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The Search for Dark Matter with GLAST LAT

Learn about the Gamma Ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) and how it can be used to search for dark matter. Explore the gamma-ray sky, find out where to look for dark matter, and discover the collaboration behind GLAST LAT.

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The Search for Dark Matter with GLAST LAT

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  1. The Search for Dark Matter Using the Gamma Ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Ping Wang KIPAC-SLAC, Stanford University Representing GLAST LAT Collaboration Dark Matter and New Physics Working Group DPF 06, Wang

  2. Overview • What is GLAST LAT? • How dose dark matter shine in the gamma ray sky? • Where should we look for dark matter with GLAST? • Summary DPF 06, Wang

  3. GLAST LAT Collaboration Principal Investigator: Peter Michelson (Stanford & SLAC) ~225 Members (includes ~80 Affiliated Scientists, 23 Postdocs, and 32 Graduate Students) • France • IN2P3, CEA/Saclay • Italy • INFN, ASI • Japan • Hiroshima University • ISAS, RIKEN • United States • California State University at Sonoma • University of California at Santa Cruz - Santa Cruz Institute of Particle Physics • Goddard Space Flight Center – Laboratory for High Energy Astrophysics • Naval Research Laboratory • Ohio State University • Stanford University (SLAC and HEPL/Physics) • University of Washington • Washington University, St. Louis • Sweden • Royal Institute of Technology (KTH) • Stockholm University Cooperation between NASA and DOE, with key international contributions from France, Italy, Japan and Sweden. LAT Managed at Stanford Linear Accelerator Center (SLAC) DPF 06, Wang

  4. GLAST is a NASA Mission • Launch: September 2007 • Lifetime: 5-years (10-years goal) • Orbit: 565 km, circular • Inclination: 28.5o Large Area Telescope (LAT) 20 MeV - 300 GeV • GLAST is the next generation after EGRET… factor > 30 improvement in sensitivity • Large effective area, factor > 5 better than EGRET • Field of View ~20% of sky, factor 4 greater than EGRET • Point Spread function factor > 3 better than EGRET for E>1 GeV. On axis >10 GeV, 68% containment < 0.12 degrees • Minimize rejection of E>10GeV gamma rays due to backscatter into cosmic ray shield • No expendables (EGRET had spark chamber gas) - long mission without degradation (5-10 years) GLAST Burst Monitor (GBM) 8 keV - 30 MeV DPF 06, Wang

  5. e+ e– GLAST Large Area Telescope (LAT)20 MeV – 300 GeV • Anti-Coincidence Detector • 4% R.L. • 89 scintillating tiles • efficiency (>0.9997) for MIPs 1.8 m • Tracking detector • 16 tungsten foils (12x3%R.L.,4x18%R.L.) • 18 pairs of silicon strip arrays • 884736 strips (228 micron pitch) 1.0 m • Calorimeter • 8.5 radiation lengths • 8 layers cesium iodide logs • 1536 logs total (1200kg) DPF 06, Wang

  6. Indirect detection – a complementary way to observe dark matter signals! DPF 06, Wang

  7. + a few p/p, d/d WIMP annihilation: continuum spectrum • Dominant mode for Majorana fermion WIMPs: g time p0 g W-/Z/q c } nm nmne p+ m+ e+ _ nm c nmne W+/Z /q p- m- e- DPF 06, Wang

  8. g p0 g t- nt nm nmne p- m- e- c WIMP annihilation: continuum spectrum • Additional dominant mode for Dirac fermion or boson WIMPs: time nm/tne c n/e-/m-/t- m/t- } or e- nm/tne n/e+/m+/t+ m/t+ e+ DPF 06, Wang

  9. γ c ? c Z0 WIMP annihilation: spectral lines time g,e+,n • For gg lines, energy = WIMP mass; branching fraction is suppressed • e+e-, nn lines are possible at tree level; but suppressed for Majorana fermions • For WIMP masses > MZ /2 can also have gZ0 line • Measurement of line branching fractions would constrain particle theory c ? c g,e-,n DPF 06, Wang

  10. WIMP annihilation: gamma-ray flux • Photon flux from WIMP annihilation: Ann. Cross-section (cosmology, particle phys) Ann. Spectrum (particle physics) WIMP number density ^2 (astrophysics, particle phys) DPF 06, Wang

  11. Gamma ray yield per final state bb WIMP annihilation: gamma-ray yield 200GeV mass WIMP WIMP pair annihilation gamma spectrum DPF 06, Wang

  12. Dark Matter in the gamma ray sky Milky Way Halo simulated by Taylor & Babul (2005) All-sky map of DM gamma ray emission (Baltz 2006) Galactic center Milky Way satellites Milky Way halo Extragalactic DPF 06, Wang

  13. Diffuse gamma ray background EGRET Eg>1GeV, point-source subtracted, Cillis & Hartman (2005) Modeling with GALPROP Inputs include matter distribution DPF 06, Wang

  14. Galactic satellites – seen and… unseen? Moore, et.al. (1999) (M=5x1014Msun, R=2000kpc) (M=2x1012Msun, R=300kpc) Should be ~500 satellites w/ M>107Msun… Where are they? (Galaxies within Virgo) visible satellites (faint) V=(GMbound/Rbound)0.5 DPF 06, Wang

  15. Simulation Example: DM Satellite 55-days GLAST in-orbit counts map (E>1GeV) Galactic Center Optimistic case: 70 counts signal, 43 counts background within 1.5 deg of clump center 30-deg latitude DPF 06, Wang

  16. GLAST 55 days (10-sigma) Dark matter spectrum Diffuse background E-2.6 spectrum DM satellite energy spectrum DPF 06, Wang

  17. Observable DM satellites (estimate) • Simulation of Milky Way dark matter satellites from Taylor & Babul, 2004, 2005 • SUSY model benchmark definitions LCC# from Baltz, et al, 2006 • Background estimate using EGRET above 1GeV (point-source subtracted) from Cillis & Hartman 2005 • Signal, background flux inside the tidal radius • LCC2 and LCC4 are much more favorable to GLAST than LCC1 and LCC3 LSP WIMP (SUSY) GLAST 5-yrs LCC2 LCC4 DPF 06, Wang

  18. Summary • GLAST LAT offers a unique opportunity to discover WIMP dark matter by the gamma rays produced in pair annihilations • GLAST collaboration will search for WIMP annihilation gamma rays from galactic center, galactic halo, galactic satellites and extragalactic DPF 06, Wang

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