Dark Matter: Evidenze, Candidati, Esperimenti

1. Dark Matter: Evidenze, Candidati, Esperimenti Gianpiero Mangano INFN, Sezione di Napoli Italy

2. Summary • A short tour of cosmology • Observational evidences: baryons vs matter • Relic abundance: baryogenesis vs freezing • Candidates • Experiments

3. A basic list of References • C. Jungman, M. Kamionkowski and K. Griest, Phys. Rept. 267 (1996) 195 • G. Bertone, D. Hooper and J. Silk, Phys. Rept. 405 (2005) 279 • S. Dodelson, Modern Cosmology, Academic Press 2003 • J. Peacock, Cosmological Physics, Cambridge University Press 1999 • L. Bergstrom, Rept. Prog. Phys. 63 (2000) 793 • J. Edsjo, Ph.D Thesis, hep-ph/9704384

4. Talks at ISAPP 2006, Sorrento • F. