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Progress of dark matter research

2nd Korea-China joint seminar on Dark Matter Search. Progress of dark matter research. Xuelei Chen 陳學雷 National Astronomical Observatory of China. Nov 24, 2007 Seoul National University. Outline. A brief Review of DM problem Some Cosmological Constraints on non-conventional DM

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Progress of dark matter research

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  1. 2nd Korea-China joint seminar on Dark Matter Search Progress of dark matter research Xuelei Chen 陳學雷 National Astronomical Observatory of China Nov 24, 2007 Seoul National University

  2. Outline • A brief Review of DM problem • Some Cosmological Constraints on non-conventional DM • Suggestion on searching for Light DM

  3. Evidences of dark matter

  4. Most Dark matter is not ordinary matter (baryon) BBN & CMB: baryon is only 4-5%

  5. Can neutrinos be the dark matter ? at freeze-out if weakly interacting hot dark matter relativistic m< 1 keV warm dark matter quasi-relativistic 1 keV < m < 10 keV cold dark matter non-relativistic m > 10 keV at freeze-out Pure HDM(light neutrino) is excluded. CDM, WDM, and mixtures are possible. Tegmark et al (SDSS), astro-ph/0608632

  6. Weakly Interacting Massive Particle (WIMP)? dark -- weakly interacting? cold -- massive (non-relativisitic) abundance @ early Universe freeze out when H = n <Av>, lightest supersymmetric particle (neutralino, gravitino, sneutrino, ...?) Kaluza-Klein particle?

  7. Dark Matter or MOND? Testing modified gravity: bullet cluster (Clowe et al astro-ph/0608407) Improbable as it is, all other explanations are more improbable still. --Sherlock Holmes

  8. Searching for DM:WIMP direct search • DM can penetrate shielded (underground) detectors • detecting single atom collision: • elastic--phonons and heat • inelastic -- ionization/excitation • identification/annual modulation DAMA, CDMS, Edelweiss, CRESST, KIMS, ZEPLIN, XENON...

  9. Indirect Search Gamma-Ray from DM annihilation High Energy Neutrino from DM annihilation Cosmic Ray from DM annihilation GLAST

  10. Challenge to CDM: halo profile NFW96, rotation curve simulation (Navarro, Frenk, white 1996): cusp • Is density profile really universal? • What is the real slope • NFW: 1.0 Moore 1.5 • Observation • beam smearing? 21cm, H, CO • some agree w/ cusp, but most dwarf • has core (slope 0.2) • Cusp cheat as core • vg != vc , because of inclination, effect of bulge and bar, gas supported by pressure, star orbit in triaxial halo, ...

  11. Challenge to CDM: halo substructure Simulation indicates 102-3 DM subhalo in Local Group, but observed satellites ~ 20 • satellites do exist, but star formation suppressed (after reionization?) • satellites orbit do not bring them to close interaction with disk, so they will not heat up the disk. • Local Group dwarf velocity dispersion underestimated • halo substructure may be probed by lensing (still controversial) B. Moore et al 1997

  12. Dwarf galaxies Nearly 20 new dwarf galaxies discovered Updated Mateo plot minimal mass of DM halo for dwarf galaxies 5 x 107 Msun Core and low phase space density in dwarf galaxies Gilmore et al 2007

  13. But ... Simon & Geha 2007

  14. Missing satellite problem solved? Simon & Geha 2007

  15. Alternatives Warm Dark Matter, Self-Interacting Dark Matter Strongly Interacting Massive Particle Annihilating DM Decaying DM Fuzzy DM Light DM ...

  16. Test DM interaction with CMB and LSS XC, Hannestad, Scherrer 2002

  17. z ~ 1000 z ~ 30 z ~ 6 z ~ 0 Cosmic Ionization History: constraint on DM decay/annihilation ?

  18. DM decay affects reionization XC & Kamionkowski 2004

  19. Constraint on DM decay XC & Kamionkowski 2004 L. Zhang et al. 2007

  20. Light (MeV) Dark Matter? If dark matter mass is 1-100 MeV instead of 100 GeV (neutralino), then the number density is much higher. Annihilation rate ~ n2 (Boehm, Hooper, Silk 2003) INTEGRAL observation of GC 511 keV line: where does the positron come from?

  21. CMB Constraint on Light Dark Matter homogenous annihilation during recombination Impact on reionization L. Zhang et al. 2006

  22. Presense of a new interaction? • supersymmetric version of • SU(3) x SU(2) x U(1) x U(1) • mU ~ MeV • vector gauge coupling ~ 10-6 • U-boson coupling allow greater DM annihilation rate, leads to the correct abundance P. Fayet astro-ph/0702176

  23. U-boson mediated interaction of MeV dark matter Ek ~ MDM v2 • Cross section about 102 times WIMP (assume mass ~ MW) interaction mediated by W • Collision Rate ~ cross section/mass, about 106 times WIMP collision rate

  24. A new possibility: direct search of Light DM • Light Dark Matter mass: 1-100 MeV • interaction: weak interaction, or new interaction (e.g. mediated by U-boson) • Direct Search have so far been limited to m>10 GeV • Need develop technology to constrain this part of parameter space

  25. Nuclear Recoil Pulse Approximation: nucleus obtain a sudden speed Elastic: The whole atom moves, no excitation, energy is dissipated as phonons and/or heat Inelastic: Some energy is converted to ionization and/or excitation.

  26. Recoil Energy very small For each set of 5 curves, assume detector nuclei of mass 10, 20, 40, 80, 160 GeV

  27. Recoil with Electron DM scattering with electron:

  28. Discussions • Need to detect very small recoil energy: 1-10 eV • Nuclear Recoil and Electron Recoil detect different interaction • Method of detection? Suggestions Welcome! • What is the background?

  29. Thanks!

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