Quest for Dark Matter with Cosmic Gamma-ray Observations Hiroyasu Tajima Solar-Terrestrial Environment Laboratory Nagoya University December 11–13, 2013 KMI International Symposium 2013 on “Quest for the Origin of Particles and the Universe” Nagoya University, Nagoya, Japan
Outline ✤ Introduction ✤ Cosmic gamma-ray experiments ❖ Fermi Gamma-Ray Space Telescope ❖ Imaging atmospheric Cherenkov telescopes (IACTs) ✤ WIMP searches with Fermi ✤ WIMP search with IACT ✤ Future prospects Quest for Dark Matter with Cosmic Gamma-ray Observations 2 /21 KMI2013, DEC 11–13, 2013, Nagoya
X-ray image Coma Dark Matter ✤ What we know ❖ Dark matter exists • Orbital velocities of stars in galaxies, velocity dispersions of galaxies in clusters, temperature distribution of hot gas in clusters of galaxies and gravitational lensing ❖ Non-relativistic (“cold dark matter”) ❖ ~6 x ordinary matter Credit: NASA/CXC/M.Weiss) ✤ What we don’t know ❖ What is dark matter? • MACHO: constrained by micro-lensing • WIMP - Weak scale new particles happen to have suitable mass and cross-section WIMP miracle • Axion Galaxy cluster (optical) Quest for Dark Matter with Cosmic Gamma-ray Observations 3 /21 KMI2013, DEC 11–13, 2013, Nagoya
X-ray image Coma Dark Matter ✤ What we know ❖ Dark matter exists • Orbital velocities of stars in galaxies, velocity dispersions of galaxies in clusters, temperature distribution of hot gas in clusters of galaxies and gravitational lensing ❖ Non-relativistic (“cold dark matter”) ❖ ~6 x ordinary matter Credit: NASA/CXC/M.Weiss) ✤ What we don’t know ❖ What is dark matter? • MACHO: constrained by micro-lensing • WIMP - Weak scale new particles happen to have suitable mass and cross-section WIMP miracle • Axion Mass distribution by gravitational lensing Quest for Dark Matter with Cosmic Gamma-ray Observations 3 /21 KMI2013, DEC 11–13, 2013, Nagoya
X-ray image Coma Dark Matter ✤ What we know ❖ Dark matter exists • Orbital velocities of stars in galaxies, velocity dispersions of galaxies in clusters, temperature distribution of hot gas in clusters of galaxies and gravitational lensing ❖ Non-relativistic (“cold dark matter”) ❖ ~6 x ordinary matter Credit: NASA/CXC/M.Weiss) ✤ What we don’t know ❖ What is dark matter? • MACHO: constrained by micro-lensing • WIMP - Weak scale new particles happen to have suitable mass and cross-section WIMP miracle • Axion Hot gas distribution (imaged by X-ray) Quest for Dark Matter with Cosmic Gamma-ray Observations 3 /21 KMI2013, DEC 11–13, 2013, Nagoya
X-ray image Coma Dark Matter ✤ What we know ❖ Dark matter exists • Orbital velocities of stars in galaxies, velocity dispersions of galaxies in clusters, temperature distribution of hot gas in clusters of galaxies and gravitational lensing ❖ Non-relativistic (“cold dark matter”) ❖ ~6 x ordinary matter Credit: NASA/CXC/M.Weiss) ✤ What we don’t know ❖ What is dark matter? • MACHO: constrained by micro-lensing • WIMP - Weak scale new particles happen to have suitable mass and cross-section WIMP miracle • Axion Quest for Dark Matter with Cosmic Gamma-ray Observations 3 /21 KMI2013, DEC 11–13, 2013, Nagoya
X-ray image Coma Dark Matter ✤ What we know ❖ Dark matter exists • Orbital velocities of stars in galaxies, velocity dispersions of galaxies in clusters, temperature distribution of hot gas in clusters of galaxies and gravitational lensing ❖ Non-relativistic (“cold dark matter”) ❖ ~6 x ordinary matter Credit: NASA/CXC/M.Weiss) ✤ What we don’t know ❖ What is dark matter? • MACHO: constrained by micro-lensing • WIMP - Weak scale new particles happen to have suitable mass and cross-section WIMP miracle • Axion Quest for Dark Matter with Cosmic Gamma-ray Observations 3 /21 KMI2013, DEC 11–13, 2013, Nagoya
WIMP Search Approaches ✤ Accelerator production ❖ Precise measurements of “DM” properties: mass, cross section ❖ UED (KK) vs SUSY ✤ Direct detection of WIMP scattering ❖ Measurement of local WIMP density ✤ Indirect detection of WIMP annihilation ❖ “Direct” constraints on annihilation cross section SM ❖ Distribution of WIMP in the Universe Production particle WIMP particle physics dN f < σ ann v > d Φ γ 1 γ ( E γ , φ , θ ) = B f 2 m 2 dE γ 4 π dE γ Scattering W I M P f ρ 2 ( r ( l, φ )) dl ( r, φ ) × d Ω ∆Ω ( φ , θ ) los WIMP DM distribution SM particle ✤ Those approaches are complimentary Annihilation ❖ Different model dependences and sensitivity phase space Quest for Dark Matter with Cosmic Gamma-ray Observations 4 /21 KMI2013, DEC 11–13, 2013, Nagoya
