Indirect searches for dark matter particles with the Super-Kamiokande detector

Transcription

1 Les Rencontres de Physique de la Vallée d'aoste, 1-7 III 2015 Indirect searches for dark matter particles with the Super-Kamiokande detector Katarzyna Frankiewicz National Center For Nuclear Research

2 Indirect dark matter detection - Search for the products of WIMP annihilation or decay Super-Kamiokande Water Cherenkov detector tons of water 1 km underground PMTs 40m 40m Kamioka Observatory, Japan Detector measures solar, atmospheric, cosmic and accelerator 2 neutrinos 2

3 Super-Kamiokande collaboration ~60% ~25% ~6% ~3% ~5% <1% <1% 3 3

4 Kamioka Observatory, ICRR, Univ, of Tokyo 4

5 Detected Cherenkov light allow to reconstruct energy, direction and flavour of neutrino 5 5

6 Neutrinos at Super-Kamiokande Neutrino sources = ~10 /day Main backgound for DM searches: Atmospheric neutrinos 6 6

7 Dark Matter halo models Dark Matter density Expected DM intensity Solar System position Local DM density Expected local DM flux NFW Moore Kravtsov NFW benchmark model Moore & Kravtsov extreme cases (to estimate the impact of halo model choice on the results) 7

8 Expectations: Analysis idea Search for a large-scale anisotropy due to DM-induced ν's from Milky Way on-source N bkg on +N sig on off-source N GC sig on sig off bkg off +N sig off sig Δ N N N =Δ N σ A v Analysis uses on-soufce/off-source method to estimate the background directly from the data - method independent of MC simulations and related systematic uncertainties DM simulation is used only to optimize analysis 8

9 Analysis results: DM annihilation 9

10 Main result: Upper limits on allowed number of DM-induced events Based on SK 1-4 data ( ) νν bb, W+W_, μ+ μ- Sample FC Sub GeV FC Multi GeV PC UPMU ALL Size On-source Off-source Δ N sig ± ± ± ± ± % CL ΔN sig No excess of events has been observed! 10

11 Based on SK 1-4 data: ΔNsig DarkSUSY: Example for bb: Φ No excess of events has been observed! FOR ANNIHILATION: νν, bb, W+W_, μ+μchannels considered DM halo profiles Futher interpretation: For assumed mχ we can calculate <σaν> The same procedure for DM decay analysis 11

12 90% CL upper limits on <σav> + halo model choice influence Regions above lines are excluded 100% BR to a given annihilation mode assumed NFW our benchmark model (lines with markers) Moore (lower) & Kravtsov (upper) extreme cases (bands) 12

13 90% CL upper limits on <σav> - comparison with other results for μ+μ- 100% BR to μ+μannihilation mode assumed IceCube 40: R.Abbasi et al., arxiv: v3 (2013) IceCube multipole: M.G.Aartsen et al., arxiv: (2014) AMS02 best fit: J.Kopp, Phys.Rev.D 88, (2013) PAMELA+FERMI: P.Meade et al., arxiv: v2 (2010) 13

14 Analysis results: DM decay 14

15 Upper limits on allowed number of DM-induced events Based on SK 1-4 data ( ) νν bb, W+W_, μ+μ- Sample FC Sub GeV FC Multi GeV PC UPMU ALL Size On-source Off-source ΔN sig -48± ± ± ± ± % CL ΔN sig Expected WIMP signal shape for NFW profile: Decay intensity ~ ρ Annihilation intensity ~ ρ2 15

16 90% CL lower limits on τ 100% BR to a given decay mode assumed No need to consider three halo models the same expected signal intensity Decay JΔΩ NFW Moore Kravtsov 2,0 2,0 2,1 IceCube 40: R.Abbasi et al., arxiv: v3 (2013) 16

17 Summary Dark Matter search is highly challenging field, the existing results are not conclusive, multi-messenger approach is very important My analysis: Limits on WIMP induced neutrinos based on difference in number of events between on-source and off-source regions: - background is estimated directly from the data The optimal conditions (size of on-source region) for analysis are determined based on performed DM simulation - SK 1-4 data samples are used - Main result is model independent - Four annihilation/decay channels are investigated: χχ νν, bb, W+W_, μ+μ- NFW, Moore and Kravtsov DM halo models are considered 17

18 Kamioka Observatory, ICRR, Univ, of Tokyo 18

19 Piotr Mijakowski 19

20 Piotr Mijakowski 20

21 Equatorial coordinate system Declination (DEC) angular distance of an object perpendicular to the celestial equator Right ascension (RA) angular distance of an object eastward along the celestial equator from the vernal equinox to the hour circle passing through the object Cestial equator GC Image of the sky in equatorial coordinate system This coordinate system does not rotate with the Earth, but remains fixed 21 against the background stars

22 Determination of the optimal size of the on-source region For NFW Profile : Optimization of the S/ B ratio as a function of the distance from the GC angular distance from GC Angular resolution differs between various Event classes FC MultiGeV FC SubGeV Difference between true and reconstructed angular distance from GC [ ] UPMU PC [ ] ALL 22 [ ] [ ] [ ]