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Detecting galactic structure via the annual modulation signal of WIMPs

Detecting galactic structure via the annual modulation signal of WIMPs. Christopher M. Savage Fine Theoretical Physics Institute University of Minnesota. Katie Freese (University of Michigan) Paolo Gondolo (University of Utah) PRD 74 , 043531 (2006). Overview.

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Detecting galactic structure via the annual modulation signal of WIMPs

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  1. Detecting galactic structure via the annual modulation signal of WIMPs Christopher M. Savage Fine Theoretical Physics Institute University of Minnesota Katie Freese (University of Michigan) Paolo Gondolo (University of Utah) PRD 74, 043531 (2006) GLCW8

  2. Overview Galactic dark matter halo • Early collapse of of dark matter virialized  smooth/diffuse halo (position & velocity space) • Turbulent; late accretion  streams (“cold” flow) • Clumps • Tidal streams • Caustics WIMP direct detection signatures • Energy • Time (annual modulation) GLCW8

  3. D. Dixon, cosmographica.com Halo • Galaxy formation gravitational collapse • Standard Halo Model • Isothermal sphere • Non-rotating GLCW8

  4. D. Martinez-Delgado & G. Perez V. Springer Halo Substructure • Tidal streams • Dwarf galaxies • Sagittarius Stream • Clumps • Hierarchical clustering • Caustics Newberg et al. (2003) Freese, Gondolo & Newberg (2003) Klypin et al. (1999); Moore et al. (1999) Stiff, Widrow & Frieman (2001) Gunn & Gott (1972) Sikivie, Tkachev & Wang (1995,1997) GLCW8

  5. Halo • Smooth halo component (dominant?) + streams / “cold” flows • Local DM density: <> ~ 0.3 GeV/cm3Typical velocities: v ~ 100’s km/s • Local velocity distribution:Mean inverse velocity: GLCW8

  6. Halo • Velocity distribution GLCW8

  7. Halo • Mean inverse velocity GLCW8

  8. Detector WIMP Scatter WIMP astrophysics particle physics Direct Detection Goodman & Witten (1985) • Elastic scattering of WIMP off detector nuclei • Rate: • CDMS, CRESST, DRIFT, EDELWEISS, NAIAD, PICASSO,SIMPLE, XENON, ZEPLIN, etc. GLCW8

  9. 30 km/s WIMP Halo Wind ~300 km/s Annual Modulation Drukier, Freese & Spergel (1986) • Earth’s motion • With disk (June)Against disk (December) • DAMA/NaI (R. Bernabei et al., 2003) Modulation amplitude: 0.0200 ± 0.0032 /kg/day/keVee (2-6 keVee) • DAMA/LIBRA GLCW8

  10. Standard Halo Model (SHM) Freese, Frieman & Gould (1988) • Non-rotating, isothermal sphere v = 270 km/s 0 = 0.3 GeV/cm3 () • Detector velocity: vdet(t) = vŸ + V(t) • Sun’s velocity vŸ (disk rotation ~220 km/s) • Earth’s orbital velocity V(t) • Characteristic time tc: vobs maximum (June 1 for SHM) GLCW8

  11. Phase reversal Small modulation amplitude (few percent) Mean Inverse Speed: SHM GLCW8

  12. Characteristic time tc(June 1) Modulation: SHM GLCW8

  13. APOD 9/30/03 (Martinez-Delgado & Perez) …Add a Stream • Sagittarius (Sgr) stream Yanni et al (2003) • Sagittarius-like stream(for illustration) • Direction & speed (~340 km/s) • Dispersion: v = 25 km/s • Density: Sgr = 0.05 SHM • Sgr stream: 0.3-25% Freese, Gondolo & Newberg (2003) • Clumps: 1-5% Stiff, Widrow & Frieman (2001) • Caustic ring model: ~75% Sikivie, Tkachev & Wang (1995) GLCW8

  14. Characteristic EnergyEc = <Eco(t)> (39 keV) Cutoff Energy Eco(t) Mean Inverse Speed: SHM + Streamno dispersion (v = 0) GLCW8

  15. Mean Inverse Speed: SHM + Streamwith dispersion (v > 0) GLCW8

  16. Modulation: SHM + Stream 5% Stream!!! GLCW8

  17. Characteristic time tc (Dec 28) Modulation: Recoil Energy • Sgr stream modulation GLCW8

  18. Modulation: Recoil Energy • Total modulation GLCW8

  19. Modulation: Recoil Energy Binning GLCW8

  20. Modulation: Stream Density GLCW8

  21. General Streams / Cold Flows • Phase of modulation (tc) independent of SHM • Rapid dropoff in count rate near some characteristic energy Ec • Small, cosine-like modulation below Ec • Large O(1) modulation near Ec (not cosine-like) • Ec, tc differ from Sagittarius stream GLCW8

  22. Extracting Parameters • Characteristic energy Ec cold flow speed • Characteristic time tc cold flow direction (1 component) • Modulation amplitude  relative densities (Str / SHM) • More difficult: • cold flow dispersion • 2nd direction component GLCW8

  23. Summary • Local Halo: presence of streams / cold flows • Small component • Annual modulation • Mild effect • …except near some characteristic energy: • Relatively large effect • Not cosine-like • Modulation detection: probe structure of halo • …sooner! GLCW8

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