Testing Dark Matter with neutrino detectors

1. Testing Dark Matter with neutrino detectors MPI, Heidelberg (Germany) April 14, 2008

2. Evidences of DM Rotation curves of galaxies and clusters Weak modulation of strong lensing, Oort discrepancy, weak gravitational lensing, velocity dispersions of dwarf spheroidal galaxies and of spiral gallaxy satellites… Black-holes, brown dwarfs, white dwarfs, giant planets, neutron stars …? Need non-luminous matter

3. Cosmological evidences Non-baryonic Dark Matter • WMAP Best-fit for a flat ¤CDM model: mh2 = 0.1326 ± 0.0063 But… bh2 = 0.02229 ±0.00073 NASA / WMPA Science Team, WMAP 5-year results B. D. Fields and S. Sarkar, PDG

4. Other evidences S. Cole etal. [2dFGRS Collaboration], Mon.Not.Roy.Astron.Soc.362:505-534,2005 W. L. Freedman et al., [HST Collaboration], Astrophys.J.553:47-72,2001 M. Tegmark et al., [SDSS Collaboration], Phys.Rev.D74:123507,2006

6. Nature of the Dark Matter Standard Model Neutrinos, sterile neutrinos, axions, neutralinos, sneutrinos, gravitinos, axinos, light scalars, from little Higgs models, Kaluza-Klein, super-heavy particles, Q-balls, mirror particles, charged massive particles, self-interacting particles, D-matter, cryptons, superweakly interacting particles, brane world particles, heavy fourth generation neutrinos…

7. What do we know about Dark Matter? Astrophysicist view: Particle Physicist view:

8. Detecting DM Direct Detection Nuclear recoil produced by DM elastic scattering Collider Searches Missing energy Indirect Detection Observation of annihilation products Gamma-ray telescopes (MAGIC, CANGAROO-III, HESS, VERITAS, EGRET, GLAST…)‏ Anti-matter experiments (HEAT, BESS, PAMELA…)‏ Neutrino detectors/telescopes (IceCUBE, ANTARES, AMANDA, Super-Kamiokande…)‏

9. Direct Detection Spin-independent Spin-dependent Z. Ahmed et al. [CDMS Collaboration], arXiv:0802.3530 J. Angle et al. [XENON Collaboration], Phys. Rev. Lett. 100:021303, 2008 D. S. Akerib et al. [CDMS Collaboration], Phys. Rev. D73:011102, 2006 G. J. Alner et al. [UK Dark Matter Collaboration], Phys. Lett. B616:17, 2005

10. Some DM properties • DM may acumulate in celestial bodies like the Sun • DM-nucleon elastic cross section sets the normalization • Different annihilation channels imply different º flux • How big is the annihilation cross section? • For a thermal relic: <σv> ~ 3 x 10-26 cm3/s • But…DM might only exist in the late Universe • <σv> sets the rate of DM annihilation in DM halos • If DM is unstable, how long does it live? • τ would set the rate of DM decay in DM halos Can we test them with neutrino detectors?

11. Annihilations from the Sun

12. Indirect Neutrino Detection • WIMPs elastically scatter with the nuclei of celestial bodies to a velocity smaller than the escape velocity, so they remain trapped inside • Additional scatterings give rise to an isothermal distribution • Trapped WIMPs can annihilate into SM particles • After some time, annihilation and capture rates equilibrate • Only neutrinos can escape

13. Famous WIMPs • SUSY WIMPs (LSP): Neutralinos, Sneutrinos, Gravitinos, Axinos • Neutralinos: Majorana particles • Annihilations proportional to mf • Kaluza-Klein WIMPs (LKP): B(1) • No chirality suppression • Annihilation: 35% quarks, 60% charged leptons

14. Neutrinos from WIMP annihilations Distance source-detector Neutrino spectrum from annihilation channel i Branching ratio into annihilation channel i

15. Neutrino spectra at production M. Cirelli et al., Nucl. Phys. B727:99, 2005

16. Neutrino spectra at detection Need to take into account oscillations and solar absorption M. Cirelli et al., Nucl. Phys. B727:99, 2005

17. IceCube, ANTARES… Detection of muon events induced by muon neutrinos Counting experiments above some energy threshold

18. Limits from SK Spin-independent Spin-dependent S. Desai et al., Phys. Rev. D70:083523, 2004

19. Rates in a Neutrino Telescope F. Halzen and D. Hooper, Phys. Rev. D73:123507, 2006 To get the same rate: trade annihilation channel by cross section

20. Future Neutrino Detectors Magnetized Iron Calorimeters MINOS-like, INO… Totally Active Scintillator Detectors NOvA, MINERvA… Liquid Argon Time Projection Chamber GLACIER… Very good angular and energy resolution for ºe and/or º¹ for 10’s of GeV → suitable for low mass WIMPs “Small” detectors: only suitable for neutrinos from annihilations in the Sun

