{ searching for dark matter with icecube { Sven Lafebre Pennsylvania State University Rencontres de Moriond March 2010 {
amundsen-scott station Skiway Station IceCube drill camp IceCube lab South Pole (photo: henry malmgren)
the icecube observatory Lab 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 DeepCore IceTop • Surface cosmic ray detector 3
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 4
detection principle i, ν i ν i W, Z • Neutrinos interact in or near detector • Tracks from charged-current ν µ interactions: km scale • Cascades from other interactions (neutral-current, ν e , ν � ): µ 10 m scale ν • Detect Cherenkov radiation 5
neutrino signatures Tracks Cascades Composites •Through-going muons •Neutral current •Starting tracks, •1º pointing resolution •Charged current ν e , ν � double bangs •10% resolution in •Good directional and log(energy) energy resolution 6
pointing resolution { 22 strings: 1.5º 40 strings: < 1.0º 80 strings: < 0.5º 7
pointing resolution { 22 strings: 1.5º 40 strings: < 1.0º 80 strings: < 0.5º See arXiv:1002.4900 7
background & filtering • Atmospheric muons from above • Atmospheric neutrinos from all directions Simulated muon fluxes 8
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
how to look for dark matter • Dark matter amasses in heavy objects χ (Sun, Galactic Center) • Look for neutrinos produced in self- annihilation (GeV–TeV scale) ν µ χχ � ll � ν µ χχ � qq � ν µ χχ � W ± , Z, H � ν µ χχ � ν µ 10
wimps in the sun 1 Signal (1 TeV hard) Filtering steps: Atmospheric ν µ • Initial trigger Total background 10 –2 Efficiency • Quality cut at South Pole Data 10 –4 • Angular cuts • Track reconstruction 10 –6 quality cut • Advanced cuts: Trigger South Pole Angular cuts Track quality Advanced cuts log likelihood, decision trees, support vector machines Passing rates, 22 strings 11
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 observed flux is consistent with background expectations 12
wimps in the sun • Muon flux limit 2 0.05 < h < 0.20 � probes spin- � -33 -33 10 10 ) 2 Neutralino-proton SD cross-section (cm CDMS (2008) lim � < � CDMS(2008)+XENON10(2007) SI SI COUPP (2008) dependent -34 -34 KIMS (2007) 10 10 SUPER-K 1996-2001 IceCube-22 2007 (soft) neutralino-proton IceCube-22 2007 (hard) -35 -35 10 10 cross-section -36 -36 10 10 Soft • Dependent on -37 -37 10 10 models of dark -38 -38 10 10 Hard matter density -39 -39 10 10 Allowed distribution and mssm -40 -40 10 10 models annihilation modes -41 -41 10 10 2 2 3 3 4 4 10 10 10 10 10 10 10 10 Neutralino mass (GeV) • Hard: W + W – Soft: bb prl 102, 201302 (2009) 13
wimps in the sun 1 ) 2 m • Muon flux limit ( a Preliminary e - 1 r 10 2 A 0.05 < h < 0.20 � probes spin- � -33 -33 o 10 10 ) n 2 Neutralino-proton SD cross-section (cm 80 strings + DeepCore CDMS (2008) lim i � < � CDMS(2008)+XENON10(2007) r SI SI t - 2 COUPP (2008) 10 u dependent e -34 -34 KIMS (2007) N 10 10 SUPER-K 1996-2001 e v IceCube-22 2007 (soft) neutralino-proton i - 3 10 t c IceCube-22 2007 (hard) -35 -35 e 10 10 f f E s g cross-section n - 4 10 i r -36 -36 t 10 10 s 0 8 Soft - 5 10 • Dependent on -37 -37 10 10 models of dark - 6 10 -38 -38 1 1.2 10 10 1.4 Hard 1.6 1.8 2 2.2 2.4 2.6 2.8 log 3 (Primary Neutrino Energy - GeV) matter density 1 0 -39 -39 10 10 Allowed distribution and mssm -40 -40 10 10 models annihilation modes -41 -41 10 10 2 2 3 3 4 4 10 10 10 10 10 10 10 10 Neutralino mass (GeV) • Hard: W + W – Soft: bb prl 102, 201302 (2009) 13
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 14
wimps in the galaxy • Galactic Halo extends below On-source Off-source horizon • Compare equal areas on-source Galactic Center and off-source • Measure flux difference, pick models, and constrain self-annihilation cross-section R ⊙ ρ 2 d Φ dE = 1 dN 2 ⟨ σ A v ⟩ J ( ψ ) ⊙ 4 π m 2 dE χ 15
wimps in the galaxy Limits (90% C.L.) on the self annihilation cross section ( �� -> bb, WW, µµ , �� ) bb NFW halo model IceCube 40 (GC) 10 − 18 IceCube 22 (outer Galaxy) Halo Model Uncertainty unitarity bound bb y r a < σ A v> [cm 3 s − 1 ] 10 − 20 WW n WW i µµ µµ m �� i 10 − 22 l e �� r p 10 − 24 • 90% confidence exclusion limit natural scale 10 − 26 10 2 10 3 10 4 • Width derives from various m � [GeV] density models See arXiv:0912.5183 16
conclusion • Construction ends next year • 40-string analyses are underway • 79 strings in the ice; taking data starting April 1 • 59-string data available soon • 22-string analyses limit spin- • DeepCore boosts wimp dependent cross-sections sensitivity below 100 GeV 17
thank you U. of Alberta RWTH Aachen U. Bonn Vrije U. Brussel EPF Lausanne U. Libre de Bruxelles U. Alabama, Tuscaloosa Chiba U. DESY, Zeuthen U. Alaska, Anchorage U. Dortmund U.C. Berkeley U. Gent Clark-Atlanta U. MPI Heidelberg U. Delaware/Bartol Inst. U. of West Indies Humboldt U., Berlin Georgia Tech U. Mainz U.C. Irvine U. de Mons-Hainaut U. of Kansas Oxford U. Lawrence Berkeley Nat. Lab RuhrU. Bochum U. of Maryland Stockholm U. Ohio State U. Uppsala U. Pennsylvania State U. U. Wuppertal Southern U., Baton Rouge U. of Wisconsin-Madison U. of Wisconsin-River Falls U. of Canterbury, Christchurch The IceCube Collaboration 36 institutions { � 250 physicists
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