•Energy scale of oscillationphenomena is set by neutrino energy and range of baselines
•For neutrino path lengthequal to Earth’s diameter:
• First oscillation maximumaround 24 GeV
• Hierarchy-dependentmatter effects below10 GeV – too low for DeepCore
•At these energies, DeepCore dominates the IceCube response
νμ disappearance
ντ appearance
Mena, Mocioiu & Razzaque, Phys. Rev. D78, 093003 (2008)
Tyce DeYoung Miami 2012 December 18, 2012
Muon Disappearance
•As a first step, compare zenith-dependent response of standard IceCube muon analysis (high energy) to a modified version for DeepCore
• Look for oscillationsignature in eventrate suppression atlow energies
• Detector systematicsreduced by comparingHE and LE rates
• Based on traditionalmuon analysis, no newtechniques designed forDeepCore – lower efficiency accepted
Muon Disappearance
Statistically significant angle-dependent suppression at low energy
• Shaded bands show range of uncorrelated systematic uncertainties; overall normalization uncertainty shown at right
Muon Disappearance
•Oscillation parameterallowed regions extractedfrom zenith distributions
• Systematics included
•Preliminary results inexcellent agreementwith world averagemeasurements (withlarge uncertainties)
• Potential for significantimprovement with inclusionof energy estimators, moreadvanced reconstructions and event selections
SummaryEra of km3 neutrino astronomy has begun
100,000+ high-energy neutrinos on the books
No astrophysical neutrino sources detected yetNo neutrinos seen from GRBs
Setting limits on physics of fireball model
Continued gains in sensitivityDetector size, data taking, analysis techniques
Low energy neutrino physics with DeepCoreAtmospheric oscillations
Lots of physics to come:cosmic ray spectrum cosmic ray composition cosmic ray anisotropies atmospheric neutrinos (prompt
component, oscillations, effects of quantum gravity, sterile neutrinos, … ) neutrino point sources gamma ray bursts GZK neutrinos multimessenger approaches diffuse fluxes dark matter
magnetic monopoles supernova bursts shadow of the moon atmospheric physics glaciology climatology new technologies for highest energies (radio, acoustics)
Canada University of Alberta
US Bartol Research Institute, Delaware Pennsylvania State University University of California - Berkeley University of California - Irvine Clark-Atlanta University University of Maryland University of Wisconsin - Madison University of Wisconsin - River Falls Lawrence Berkeley National Lab. University of Kansas Southern University, Baton Rouge University of Alaska, Anchorage University of Alabama, Tuscaloosa Georgia Tech Ohio State University
Sweden Uppsala Universitet Stockholms Universitet
UK Oxford University
Belgium Université Libre de Bruxelles Vrije Universiteit Brussel Universiteit Gent Université de Mons-Hainaut
Switzerland EPFL, Lausanne Université de Genève
Germany Universität Mainz DESY-Zeuthen Universität Dortmund Universität Wuppertal Humboldt-Universität zu Berlin MPI Heidelberg RWTH Aachen Universität Bonn Ruhr-Universität Bochum
JapanChiba University
New Zealand University of Canterbury
ANTARCTICAAmundsen-Scott Station
http://icecube.wisc.edu
37 institutions, ~250 members
The IceCube Collaboration
Australia University of Adelaide