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Diurnal and Annual Modulation of Cold Dark Matter Signals

Diurnal and Annual Modulation of Cold Dark Matter Signals. Ling Fu-Sin IDM2004, Edinburgh, Sept. 8th 2004 in collaboration with Pierre Sikivie & Stuart Wick , Phys. Rev. D66, 023504 (2002) (astro-ph/0203448) astro-ph/0405231. Outline. Motivations Solar wakes

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Diurnal and Annual Modulation of Cold Dark Matter Signals

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  1. Diurnal and Annual Modulation of Cold Dark Matter Signals Ling Fu-Sin IDM2004, Edinburgh, Sept. 8th 2004 in collaboration with Pierre Sikivie & Stuart Wick, Phys. Rev. D66, 023504 (2002) (astro-ph/0203448) astro-ph/0405231

  2. Outline • Motivations • Solar wakes • Axion signal modulation • WIMP signal modulation • Conclusions

  3. Motivations • Quest for DM: we need an accurate description of the potential signature. • DM is characterized by two essential properties: • It is collisionless • It has negligible velocity dispersion • Axions • WIMPs

  4. Solar wakes

  5. Effect of the Sun’s gravity on the structure of cold DM flows • Solar wakes: 1 flow upstream, 3 flows downstream • Appearance of caustics: • Spike: line caustic on the axis of symmetry, downstream • Skirt: conical surface near with opening close to the maximum scattering angle

  6. b

  7. Impact parameter vs. polar angle

  8. Flows velocity • From energy and angular momentum conservation with

  9. Flows velocity modulation (on Earth)

  10. Flows velocity modulationDistortion near the spike Flow 4+

  11. Flows density

  12. Flow density modulation (on Earth) Flow 10+

  13. Axion Signal Modulation

  14. Axion detection • Principle: Photoconversion in a strong magnetic field • Photon energy: • Frequency resolution of ADMX detector @ LLNL (in search mode) for • Cavity bandwidth set by the quality factor of the cavity. If one octave is to be covered in one year, the time spent at each frequency is about 100 sec.

  15. Frequency modulation • Relativistic effects • Jupiter & other planets • Earth’s gravity • Earth’s rotation • Earth’s orbital rotation • Earth’s eccentricity • Frequency shift on the measurement time scale

  16. Density modulation • Away from spike • Near spike • Near skirt

  17. WIMP Signal Modulation

  18. WIMP direct detection formulas • Detection by elastic scattering with nuclei • Differential event rate • Total rate with , , • Cold flow with ,

  19. The function T(E) Cold static June December Isothermal

  20. The WIMP Signal modulation for the Caustic ring halo model and the DAMA result Caustic ring halo model: self similar infall halo model with a large number of flows corresponding to particles falling in and out for the nth time P. Sikivie et al., PRD56(1997)1863. P. Sikivie, PLB567(2003).

  21. List of flows

  22. T(E) in the caustic ring halo model

  23. Predicted event rate modulation @ DAMA in the range 2 – 6 keV

  24. Conclusions • DM is collisionless and has negligible velocity dispersion. These features determine the shape of its signal in a detector. • Axion: narrow peak in frequency • WIMP: plateau in the differential event rate • The presence of caustics is potentially crucial for DM discovery.

  25. Axions: Diurnal modulation enables to reconstruct the velocity of the DM flow. It is therefore crucial to include all effects to a precision . • WIMPs: Event rate modulation is very sensitive to thresholds, and can therefore be different with different targets. Caustic ring halo model not incompatible with DAMA: large WIMP masses are favored.

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