21. Angular and Energy Resolutions for MIND • We take 5 GeV-energy bins • We take the rms spread in the direction between the neutrino and the lepton: T. Abe et al., The ISS Detector Working Group

22. Neutrino Events º¹-events ºe-events Determination of WIMP mass

23. mDM = 50 GeV BR¿+¿- = 0.20 mDM = 70 GeV BR¿+¿- = 0.10 O. Mena, SPR and S. Pascoli, arXiv:0706.3909 to be published in Phys. Lett. B

24. Annihilations from the halo

25. Model-independent bound • Neutrinos are the least detectable particles of the SM • From the detection point of view the most conservative assumption (the worst case) is that DM annihilates only into º’s: ÂÂ→ ºº • This is not an assumption about realistic models • It provides a bound on the total annihilation cross section and not on the partial cross section to neutrinos • Anything else would produce photons, and hence would lead to a stronger limit

26. Strategy • Calculate neutrino flux: proportional to annihilation cross section and ½DM2 • For E ~ 100 MeV – 100 TeV the main background: atmospheric neutrino flux • Consider angle-averaged flux in wide energy bins • Compare potential signal with the well known and measured background: set upper bound on the DM annihilation cross section

27. Signal Experiment Particle Physics Astrophysics

28. Field of View Neutrino Spectrum: Flavor democracy Average of the Line of Sight Integration of ½2

29. Dark Matter Profiles Moore et al. NFW Kravstov et al.

30. Uncertainties SPR and S. Pascoli, Phys. Rev. D 77, 025025 (2008) • From the allowed range of: • Local rotational velocity • Amount of flatness • Non-halo components P. Belli et al., Phys.Rev.D66:043503, 2002

31. Compare against atmospheric neutrino background M. Honda et al., Phys.Rev.D75:043006,2007

32. Energy resolution: ¢log E = 0.3 H. Yüksel, S. Horiuchi, J. F. Beacom and S. Ando , Phys. Rev. D76:123506, 2007

33. Can we do better? Careful treatment of energy resolution and backgrounds: eg. limits on MeV DM We use SK data for E = 18-82 MeV Detection: ºe + p → e+ + n Two main backgrounds: Invisible muons Atmospheric neutrinos M. S. Malek, Ph.D thesis M. S. Malek et al., Phys. Rev. Lett. 90:061101, 2003

34. Analysis 16 4-MeV bins in the range [18,82] MeV Nl = Number of events in bin l Al = fraction of signal events Bl = fraction of Michel electrons (positrons) Cl = fraction of atmospheric electron (anti)neutrinos

35. We perform a similar Â2 analysis as that done by SK to limit the flux of DSNB and we set an upper bound on the DM annihilation cross section SPR and S. Pascoli, Phys. Rev. D 77, 025025 (2008)

36. What if this is actually the case and DM only annihilates into neutrinos? C. Boehm, Y. Farzan, T. Hambye, SPR and S. Pascoli, Phys. Rev. D 77, 043516 (2008) LENA: 50000 m3 scintillator after 10 years Reactor BG DSNB Atmospheric BG SPR and S. Pascoli, Phys. Rev. D 77, 025025 (2008)

37. Decays from the halo

38. Neutrinos are the least detectable particles of the SM From the detection point of view the most conservative assumption is that DM decays only into º’s :  → ºº Flux proportional to the inverse of the DM lifetime and ½DM For E ~ 100 MeV – 100 TeV the main background: atmospheric neutrino flux Compare potential signal with the well known and measured background: set lower bound on the DM lifetime

39. Signal Experiment Particle Physics Astrophysics

40. Field of View Neutrino Spectrum: Flavor democracy Average of the Line of Sight Integration of ½

41. Using SK data from DSNB search: Detailed analysis of background and energy resolution New model-independent bound from CMB and SN observations Model-independent bound from CMB observations SPR, arXiv:0712.1937 Y. Gong and X. Chen, arXiv:0802.2296 K. Ichiki, M. Oguri and K. Takahashi, Phys. Rev. Lett. 93, 071302 (2004)

42. Conclusions Neutrino detectors can test DM properties Searches for neutrinos from DM annihilations/decays in celestial bodies could constitute powerful probes of DM properties Cherenkov neutrino detectors/telescopes are counting experiments and could only provide limited information Future neutrino detectors (MIND, TASD and LArTPC) will have very good energy resolution for 10’s GeV Reconstructing the neutrino spectra → information on DM mass, annihilation branching ratios and DM-proton cross section Due to small size, only suitable for large spin-dependent cross sections and neutrinos from annihilations in the Sun, but complementary to Neutrino Telescopes (with higher threshold)‏ Neutrino detectors can set model-independent bounds on the DM annihilation cross section and on the DM lifetime Future detectors (LENA) might be able to detect a signal from DM annihilations/decay

43. The world is full of obvious things which nobody by any chance ever observes When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth. Sherlock Holmes