Neutrino Astronomy at the South Pole Searches for astrophysical high-energy neutrinos with IceCube...

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Searches for Searches for astrophysical astrophysical high-energy neutrinos high-energy neutrinos with IceCube with IceCube Kurt Woschnagg Kurt Woschnagg UC Berkeley UC Berkeley Miami 2012 Miami 2012 Lago Mar, Ft Lauderdale, December 18, Lago Mar, Ft Lauderdale, December 18, 2012 2012

Transcript of Neutrino Astronomy at the South Pole Searches for astrophysical high-energy neutrinos with IceCube...

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

Neutrinos as Cosmic Messengers

Cherenkovtelescope

Interstellarmolecular clouds

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: expectations

cosmogenic (GZK) ν

Stecker AGN (Seyfert)

Atmospheric

Astrophysical

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