searches for dark matter with the · icecube can test dm models motivated by pamela & fermi...

Matthias Danninger for the IceCube CollaborationThe Oscar Klein Centre for Cosmoparticle Physics, Dep. of Physics Stockholm University

Searches for Dark Matter with the IceCube detector

12th International Conference on Topics in Astroparticle and Underground Physics, 5 – 9 September 2011, Munich, Germany

05/09/11 Matthias Danninger TAUP 2011 2

IceCube detector

AMANDA19 stringsUntil 2009

DeepCore8 add. densely instrumented strings

Detailed detector description, see IceCube plenary talk on Thursday

IceCube86-strings

✗ O(km) muon tracks from νµ CC

✗ O(10m) cascades from νe CC, low energy ντ CC, and νx NC

✗ Cherenkov radiation detected by3D array of optical sensors (DOMs)


Indirect Search with IceCube

Sun: Limits form AMANDA, IC22, IC40+AMANDA → IceCube-79 imminent

Galactic Center & Halo:Limits from IceCube-22, IceCube-40 → IceCube-79 under-way

Earth:Limits from AMANDA

Dwarf Galaxies:→ IceCube-59 & IceCube-79 under-way

Searches beyond “ standard” SUSY:Limits on Simpzillas→ secluded dark matter sector under-way

,ν

ν

SD limits mχ>50GeV more stringent than of direct searches (up to factor 100)


Indirect Search with IceCubeVery brief recap:(1) Halo WIMPs scatter on nuclei in the Sun/Earth(2) Some lose enough energy in the scatter to be gravitationally bound(3) Scatter some more, sink to the core(4) Annihilate with each other, producing neutrinos

(5) Propagate+oscillate their way to the South Pole, convert into muons in CC interactions

(6) Look for Cerenkov radiation from the µ ,ν,e⁺⁽⁻⁾

ν

WIMP candidates:✗ MSSM: (LSP) neutralino, m(χ0

1)[35 GeV – 5 TeV]

Hard channel (τ+τ− / W+W-) Soft channel (b b)✗ UED: (LKP), B( 1 ) or γ ( 1 )

fixed branching ratios: m(γ ( 1 ) [250 GeV–3TeV]


Analysis strategy:Look for an excess of events in the on-source region w.r.t. the off-sourceGalactic Center: ✗ on-source region below the horizon✗ need to veto downgoing muons.✗ Use central strings of detector as fiducial volume, surrounding layers as veto.

IC22 (Halo analysis – 275 days): observed on-source: 1367 evtsobserved off-source: 1389 evtsEvent selection dominated by atm. ν

IC40 (G-Center analysis – 367 days): observed on-source: 798842 evtsobserved off-source: 798819 evtsEvent selection dominated by atm. µ

Galactic-Center and Halo search

Observations in both analyses wereconsistent with background-only expectations

on-source off-source

GC


Limits computed at 90% C.L. as function of WIMP mass and for various annihilation channels assuming branching fractions of 100%

Galactic-Center and Halo limits

multi-wavelength approach to dark matter searches:IceCube can test DM modelsmotivated by PAMELA & Fermidata (e.g. Meade et al. 2008)

For more details on analysis and systematics discussions:Phys. Rev. D 84, 022004 (2011) (IC22)

ICRC 2011 (2011) (IC40)


IC40

Analysis Results from the Sun

details on SUSY-WIMP limits:Abbasi et al., PRL. 102, 201302 (2009) (IC22 result)ICRC 2011 (IC40+AMANDA result)ICRC 2011 (IC86 sensitivity)

Combined multi-year limit from AMANDA, IceCube-22 and IceCube-40+AMANDA dataTotal livetime of 1065 days

details on LKP limits:Abbasi et al., PRD 81 (2010) 057101. (IC22 result)

µ-flux lim

its LKP-limits

IceCube-hard

IceCube-soft

IceCube86 sens.

Super-K


New SUSY analysis with IceCube

What can the muon signal tell me?

Roughly:✗ Number – how much annihilation is going on in the Sun

⇒ info on σSD , σSI and <σv>✗ Spectrum – sensitive to WIMP mass mχ and branching

fractions BF into different annihilation channels χ✗ Direction – how likely it is that they come from the Sun

In model-independent analyses a lot of this information is either discarded or not given with final limits

Goal:Use as much of this information on σSD , σSI , <σv> , mχ and BF (χ ) as possible to directly constrain specific points and regions in WIMP model parameter spaces

IceCube Coll. together with:Pat Scott, Chris Savage,Joakim Edsjö

detailed presentation* (TeVPA11)

*Direct link: http://agenda.albanova.se./conferenceDisplay.py?contribId=396&sessionId=255&confId=2600

http://agenda.albanova.se./


DarkSUSY for computing neutrino fluxes:✗ No assumption of equilibrium between capture & annihilation, or ann. final state✗ Inclusion of perturbations to WIMP orbits by Jupiter✗ Full numerical capture treatment. SD and SI scattering on more isotopes, not just H¹✗ Full neutrino production, propagation and oscillation via tabulated WimpSim results✗ Explicit example models - lightest neutralino in SUSY (MSSM-7 and CMSSM)

SUSY model exclusion analysis

Compare observed number of events and predicted number for each model, taking into account systematic uncertainties and construct p-values

→ Model exclusion analysis


Global SUSY analysis with IceCube

✗ Only partial goodness of fit, no measure of convergence, no idea how to generalise to regions or whole space.

