Search for Dark Matter particles with Super-Kamiokande detector
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Search for Dark Matter particles with Super-Kamiokande detector

Seminarium Doktoranckie IPJ, 17.VI.2008, WarszawaSearch for Dark Matter particles withSuper-Kamiokande detectorPiotr MijakowskiInstytut Problemów Jądrowych, Warszawska Grupa Neutrinowa

OUTLINE» Dark Matter• evidences, candidates• current experimental status» Indirect search for Dark Matter• gamma• antimatter• neutrinos» Search for WIMPs with Super-Kamiokande:• directional neutrino flux (Sun, Earth, Galaxy Center)• diffuse neutrino flux» SummaryP.Mijakowski 17.06.2008, Warszawa 2

Dark Matter in the UniverseUniverse – dominant mass contribution from unknown mattercomponent. It manifests only through gravitational interaction withsurrounding baryonic matter. Its presence determinesevolution of Universe and can be derived from:» Velocity distribution in galaxy clusters(F.Zwicky in 1933)» Galaxies rotation curves» Gravitational lensing» Cosmic Microwave Backround (CMB)1E0657-558» Abundance of light elements in Universe,nucleosynthezis» Evolution of large cosmic structures

ΛCDM model» ΛCDM – cosmological model based on recent observations: CMB,large scale structures, accelerating expansion of Universe» Ω Ω tot = 1.02 ± 0.02 „flat” Universe!Cosmological parameterstot» Ω mcosmic microwave background (WMAP - 2003 r.)Ω m = 0.27 ± 0.02WMAP (2006 r.)Ω m ~ 0.3gravitational interactions (i.e. rotation curves)» Ω b Ω b ~ 0.040 ± 0.005Big Bang Nucleosynthezis (BBN) + abundance of ligh elements (H,D,He,Li)Ω b ~ 0.044 ± 0.002 » Ω lumniΩ lumni ~ 0.006WMAP (2006 r.)Luminescence of stars and interstellarmediumP.Mijakowski 17.06.2008, Warszawa 4

ΛCDM modelCosmological parameters» Ω Λ Ω Λ= 0.73 ± 0.02WMAP (2006 r.) + SN IaConclusions:Ω m >> Ω b => Dark MatterΩ m < 1 => Dark EnergyP.Mijakowski 17.06.2008, Warszawa 5

Dark Matter - candidates» Existing particles• MACHO’s (Massive Astronomical Compact Halo Objects), i.e. browdwarfves, neutron stars, black holes• neutrinos - Hot Dark Matter (HDM)< 7% Galactic Halo mass (exp. EROS)cosmic structure» Predicted:formation requires CDM• Axions• WIMPs (Weakly Interacting Massive Particles) - Cold Dark Matter(CDM)» Exotic:• WIMPzillas, LIMPs, Kaluza-Klein DM, monopoles, sterile neutrinos…P.Mijakowski 17.06.2008, Warszawa 6

neutralWIMPWeakly Interacting Massive Particle long lived(with τ ~ age of Universe) massive ( M χ ~ 100 GeV) weakly scale couplingsσ ≤ 10 -2 pb (10 -38 cm 2 )well motivated WIMP candidate:Search for particles: neutralino χ (SUSY) - Lightest Supersymmetric Particle (LSP), stable (R-parityconservation in SUSY)neutralino(χ)neutralino couplings (example):Jungman, Kamionkowski, Griest, Phys. Rep., 267, 195 (1996)18 GeV < M χ < 7 TeVLEPcosmologyP.Mijakowski 17.06.2008, Warszawa 7

Search for WIMPs»Direct detection experiments• WIMP-nucleuos elastic scatteringmeas. on Earth, χ from Galactic Haloenergy meas. -> ionization,scintillation, phonons, ∆T• production in accelerators (LHC)»Indirect detection experiments• search for products of Dark Matter annihilation– neutrinos– antimatter– gammasP.Mijakowski 17.06.2008, Warszawa 8

Direct detection – current experimental limitsWARP(2.3 l. Ar)DAMA NaI,90% CL regionZeplin II (Xe)» Region abovelines is excludedwith 3σ CL» DAMA 1.1x10 5 kgd(7 lat, 100 kg NaI)» Hidden assumptions:• interaction (spindependance)• Galactic Halo ModelEdelweiss (Ge)CDMS II, 2004-05 (Ge)(34 kg·d)CDMS II, 2007predictionXENON (10kg)2007, 136 kg·dP.Mijakowski 17.06.2008, Warszawa 9

