Sergio Palomares-Ruiz June 4, 2008 Testing Dark Matter with neutrino detectors Melbourne Neutrino Theory Workshop Melbourne (Australia) June 2-4, 2008

Sergio Palomares-Ruiz June 4, 2008 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… Need non-luminous matter Black-holes, brown dwarfs, white dwarfs, giant planets, neutron stars …?

Sergio Palomares-Ruiz June 4, 2008 Cosmological evidences WMAP Best-fit for a flat ¤CDM model:  m h 2 = ± But…  b h 2 = ± Non-baryonic Dark Matter B. D. Fields and S. Sarkar, PDG NASA / WMPA Science Team, WMAP 5-year results

Sergio Palomares-Ruiz June 4, 2008 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…

Sergio Palomares-Ruiz June 4, 2008 What do we know about Dark Matter? Astrophysicist view: Particle Physicist view:

Sergio Palomares-Ruiz June 4, 2008 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…) ‏

Sergio Palomares-Ruiz June 4, 2008 Direct Detection D. S. Akerib et al. [CDMS Collaboration], Phys. Rev. D73:011102, 2006 G. Angloher et al. [CRESST Collaboration], Astropart. Phys. 23:325, 2005 Spin-independent Spin-dependent Z. Ahmed et al. [CDMS Collaboration], arXiv: J. Angle et al. [XENON Collaboration], Phys. Rev. Lett. 100:021303, 2008 H. S. Lee et al. [KIMS Collaboration], Phys. Rev. Lett. 99:091301, 2007 E. Behnke et al. [COUPP Collaboration], Science 319:933, 2008

Sergio Palomares-Ruiz June 4, 2008 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 ν flux How big is the annihilation cross section? For a thermal relic: ~ 3 x cm 3 /s But…DM might only exist in the late Universe 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?

Sergio Palomares-Ruiz June 4, 2008

Sergio Palomares-Ruiz June 4, 2008 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

Sergio Palomares-Ruiz June 4, 2008 Neutrinos from WIMP annihilations Distance source-detector Branching ratio into annihilation channel i Neutrino spectrum from annihilation channel i

Sergio Palomares-Ruiz June 4, 2008 Neutrino spectra at detection Need to take into account oscillations and solar absorption M. Cirelli et al., Nucl. Phys. B727:99, 2005

Sergio Palomares-Ruiz June 4, 2008 IceCube, ANTARES… Counting experiments above some energy threshold Detection of muon events induced by muon neutrinos

Sergio Palomares-Ruiz June 4, 2008 Limits from SK S. Desai et al., Phys. Rev. D70:083523, 2004 Spin-independentSpin-dependent

Sergio Palomares-Ruiz June 4, 2008 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

Sergio Palomares-Ruiz June 4, 2008 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 ν e and/or ν ¹ for 10’s of GeV → suitable for low mass WIMPs “Small” detectors: only suitable for neutrinos from annihilations in the Sun

Sergio Palomares-Ruiz June 4, 2008 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

Sergio Palomares-Ruiz June 4, 2008 Neutrino Events ν ¹ -events ν e -events Determination of WIMP mass

Sergio Palomares-Ruiz June 4, 2008 O. Mena, SPR and S. Pascoli, Phys. Lett. B664:92, 2008 m DM = 50 GeV BR ¿ + ¿ - (hard) = 20% m DM = 70 GeV BR ¿ + ¿ - (hard) = 10%

Sergio Palomares-Ruiz June 4, 2008

Sergio Palomares-Ruiz June 4, 2008 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 ν’s: Â Â → νν 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 J. F. Beacom, N. F. Bell and G. D. Mack, Phys. Rev. Lett. 99:231301, 2007

Sergio Palomares-Ruiz June 4, 2008 Strategy Calculate neutrino flux: proportional to annihilation cross section and ½ DM 2 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

Sergio Palomares-Ruiz June 4, 2008 Signal Experiment Particle PhysicsAstrophysics

Sergio Palomares-Ruiz June 4, 2008 Field of View Neutrino Spectrum: Flavor democracy Average of the Line of Sight Integration of ½ 2

Sergio Palomares-Ruiz June 4, 2008 Energy resolution: ¢ log E = 0.3 H. Yüksel, S. Horiuchi, J. F. Beacom and S. Ando, Phys. Rev. D76:123506, 2007 Other related limits M. Kachelriess and P. D. Serpico, Phys. Rev. D76:063516, 2007 N. F. Bell, J. B. Dent, T. D. Jacques and T. J. Weiler, arXiv: J. B. Dent, R. J. Scherrer and T. J. Weiler, arXiv: G. D. Mack, T. D. Jacques, J. F. Beacom, N. F. Bell and H. Yüksel, arXiv:

Sergio Palomares-Ruiz June 4, 2008 Can we do better? Careful treatment of energy resolution and backgrounds: eg. limits on MeV DM We use SK data for E = MeV Detection: ν e + 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

Sergio Palomares-Ruiz June 4, 2008 We perform a similar  2 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. D77, (2008)SPR, arXiv:

Sergio Palomares-Ruiz June 4, 2008 LENA: m 3 scintillator after 10 years Reactor BGDSNBAtmospheric BG SPR and S. Pascoli, Phys. Rev. D77, (2008) 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, (2008)

Sergio Palomares-Ruiz June 4, 2008

Sergio Palomares-Ruiz June 4, 2008 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 ν’s : χ → νν Flux proportional to the inverse of the DM lifetime and ρ DM 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

Sergio Palomares-Ruiz June 4, 2008 Signal Experiment Particle PhysicsAstrophysics

Sergio Palomares-Ruiz June 4, 2008 Field of View Neutrino Spectrum: Flavor democracy Average of the Line of Sight Integration of ρ

Sergio Palomares-Ruiz June 4, 2008 SPR, arXiv: to be published in Phys. Lett. B Model-independent bound from CMB observations K. Ichiki, M. Oguri and K. Takahashi, Phys. Rev. Lett. 93, (2004) Using SK data from DSNB search: Detailed analysis of background and energy resolution New model-independent bound from CMB and SN observations Y. Gong and X. Chen, arXiv:

Sergio Palomares-Ruiz June 4, 2008 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

Sergio Palomares-Ruiz June 4, 2008 When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth Sherlock Holmes The world is full of obvious things which nobody by any chance ever observes