✗ Frequency/density of models in IN/OUT scans means essentially nothing.

Assuming preliminary (conservative) estimate of IC-86 effective area

prel

imina

ry


More information comes from a global statistical fit.→ parameter estimation exercise

Composite likelihood made up of observations from all over:✗ Dark matter relic density from WMAP✗ Precision electroweak tests at LEP & LEP limits on sparticle masses✗ B-factory data (rare decays, b → sγ)✗ Muon anomalous magnetic moment✗ LHC searches, direct detection (not yet included)


+ IceCube unbinned likelihood


SD nuclear scattering cross-section in the CMSSM with IceCube-22 events

✗ Contours indicate 1σ and 2σ credible regions✗ Shading+contours indicate relative probability only, not overall goodness of fit✗ Scans performed with modified SuperBayes 1.5.1 and unreleased DarkSUSY






prel

imina

ry


Closing remarks

✗ IceCube is complete & taking data with 86 strings since May 2011✗ Most recent results from 2008/09 (22/40 strings) are being released✗ Analysis on 79 strings are to be expected very soon

→ Incl. DeepCore (6 densely instrumented strings)→ 4π detector, enhanced veto capabilities → full year-round DM searches→ expected boost of sensitivity for low-mass WIMPs

✗ A framework for directly comparing event-level IceCube data to individual points in theory parameter spaces is in place→ The requisite tools will be available in DarkSUSY in the future→ Event data will eventually be released in a form digestible by the tools→ Direct SUSY analyses of IC79 data are on the way→ Many low-energy models exist


Additional Slides


Dark Matter candidates

• arise in extensions of the Standard Model• assumed to be stable: relics from the Big Bang• mass from few GeV to few TeV

candidates:

• MSSM: lightest super-symmetric particle (LSP) neutralino,

χ01 = z1 1B + z1 2W

3 + z1 3H0

1+ z1 4H02

simulation of “softest” and “hardest” case

hard: m(χ01) [35 GeV – 5 TeV] (τ+τ− / W+W-)

soft: m(χ01) [35 GeV – 5 TeV] (b b)

• Universal extra dimensions: Lightest Kaluza-Klein particle (LKP), B( 1 ) or γ ( 1 )

fixed branching ratios: m(γ ( 1 ) [250 GeV–3TeV]

RProbing higher energies in Galactic center & halo analysis


Dark Matter in the Milky Way:✗ Outer halo relatively well understood✗ inner halo still subject of debates (cusp or core

structure)✗ Can probe DM self-annihilation cross section

✗ Halo distribution✗ SUSY✗ Measurement

Galactic-Center and Halo search

e.g. IC40 event map

(χχ µ→ ⁺µ ,⁻ τ⁺τ ...)⁻


Limits computed at 90% C.L. as function of WIMP mass and for various annihilation channels assuming branching fractions of 100%

Galactic-Center and Halo limits

For more details on analysis and systematics discussions:Phys. Rev. D 84, 022004 (2011) (IC22)

arXiv 000000, ICRC 2011 (2011) (IC40)


Dark Matter Searches from the Sun

Analysis strategy:✗ Remove atmospheric muon events until data sample is dominated by atmospheric

neutrino events✗ signal events within IceCube may have low mean muon energy in detector

→ short tracks with few hits✗ cut on quality and reconstruction

parameters, maximizing horizontallow energy muon track selection(linear cuts & multivariate cuts)

✗ final data selection→ determine Veff & Aeff

final data sample dominated by neutrino events



Analysis strategy:✗ Remove atmospheric muon events until data sample is dominated by atmospheric

neutrino events✗ signal events within IceCube may have low mean muon energy in detector

→ short tracks with few hits✗ cut on quality and reconstruction

parameters, maximizing horizontallow energy muon track selection(linear cuts & multivariate cuts)

✗ final data selection→ determine Veff & Aeff

✗ DM searches directional: good additional handle on event selection → distribution-shape analysis Signal & background pdf's of Ψ: angle between

reconstructed track and direction of the Sun

Background

Signal



Combined multi-year limit from AMANDA, IceCube-22 and IceCube-40+AMANDA dataTotal livetime of 1065 days

ΓA

Cc~σSDΦµ Events close to the direction of the Sun

IC40


Analysis Results from the Sun

For more details:Abbasi et al., Physical Review D81 (2010) 057101. (IC22 result)ICRC 2011 contribution (2011) (IC40+AMANDA result)

limits & sensitivity:Only data, when Sun is below the horizon

main syst. uncertainty:Photon propagation in the ice & absolute DOM efficiency (~20%)

relate muon flux and WIMP - nucleon cross−section:


Dwarf Galaxy analysis prospects


searches from the Sun: Superheavy DM

searches for dark matter with the · icecube can test dm models motivated by pamela & fermi...

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