6/2/07GLCW8 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, (2006)

6/2/07GLCW8 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)

6/2/07GLCW8 3 Halo Galaxy formation gravitational collapse Standard Halo Model Isothermal sphere Non-rotating D. Dixon, cosmographica.com

6/2/07GLCW8 4 Halo Substructure Tidal streams Dwarf galaxies Sagittarius Stream Clumps Hierarchical clustering Caustics D. Martinez-Delgado & G. Perez Newberg et al. (2003) Freese, Gondolo & Newberg (2003) Klypin et al. (1999); Moore et al. (1999) Stiff, Widrow & Frieman (2001) V. Springer Gunn & Gott (1972) Sikivie, Tkachev & Wang (1995,1997)

6/2/07GLCW8 5 Halo Smooth halo component (dominant?) + streams / “cold” flows Local DM density: ~ 0.3 GeV/cm 3 Typical velocities: v ~ 100’s km/s Local velocity distribution: Mean inverse velocity:

6/2/07GLCW8 6 Halo Velocity distribution

6/2/07GLCW8 7 Halo Mean inverse velocity

6/2/07GLCW8 8 Direct Detection Elastic scattering of WIMP off detector nuclei Rate: CDMS, CRESST, DRIFT, EDELWEISS, NAIAD, PICASSO,SIMPLE, XENON, ZEPLIN, etc. Detector WIMP Scatter Goodman & Witten (1985) particle physicsastrophysics

6/2/07GLCW8 9 Annual Modulation Earth’s motion With disk (June) Against disk (December) DAMA/NaI (R. Bernabei et al., 2003) Modulation amplitude: ± /kg/day/keVee (2-6 keVee) DAMA/LIBRA 30 km/s ~300 km/s WIMP Halo Wind Drukier, Freese & Spergel (1986)

6/2/07GLCW8 10 Standard Halo Model (SHM) Non-rotating, isothermal sphere  v = 270 km/s  0 = 0.3 GeV/cm 3 (    ) Detector velocity: v det (t) = v  + V  (t) Sun’s velocity v  (disk rotation ~220 km/s) Earth’s orbital velocity V  (t) Characteristic time t c : v obs maximum (June 1 for SHM) Freese, Frieman & Gould (1988)

6/2/07GLCW8 11 Mean Inverse Speed: SHM Phase reversal Small modulation amplitude (few percent)

6/2/07GLCW8 12 Modulation: SHM Characteristic time t c (June 1)

6/2/07GLCW8 13 …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: % Freese, Gondolo & Newberg (2003)  Clumps: 1-5% Stiff, Widrow & Frieman (2001)  Caustic ring model: ~75% Sikivie, Tkachev & Wang (1995) APOD 9/30/03 (Martinez-Delgado & Perez)

6/2/07GLCW8 14 Mean Inverse Speed: SHM + Stream no dispersion (  v = 0) Cutoff Energy E co (t) Characteristic Energy E c = (39 keV)

6/2/07GLCW8 15 Mean Inverse Speed: SHM + Stream with dispersion (  v > 0)

6/2/07GLCW8 16 Modulation: SHM + Stream 5% Stream!!!

6/2/07GLCW8 17 Modulation: Recoil Energy Sgr stream modulation Characteristic time t c (Dec 28)

6/2/07GLCW8 18 Modulation: Recoil Energy Total modulation

6/2/07GLCW8 19 Modulation: Recoil Energy Binning

6/2/07GLCW8 20 Modulation: Stream Density

6/2/07GLCW8 21 General Streams / Cold Flows Phase of modulation (t c ) independent of SHM Rapid dropoff in count rate near some characteristic energy E c Small, cosine-like modulation below E c Large O(1) modulation near E c (not cosine-like) E c, t c differ from Sagittarius stream

6/2/07GLCW8 22 Extracting Parameters Characteristic energy E c  cold flow speed Characteristic time t c  cold flow direction (1 component) Modulation amplitude  relative densities (  Str /  SHM ) More difficult: cold flow dispersion 2 nd direction component

6/2/07GLCW8 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!