Indirect search for a DM particles» Indirect search = search for annihilation productsof χ’s (self-antiparticle):• gammas (HESS, MAGIC, WHIPPLE, CANGAROO-II, EGRET, GLAST)• anti-matter: positrons, anti-deuteron, anti-proton(HEAT, BESS, PAMELA, AMS-02 … )• neutrinos (Super-Kamiokande, Ice-Cube, ANTARES)χχ →qq( cc,bb,tt ,...)W±ll, Z,H→.....→ν, γ , e,p,H2,P.Mijakowski 17.06.2008, Warszawa 10

DM self-annihilation cross section- cross section averaged over the relative velocity distribution„freeze out” of the relic particle» Sets the obs. DM mass densityΩ Μ = 0.27 ± 0.02 WMAP (2006 r.)-> in thermal relic scenarios:~ 3 x 10 -26 cm 3 /s» Sets the annihilation rate in DM halos2- DM number densityP.Mijakowski 17.06.2008, Warszawa 11

AdvantagesDM annihilation to gammas» insensitive to magnetic fields(source information)» not attenuated over galacticscales – energy spectrum» produced in the most of WIMPannihilation modes, π 0 decays(abundant ann. product)Uncertainities:» Astrophysical background rate• distribution around GalacticCenterP.Mijakowski 17.06.2008, Warszawa 12

DM annihilation to gammas - EGRET» EGRET excess in diffuse galactic gamma ray flux50-100 GeV neutralino annihilation?P.Mijakowski 17.06.2008, Warszawa 13

DM annihilation to gammas - EGRETObjections to EGRET interpretation» DM density concentrated to thegalactic plane. This is not what oneexpects from CDM!» Excess in anti-protons data – NOTobserved (correlation: fragmentationof quark jets)» Instrumental problem with EGRET?» Too simple conventional model for galacticgamma-ray emission?await GLASTP.Mijakowski 17.06.2008, Warszawa 14

DM annihilation to positrons (HEAT)(*) D. Hooper., Annu. Rev. Nucl. Part. Sci. (2008), Vol. 58» for• DATA:HEAT exp.• solid line:Galactic cosmicray model(Moskalenko &Strong)• Dotted lines –WIMP masses100, 300,600GeV−26 33» for σAv = 3×10 cm / s , ρ = 0 .3 GeV / cmχann. rate should be boosted ~50to normalize the HEAT data» Consequence: DM clumps in local halo (but expected only ~5-10);different cross section (then should be observed by others)

DM annihilation to neutrinos… where they may come from?Search for neutrinosfrom DM annihilation (approaches)Directional fluxrelated to regions of increased DMdensity:• core of Sun, Earth, GalaxyCenter• constrain SD/SI σ χnDiffuse flux:• flux averaged over large cosmicvolumes (many galactic halos)• flux averaged only over Milky Way• constrain DM self-annihilation crosssection

WIMP capture and annihilationρ χχSUNEarthσ scattΓ captureΓ annihilationν int. µ int.ν µdetectorχ scattering in the Sunχ annihilationχZµνP.Mijakowski 17.06.2008, Warszawa 17χν

Super-KamiokandeWater Cerenkov detectorin Kamioka, Japan• 50kton water, , 22.5ktonfiducial volume• 12k inner PMTs /2kouter PMTsdetect light; possiblereconstruction of energyand direction ofneutrinos• SK investigatesatmopsheric/cosmiccosmic,solar & accelerator ν• detect SN1987 ν’s• neutrino oscilationdiscovery (1998)P.Mijakowski 17.06.2008, Warszawa 18

Water Cerenkov detector principle» Charged particles propagating in water with v > c in water emit e-m radiationHow to observe neutrino?» Charged Current» Neutral Current» Elastic Scatteringν x + N->µ/τ/e+p+…ν x + N->ν+n+…ν x + e - ->ν+e -P.Mijakowski 17.06.2008, Warszawa 19

Super-KamiokandeCerenkov ring categories: » e-like (e, π0 )» µ-like (µ, π+, π-, kaons…)source: Science@berkeley lab, 30 January 2006