Thermal Relic Dark Matter (WIMP) ✤ WIMP is in equilibrium between pair creation and annihilation in early Universe ❖ Pair creation stops when thermal energy is not sufficient ❖ Annihilation continues and WIMP density become too low compared with annihilation cross section • WIMP density and annihilation cross section is anti-correlated ❖ Current dark matter density ( Ω DM ) t (ns) 10 0 10 1 10 2 10 3 10 8 constrains annihilation cross m X = 100 GeV WIMP density/Entropy density 10 –4 section to ~3x10 − 26 cm 2 /s JONATHAN L. FENG 10 6 10 –6 10 4 Small cross section 10 –8 10 2 Ω X Y 10 –10 10 0 10 –12 10 –2 10 –14 Large cross section 10 –4 10 –16 10 1 10 0 T (GeV) Quest for Dark Matter with Cosmic Gamma-ray Observations 5 /21 KMI2013, DEC 11–13, 2013, Nagoya
Search for WIMP with Gamma Rays ✤ Multi-pronged approaches ❖ Galactic center, Milky Way halo, Satellites ❖ Line emission, Continuum ❖ CR electrons, Diffuse gamma-ray background Milky Way halo: Large statistics but diffuse background Galactic center: Good Statistics but source Satellites : confusion/diffuse background Low background and good source id, but low statistics, astrophysical background Good Statistics but source confusion/diffuse background Quest for Dark Matter with Cosmic Gamma-ray Observations 6 /21 KMI2013, DEC 11–13, 2013, Nagoya
Search for WIMP with Gamma Rays ✤ Multi-pronged approaches ❖ Galactic center, Milky Way halo, Satellites ❖ Line emission, Continuum ❖ CR electrons, Diffuse gamma-ray background Milky Way halo: Large statistics but diffuse background Galactic center: Good Statistics but source Satellites : confusion/diffuse background Low background and good source id, but low statistics, astrophysical background Good Statistics but source confusion/diffuse background Quest for Dark Matter with Cosmic Gamma-ray Observations 6 /21 KMI2013, DEC 11–13, 2013, Nagoya
Fermi LAT (Large Area Telescope) ✤ Pair-conversion telescope ❖ Good background rejection due to “clear” gamma-ray signature ✤ Tracker (TKR): pair conversion, tracking ❖ Angular resolution is dominated by scattering below ~GeV ✤ Calorimeter: energy measurement Si Tracker ❖ 8.4 radiation length 70 m 2 , 228 µm pitch γ ~0.9 million channels ❖ Use shower development (Japanese contribution) to compensate for the leakage ✤ Anti-coincidence detector: Large Area ❖ Efficiency > 99.97% Telescope (LAT) Energy band: 20 MeV to >300 GeV Effective area: > 8000 cm2 (~6xEGRET) Field of view: > 2.4 sr (~5xEGRET) e - Angular resolution: 0.04 – 10° e + Energy resolution: 5 – 10% Anti-coincidence Detector Gamma-ray Segmented scintillator tiles CsI Calorimeter Burst 99.97% efficiency 8.4 radiation length Monitor Quest for Dark Matter with Cosmic Gamma-ray Observations 7 /21 KMI2013, DEC 11–13, 2013, Nagoya
Fermi/LAT Collaboration Stanford University & SLAC NASA Goddard Space Flight Center Naval Research Laboratory University of California at Santa Cruz ~400 Scientific Sonoma State University Members (including University of Washington 96 Affiliated Scientists, Purdue Univeristy-Calumet plus 68 Postdocs and Ohio State University 105 Students) University of Denver Commissariat a l’Energie Atomique, Saclay CNRS/IN2P3 (CENBG-Bordeaux, LLR-Ecole polytechnique, LPTA-Montpellier) Hiroshima University Nagoya University Institute of Space and Astronautical Science Tokyo Institute of Technology RIKEN Instituto Nazionale di Fisica Nucleare Agenzia Spaziale Italiana Istituto di Astrofisica Spaziale e Fisica Cosmica Royal Institute of Technology, Stockholm Stockholms Universitet Quest for Dark Matter with Cosmic Gamma-ray Observations 8 /21 KMI2013, DEC 11–13, 2013, Nagoya
Highlights of Fermi Science Test of Lorentz Invariance Violation IC 443 (a) -10 10 4 10 ) -1 s -2 dN/dE (erg cm 3 Energy (MeV) 10 -11 10 cosmic-ray origin 2 10 Best-fit broken power law 2 Fermi-LAT E VERITAS (Acciari et al. 2009) MAGIC (Albert et al. 2008) -12 10 AGILE (Tavani et al. 2010) 10 0 -decay � Bremsstrahlung -0.03 0.53 0.63 0.73 Bremsstrahlung with Break 8 9 10 11 12 GBM NaIs 10 10 10 10 10 (b) Energy (eV) cosmic-ray electron spectra cosmic-ray e ± spectra 10 100 Energy Quest for Dark Matter with Cosmic Gamma-ray Observations 9 /21 KMI2013, DEC 11–13, 2013, Nagoya
Imaging Atmospheric Cherenkov Telescope Cherenkov Light 50 photons/m 2 (5 pe/m 2 ) at 1TeV T1 T � T � T � Typical parameters Energy range 50GeV ~ 10TeV Angular resolution ~0.1 degrees Energy resolution ~20% Detection area ~10 5 m 2 Field of view ~4° (~10 -2 sr) Quest for Dark Matter with Cosmic Gamma-ray Observations 10 /21 KMI2013, DEC 11–13, 2013, Nagoya
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