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: mh2 = 0.1326 ± 0.0063
But… bh2 = 0.02229 ± 0.00073
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:0802.3530
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: <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?
Sergio Palomares-Ruiz
June 4, 2008
Sergio Palomares-Ruiz
June 4, 2008Indirect 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
2
2
3
3124 GeV 50
pb 10km/s 270
GeV/cm 3.0109
DMlocal
local
mvsC
eq
ann ttC 2tanh
21
Sergio Palomares-Ruiz
June 4, 2008Neutrinos from WIMP
annihilations
i
ii
ann
dEdNBR
RdtdEddN
24
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-independent Spin-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 νe and/or ν¹ 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, 2008Angular 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:
EGeV
rms ~
T. Abe et al., The ISS Detector Working Group
Sergio Palomares-Ruiz
June 4, 2008 Neutrino Eventsν¹-events νe-events
Determination of WIMP mass
Sergio Palomares-Ruiz
June 4, 2008
O. Mena, SPR and S. Pascoli, Phys. Lett. B664:92, 2008
mDM = 50 GeVBR¿+¿- (hard) = 20%
mDM = 70 GeVBR¿+¿-(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 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
Sergio Palomares-Ruiz
June 4, 2008 Signal
annsc JR
dEdN
mdEd
2
02 2
4
Experiment Particle Physics Astrophysics
Sergio Palomares-Ruiz
June 4, 2008 Field of View
Neutrino Spectrum: Flavor democracy
Average of the Line of Sight Integration of ½2
cos12
mEdEdN
32
cos 2)(11 1
cos 0
220
max ddrR
Jsc
ann
22 cos2 scsc RRr cossin 222max scschalo RRR
Sergio Palomares-Ruiz
June 4, 2008
Energy resolution: ¢log E = 0.34
GeV 10 GeV 1030 E
Eo
GeV 10 30 Eo
H. Yüksel, S. Horiuchi, J. F. Beacom and S. Ando, Phys. Rev. D76:123506, 2007
Other related limitsM. Kachelriess and P. D. Serpico, Phys. Rev. D76:063516, 2007N. F. Bell, J. B. Dent, T. D. Jacques and T. J. Weiler, arXiv:0805.3423J. B. Dent, R. J. Scherrer and T. J. Weiler, arXiv:0806.0370G. D. Mack, T. D. Jacques, J. F. Beacom, N. F. Bell and H. Yüksel, arXiv:0803.0157
Sergio Palomares-Ruiz
June 4, 2008Can 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: νe + p → e+ + n• Two main backgrounds:
– Invisible muons– Atmospheric neutrinos
M. S. Malek, Ph.D thesisM. S. Malek et al., Phys. Rev. Lett. 90:061101, 2003
Sergio Palomares-Ruiz
June 4, 2008
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. D77, 025025 (2008)SPR, arXiv:0805.3367
Sergio Palomares-Ruiz
June 4, 2008
LENA: 50000 m3 scintillator after 10 years
Reactor BG DSNB Atmospheric BGSPR and S. Pascoli, Phys. Rev. D77, 025025 (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, 043516 (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 ρDM
• 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
dksc JR
dEdN
mdEd
0 1 4
Experiment Particle Physics Astrophysics
Sergio Palomares-Ruiz
June 4, 2008 Field of View
Neutrino Spectrum: Flavor democracy
Average of the Line of Sight Integration of ρ
cos12
2/32
mEdEdN
cos 2)(11 1
cos 00
max ddrR
Jsc
dk
22 cos2 scsc RRr
cossin 222max scschalo RRR
/
/1/1)(
s
sscscsc rr
rRrRr
Sergio Palomares-Ruiz
June 4, 2008
SPR, arXiv:0712.1937to be published in Phys. Lett. B
Model-independent boundfrom CMB observations
K. Ichiki, M. Oguri and K. Takahashi,Phys. Rev. Lett. 93, 071302 (2004)
GeV 10 GeV 1030 EE
o
GeV 10 30 Eo
4
Using SK data from DSNB search:Detailed analysis of background and energy resolution
New model-independent boundfrom CMB and SN observations
Y. Gong and X. Chen, arXiv:0802.2296
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