Neutrino events in Super-KamiokandeMonte Carlo

Search for WIMPs in SuperK (directional flux)EARTHSUN(*) S.Desai et al., Phys.Rev. D70 (2004) 083523» Search for an excess of neutrinos in SK1 data» WIMP mass range 18GeV-10TeV -> neutrino energy: ~5 GeV – 5 TeV» Data sample: upward through-going muons» Currently new analysis: more data, lower energy neutrinos also included(T.Tanaka, officialize soon)

SuperK – WIMP-induced neutrino fluxlimit from EarthLimit: WIMP-induced upward muons (EARTH)simulationhalf-angle of cone which contains90% of neutrino flux form WIMPannihilation in Earth(*) S.Desai et al., Phys.Rev. D70 (2004) 083523P.Mijakowski 17.06.2008, Warszawa 27

SuperK – WIMP-induced neutrino fluxlimit from SunLimit: WIMP-induced upward muons (SUN)simulationhalf-angle of cone which contains90% of neutrino flux form WIMPannihilation in Sun(*) S.Desai et al., Phys.Rev. D70 (2004) 083523P.Mijakowski 17.06.2008, Warszawa 28

SuperK limit for neutralino elastic crosssection (spin independent)» Comparison with direct detection:model dependent, assuming onlyspin-independent interactions inEarth and Sun & equilibrium (equalannihilation and capture rate)» Direct and Indirect event rates:Evt. rate in 1 kg Ge detector =Evt. Rate in 10 4 -10 6 m 2 of upwardmuon detector (assuming SIcouplings)comparison with direct detection» Currently: lowest limit in direct detection -> XENON, ~10 -7 pb (10 -43 cm 2 ) for a100 GeV WIMP(*) S.Desai et al., Phys.Rev. D70 (2004) 083523

SuperK limit for neutrialino elasticcross section (spin dependent)(*) S.Desai et al., Phys.Rev. D70 (2004) 083523; Erratum-ibid. D70 (2004) 109901(*) Kamionkowski, Ullio, Vogel JHEP 0107 (2001) 044» Limit 100 times lower than from direct search experiments» DAMA annual modulation due to axial vector couplings ruled out bythis result (Kamionkowski et al.)

DM annihilation to neutrinos (diffuse flux)» DM ann. BR to specific finalstates are model dependent(also ν energy spectra)» „Golden channel” signature:(*) J.F.Beacom et al., Phys. Rev. D76, 123506 (2007)monoenergetic neutrinosneutrino energy = WIMP mass» PLOT (illustration):• Atm. neutrino spectrum (ν µ ,ν µ )• + signal from annih. of 100GeV WIMP• MW – Milky Way contribution• COSMIC – diffuse fluxaveraged over large cosmicvolumes -> energy smearingdue to different red-shifts ofsourcesP.Mijakowski 17.06.2008, Warszawa 31

DM annihilation to neutrinos (diffuse flux)Beacom et al. analysis:» SIGNAL = monoenergetic neutrinosfrom DM annihilation» BKG = ATM. Neutrinos» atm. neutrino data from SuperK,AMANDA, Frejus» Consider wide neutrino energy bins» Compare integrated: SIGNAL MC withDATA for same bin» Require that signal be 100% as large asatm. BKG in same bin (conservative)(*) J.F.Beacom, N.F.Bell, G.D.Mack, Phys. Rev. Lett. 99 (2007) 231301MC atm. neutrino spectrum + signalfrom DM ann.Ratio: total / atm.background

Upper bound on DM total annihilationcross section» No upward fluctuations in available data» Limit on DM-induced neutino diffuse fluxand DM annihilation cross section(constrains on DM evolution anddistribution)» combining with γ searches -> provideconservative upper limit on total Assumption: BR = 100% forConsequence:General upper limit on the total DM self annihilation cross section. Why?Least detectable particles bounds total cross section most conservatively -> all other limits(derived from other ann. products, like γ’s) would be more stringent than that; limit on crosssection derived that way cannot be overreached (with only SM final states)

