1. The Status of DAMA and Direct Detection of WIMPs Limits from DAMA and Other Experiments
Christopher M. Savage
Fine Theoretical Physics Institute
University of Minnesota
Katie Freese (University of Michigan)
Graciela Gelmini (UCLA)
Paolo Gondolo (University of Utah)
arXiv:
8/29/08
Cosmo 08 - DAMA and Direct Detection

2. Cosmo 08 - DAMA and Direct Detection
Overview
DAMA/NaI ( )
Observes annual modulation (6.3)  first claimed signal for direct detection of WIMPs
Apparent incompatibilities with other experiments in standard frameworks
Many proposed explanations, including spin-dependent couplings
DAMA/LIBRA (2003+)
Confirms annual modulation (8.2)
Can WIMP scattering still explain both DAMA signal and null results of other experiments?
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3. Cosmo 08 - DAMA and Direct Detection
Outline
WIMP direct detection & modulation
DAMA modulation signal
Explanations and detector effects
Compatibility with other experiments (effective WIMP-nucleon couplings)
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4. Elastic Scattering and WIMP Detection
Direct detection
Annual modulation
Indirect detection (Sun/Earth)
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5. Cosmo 08 - DAMA and Direct Detection
Talk by Uwe Oberlack
Detector
WIMP
Scatter
Goodman & Witten (1985)
Elastic scattering of WIMP off detector nuclei
Rate: X = Ge, Xe, …
Recoils:
Efficiencies, quenching, multiple elements
CDMS, XENON, CRESST, TEXONO, CoGeNT, COUPP, etc.
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6. Cosmo 08 - DAMA and Direct Detection
Recoil spectrum
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7. Cosmo 08 - DAMA and Direct Detection
Annual Modulation
30 km/s
~300 km/s
WIMP Halo Wind
Drukier, Freese & Spergel (1986)
Earth’s motion
With disk (June) Against disk (December)
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8. Cosmo 08 - DAMA and Direct Detection
Annual Modulation
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9. Cosmo 08 - DAMA and Direct Detection
Annual Modulation
DAMA/NaI & DAMA/LIBRA (R. Bernabei et al., 2008)
Modulation amplitude: Sm = ± /kg/day/keVee (2-6 keVee)
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10. Cosmo 08 - DAMA and Direct Detection
Indirect Detection
Silk, Olive & Srednicki (1985), Freese (1986)
Elastic scattering of WIMP off Sun/Earth nuclei  gravitational capture  annihilation (neutrinos)
Flux   X X = H, He, …
SuperK, AMANDA/IceCube, etc. n
WIMP
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11. Cosmo 08 - DAMA and Direct Detection
Indirect Detection
Cross-sections
Gravitational capture  scattering
Annihilation  ann
Assumptions
No large WIMP/anti-WIMP asymmetry
Annihilation cross-section large “enough”
Annihilation not to light quarks
Majorana ()
Relic abundance
<ann v> ~ cm3/s
Majorana ()
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12. Effective Coupling Effective Lagrangian (-quark): SUSY  2q, 3q
Axial vector (spin-dependent)
Scalar (spin-independent)
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13. Scattering Cross-Section
Spin-independent (SI)
Couples to scalar density of quarks and gluons
Scales as A2
MSSM: fp  fn  only one parameter: SI,p
Spin-dependent (SD)
Couples to spin
Multiple form factors due to spins of proton and neutron groups
Does not scale with A
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14. Scattering Cross-Section
Total
Couplings
fp , fn , ap , an  SI,p , SI,n , SD,p , SD,n (+ 2 signs)
SD scattering cross-section for a nucleon typically much larger ( ) than SI cross-section in CMSSM
Indirect detection: Sun is primarily hydrogen
Direct detection: SI A2 boost
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15. Cosmo 08 - DAMA and Direct Detection
DAMA Modulation
DAMA/NaI ( ) R. Bernabei et al., Riv. Nuovo Cim. 26N1, 1 (2003)
Observes annual modulation (6.3)  first claimed signal for direct detection of WIMPs
DAMA/LIBRA (2003+) R. Bernabei et al., arXiv: [astro-ph]
Confirms annual modulation (8.2)
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16. Cosmo 08 - DAMA and Direct Detection
DAMA Modulation
DAMA/NaI (6.3)
Bernabei et al. (2003)
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DAMA Modulation
DAMA/NaI + DAMA/LIBRA (8.2)
Bernabei et al. (2008)
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DAMA Modulation
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DAMA Modulation
Requirements for DM signal
Cosine modulation
1 year period
Phase ~ June 2nd (standard halo)
Modulation at low energies only
Modulation in single scatter events only (not in multiples)
Modulation amplitude  ~7%
Multiple hits
2-6 keVee ± cpd/kg/keVee
High energies
90+ keV ± 0.19 cpd/kg (one cycle)
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20. Cosmo 08 - DAMA and Direct Detection
DAMA Modulation
Backgrounds/systematics
Temperature
Neutrons + other backgrounds
Radon
Muon flux modulation
Detector noise
None reproduce all signal characteristics or capable of producing level of signal
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21. Cosmo 08 - DAMA and Direct Detection
DAMA/NaI
Incompatible?
