searching for dark matter with icecube { Sven Lafebre - - PowerPoint PPT Presentation

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searching for dark matter with icecube

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Sven Lafebre Pennsylvania State University Rencontres de Moriond March 2010

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amundsen-scott station

Station South Pole Skiway IceCube lab IceCube drill camp

(photo: henry malmgren)

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the icecube observatory

Lab DeepCore

IceCube

• Cubic km detector volume
• 1450–2450 m depth
• 125 m string spacing
• 17 m sensor spacing

DeepCore

• 70 m string spacing
• 7 m sensor spacing

IceTop

• Surface cosmic ray detector

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digital optical module

Photomultiplier

• 10” Hamamatsu

18% quantum eff. at 400 nm Digitizers

• ATWD

3 gain channels 300 MHz sampling 400 ns recording time

• ADC

40 MHz sampling 6.4 ms recording time

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detection principle

• Neutrinos interact in or near

detector

• Tracks from charged-current

νµ interactions: km scale

• Cascades from other interactions

(neutral-current, νe, ν): 10 m scale

• Detect Cherenkov radiation

ν µ

νi

W, Z i, νi

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neutrino signatures

Tracks

• Through-going muons
• 1º pointing resolution

Cascades

• Neutral current
• Charged current νe, ν
• 10% resolution in

log(energy) Composites

• Starting tracks,

double bangs

• Good directional and

energy resolution

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pointing resolution

22 strings: 1.5º 40 strings: < 1.0º 80 strings: < 0.5º

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pointing resolution

22 strings: 1.5º 40 strings: < 1.0º 80 strings: < 0.5º

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See arXiv:1002.4900

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background & filtering

Simulated muon fluxes

• Atmospheric muons

from above

• Atmospheric neutrinos

from all directions

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science overview

Diffuse and point source searches active galactic nuclei, supernovae, gamma ray bursts, dark matter Use ‘background’ as signal cosmic rays & atmospheric neutrinos Exotic and other phenomena monopoles, supersymmetry & glaciology

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how to look for dark matter

• Dark matter amasses in heavy objects

(Sun, Galactic Center)

• Look for neutrinos produced in self-

annihilation (GeV–TeV scale) χ

νµ

ll qq W±, Z, H

χχ χχ χχ χχ

νµ νµ νµ νµ

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Trigger South Pole Angular cuts Track quality Advanced cuts Efficiency 10–2 10–4 10–6 1

Filtering steps:

• Initial trigger
• Quality cut at South Pole
• Angular cuts
• Track reconstruction

quality cut

• Advanced cuts:

log likelihood, decision trees, support vector machines

wimps in the sun

Atmospheric νµ Signal (1 TeV hard) Total background Data Passing rates, 22 strings

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wimps in the sun

• IceCube 22: 104.3 days

amanda: 150.4 days

• Blind analysis

hide Sun azimuth

• Select zenith 90º–120º

Sun below horizon

• Remove muon background
• 20% signal efficiency
• 4º angular resolution
• bserved flux is consistent with background expectations

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Neutralino mass (GeV) 10

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3

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Neutralino-proton SD cross-section (cm

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CDMS(2008)+XENON10(2007)

lim SI

• <

SI

• < 0.20

2

h

• 0.05 <

CDMS (2008) COUPP (2008) KIMS (2007) SUPER-K 1996-2001 IceCube-22 2007 (soft) IceCube-22 2007 (hard)

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2

10

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Soft Hard

wimps in the sun

• Muon flux limit

probes spin- dependent neutralino-proton cross-section

• Dependent on

models of dark matter density distribution and annihilation modes

• Hard: W+W–

Soft: bb

Allowed mssm models prl 102, 201302 (2009)

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Neutralino mass (GeV) 10

2

10

3

10

4

10 )

2

Neutralino-proton SD cross-section (cm

• 41

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• 39

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CDMS(2008)+XENON10(2007)

lim SI

• <

SI

• < 0.20

2

h

• 0.05 <

CDMS (2008) COUPP (2008) KIMS (2007) SUPER-K 1996-2001 IceCube-22 2007 (soft) IceCube-22 2007 (hard)

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2

10

3

10

4

10

• 41

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Soft Hard

wimps in the sun

• Muon flux limit

probes spin- dependent neutralino-proton cross-section

• Dependent on

models of dark matter density distribution and annihilation modes

• Hard: W+W–

Soft: bb

Allowed mssm models prl 102, 201302 (2009)

(Primary Neutrino Energy - GeV)

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log 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 )

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E f f e c t i v e N e u t r i n

• A

r e a ( m

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10

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Preliminary

8 s t r i n g s 80 strings + DeepCore

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wimps in the sun

Kaluza-Klein dark matter

• 5 universal space-time

dimensions

• Lightest kk particle (lkp)

mass is 0.3–1.0 TeV

• In equilibrium in the Sun
• Annihilate to standard-

model particles

• Result uses same dataset as

‘traditional’ wimp search

See arXiv:0910.4480, prd accepted

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wimps in the galaxy

• Galactic Halo extends below

horizon

• Compare equal areas on-source

and off-source

• Measure flux difference,

pick models, and constrain self-annihilation cross-section

On-source Off-source Galactic Center dΦ dE = 1 2⟨σAv⟩J(ψ) R⊙ρ2

⊙

4πm2

χ

dN dE

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wimps in the galaxy

• 90% confidence exclusion

limit

• Width derives from various

density models

See arXiv:0912.5183

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10−26 10−24 10−22 10−20 10−18 102 103 104 <σA v> [cm 3s−1] m [GeV]

natural scale unitarity bound bb bb WW WW

• µµ

µµ NFW halo model IceCube 40 (GC) IceCube 22 (outer Galaxy)

Halo Model Uncertainty

p r e l i m i n a r y

Limits (90% C.L.) on the self annihilation cross section ( -> bb, WW, µµ, )

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conclusion

• Construction ends next year
• 79 strings in the ice;

taking data starting April 1

• 22-string analyses limit spin-

dependent cross-sections

• 40-string analyses are

underway

• 59-string data available soon
• DeepCore boosts wimp

sensitivity below 100 GeV

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thank you

The IceCube Collaboration

36 institutions { 250 physicists

• U. of Alberta
• U. of West Indies
• U. Alabama, Tuscaloosa
• U. Alaska, Anchorage

U.C. Berkeley Clark-Atlanta U.

• U. Delaware/Bartol Inst.

Georgia Tech U.C. Irvine

• U. of Kansas

Lawrence Berkeley Nat. Lab

• U. of Maryland

Ohio State U. Pennsylvania State U. Southern U., Baton Rouge

• U. of Wisconsin-Madison
• U. of Wisconsin-River Falls

RWTH Aachen

• U. Bonn

Vrije U. Brussel

• U. Libre de Bruxelles

DESY, Zeuthen

• U. Dortmund
• U. Gent

MPI Heidelberg Humboldt U., Berlin

• U. Mainz
• U. de Mons-Hainaut

Oxford U.

• RuhrU. Bochum

Stockholm U. Uppsala U.

• U. Wuppertal

Chiba U.

• U. of Canterbury, Christchurch

EPF Lausanne