SuperK dedicated analysisDedicated SK/AMANDA analysis could improve limit ontotal self-annihilation cross section by 1-2 orders of magn.(*) J.F.Beacom, N.F.Bell, G.D.Mack, Phys. Rev. Lett. 99 (2007) 231301 :„ … could thus become close to the natural scale for thermal relics,making it a complementary tool for testing even standard scenarios,especially at high energies, where diffuse gamma rays areattenuated.”Why?use special features of SK data like…P.Mijakowski 17.06.2008, Warszawa 34

SuperK data (energy)» Look for DM annihilation singal (upward fluctuations)/limit in data:FC: fully containedPC: partially containedUPMU: upward going muonsFC e-like٠ DATA__ ATM MCFC µ-like٠ DATA__ ATM MCMulti RingFC µ٠ DATA__ ATM MC+ + UPMUs+PC µ٠ DATA__ ATM MCshoweringUPMUsWhat can be improved comparing to Beacom analysis?» Use narrower bining & realistic data uncertainities» Advantage of SuperK precise low energy data -> strong limit» High statistics of upward & upward showering muons… next slide(*) Y. Ashie et al., Phys. Rev. D 71, 112005 (2005)

SuperK data (cosθ,flavor)ExampleWhat can be improved comparing to Beacom analysis?» use angular feature:WIMP diffuseDM signal isotropic, atm. neutrino bkgis often peaked at horizon» use (ν e , ν e ):• same ν e ,ν ,ν τ µratio is assumed in• use atm. (ν e, ν e) data ( (ν τ,ν τ)enriched sample?)higher signal to BKG ratio than in (ν µ,ν µ)stronger limitP.Mijakowski 17.06.2008, Warszawa 36

SK diffuse flux method summaryMETHOD (proposed by P.Mijakowski):FC: fully containedPC: partially containedUPMU: upward going muons» Use (ν e , ν e ), (ν µ, ν µ )» Investigate energy (FC, PC) & cosθ (UPMU, FC, PC)distributions» Simulate DM annihilation diffuse signal» Test the DM annihilation singal hypothesis in atm databy minimazing χ 2 distributions:2χ=nbins∑i=1(obs(atmνWIMPN − α ⋅ N + β ⋅ N)iiσii2For every WIMP mass» Derive limits on self-annihilation cross sectionP.Mijakowski 17.06.2008, Warszawa 37

SUMMARY» DARK MATTER – mystery to be solved soon ? … many direct &indirect search experiments, production in LHC» Indirect search – excess gamma/antiproton fluxes in fewexperiments to be verified soon by next generation experiments» No excess in neutrino flux from center of Earth/Sun/Galaxy inSuper-Kamiokande data -> limit on SI/SD σ χn» Search for neutrino diffuse flux form DM annihilation inSuper-Kamiokande would be first dedicated analysis and result inworldP.Mijakowski 17.06.2008, Warszawa 38



(*) D. Hooper., Annu. Rev. Nucl. Part. Sci. (2008), Vol. 58» WIMP’s effectiveelastic scatteringcross section in theSun for a variety ofannihilation modes.The effective elasticscattering crosssection is defined asσeff =σH,SD+σH,SI+0.07σHe,SIThe dashes, solid anddotted linescorrespond to WIMPsof mass 100, 300 and1000 GeV, mnie» „To detect neutrinos from WIMP annihilations in the Sun overthe background of atmospheric neutrinos, a rate in the range of10-100 events per square-kilometer, per year is required”P.Mijakowski 17.06.2008, Warszawa 41

SuperK dedicated analysisDedicated SK/AMANDA analysis could improve existing limit on total selfannihilationcross section by 1-2 orders of magn. (*)Beacom» fewer assumptions -> DM distribution in Galatic Center, local haloprofile (clumps?)» conservative upper boundproduction in» assume same ν e ,ν ,ν τ µ» Why?• narrower bining & more realistic data uncertainities• SuperK precise low energy data (

Atmospheric neurinos in SKAtm. ν µ (MC)expected number of neutrino events ineach event category as a function of neutrino energy

DM annihilation to anti-matter» Charged anti-particles (positrons, anti-protons,anti-deuterons)-> diffuse spectrum at Earth» positrons -> lose energy over typical length scales(few kpc), probe the local DM distribution, lessuncertainty» Satellite-based exp.-> HEAT, AMS-01, Pamela, AMS-02 (planned)…P.Mijakowski 17.06.2008, Warszawa 46

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