Standard framework
Spin-independent
Isothermal halo
Cutoff: mass > 30 GeV
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22. Cosmo 08 - DAMA and Direct Detection
DAMA/NaI
Explanations/effects
Low mass WIMPs
P. Gondolo & G. Gelmini, PRD 71, (2005)
Streams/caustics
Gondolo & Gelmini (Ibid)
Spin-dependent couplings
CS, P. Gondolo & K. Freese, PRD 70, (2004)
F. Giuliani & T.A. Girard, PRD 71, (2005)
P. Ullio, M. Kamionkowski & P. Vogel, JHEP 0107, 044 (2001)
Inelastic scattering
D. Tucker-Smith & N. Weiner, PRD 72, (2005)
Mirror matter
R. Foot, PRD 74, (2006)
Etc.
Channeling effect
Migdal effect
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23. Cosmo 08 - DAMA and Direct Detection
Low mass WIMPs
Relax 30 GeV mass cut – scattering off Na
P. Gondolo & G. Gelmini, PRD 71, (2005)
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24. Cosmo 08 - DAMA and Direct Detection
Spin-dependent
Spin-dependent couplings
CS, P. Gondolo & K. Freese, PRD 70, (2004)
F. Giuliani & T.A. Girard, PRD 71, (2005)
P. Ullio, M. Kamionkowski & P. Vogel, JHEP 0107, 044 (2001)
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25. Cosmo 08 - DAMA and Direct Detection
Channeling
Nuclear recoil energy (keV)
Electrons – ionization/scintillation
electron equivalent (keVee)
Other nuclei – phonons/heat
Quenching factor Q:
fraction of recoil energy into measured channel
QNa  0.3, QI   2 keVee DAMA event from:
6.7 keV Na recoil
22 keV I recoil
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26. Cosmo 08 - DAMA and Direct Detection
Channeling
Ion channeling (R. Bernabei et al., 2008)
Recoils along channels in crystal
Energy dependent fraction of recoils have Q  1
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27. Cosmo 08 - DAMA and Direct Detection
DAMA Channeling
Bernabei et al. (2008)
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28. Cosmo 08 - DAMA and Direct Detection
Migdal Effect
Migdal (1941)
Velocity change of recoiling nucleus  excited/ionized electrons
Extra EM energy (ionization/scintillation)
Bernabei et al. (2007)
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29. Cosmo 08 - DAMA and Direct Detection
DAMA Migdal Effect
Bernabei et al. (2008)
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30. Cosmo 08 - DAMA and Direct Detection
DAMA/LIBRA
DAMA/LIBRA analyses (selected)
CS, G. Gelmini, P. Gondolo & K. Freese, arXiv: [astro-ph]
F. Petriello & K.M. Zurek, arXiv: [hep-ph]
S. Chang, A. Pierce & N. Weiner, arXiv: [hep-ph]
D. Hooper, F. Petriello, K.M. Zurek & M. Kamionkowski, arXiv: [hep-ph]
Assumptions
Isothermal spherical halo model
Elastic scattering
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31. Cosmo 08 - DAMA and Direct Detection
DAMA/LIBRA
Binning
Channeling
Statistical methods
Spin-independent (SI)
Spin-dependent (SD)
Proton-only coupling (an = 0)
Neutron-only coupling (ap = 0)
Equal magnitude (an = ±ap)
General couplings
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32. Cosmo 08 - DAMA and Direct Detection
DAMA Binning
DAMA/NaI: 2 bins
Low energy
2-4 keVee ± cpd/kg/keVee
2-5 keVee ± cpd/kg/keVee
2-6 keVee ± cpd/kg/keVee
High energy
6-14 keVee ± cpd/kg/keVee
DAMA/NaI + DAMA/LIBRA: 36 bins
Low energy (2-5 keVee): positive modulation signal
High energy (~6-20 keVee): consistent with zero modulation
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33. Cosmo 08 - DAMA and Direct Detection
DAMA Binning
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34. Cosmo 08 - DAMA and Direct Detection
DAMA Binning
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35. Cosmo 08 - DAMA and Direct Detection
DAMA Binning
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36. Cosmo 08 - DAMA and Direct Detection
DAMA Channeling
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37. Cosmo 08 - DAMA and Direct Detection
DAMA Channeling
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38. DAMA Statistical Tests
Likelihood ratio confidence region
Parameter estimation – preferred region
2 goodness of fit (g.o.f.)
Excluded region
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39. DAMA Statistical Tests
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40. DAMA Statistical Tests
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41. Cosmo 08 - DAMA and Direct Detection
Null Experiments
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Spin-independent
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Spin-independent
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44. Cosmo 08 - DAMA and Direct Detection
Spin-independent
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45. Spin-dependent: proton-only (an = 0)
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46. Spin-dependent: proton-only (an = 0)
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47. Spin-dependent: proton-only (an = 0)
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48. Spin-dependent: neutron-only (ap = 0)
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49. Spin-dependent: neutron-only (ap = 0)
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50. Spin-dependent: neutron-only (ap = 0)
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51. Spin-dependent (an = ap)
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52. Spin-dependent (an = ap)
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53. Spin-dependent (an = -ap)
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54. Spin-dependent (an = -ap)
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55. Spin-dependent couplings
a = 2  N  1 pb a = 20  N  100 pb
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56. Spin-dependent couplings
a = 2  N  1 pb a = 20  N  100 pb
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57. Cosmo 08 - DAMA and Direct Detection
SuperK Analysis
Original:
S. Desai et al. [SuperK Collaboration], PRD 70, (2004)
Analysis down to 10 GeV WIMP mass
No neutrino oscillations
Reanalysis:
D. Hooper, F. Petriello, K.M. Zurek & M. Kamionkowski, arXiv: [hep-ph]
Low WIMP masses
Neutrino Oscillations
Spin-independent
Talk by Kathryn Zurek
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58. Cosmo 08 - DAMA and Direct Detection
(from Kathryn Zurek)
SuperK Analysis
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59. Cosmo 08 - DAMA and Direct Detection
(from Kathryn Zurek)
SuperK Analysis
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60. Cosmo 08 - DAMA and Direct Detection
Results
Parameter spaces still remain which are compatible with DAMA signal and all null results
Spin-independent: GeV (SuperK constrained)
Spin-dependent (proton only): 3-10 GeV (SuperK constrained)
Spin-dependent (neutron only): 7-9 GeV
Spin-dependent (mixed): GeV (SuperK constrained)
Allows for comparable proton and neutron couplings
(e.g. ap = an = 2.5 at 5 GeV)
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61. Cosmo 08 - DAMA and Direct Detection
Conclusions
DAMA can still be explained by low mass WIMPs with spin-independent and/or spin-dependent couplings
Isothermal halo
SuperK further constrains couplings (if valid)
Spin-dependent neutron coupling survives
Probing compatible parameter space:
Odd-Z experiments (SIMPLE/PICASSO, COUPP, KIMS, etc.)
Thresholds more important than exposure
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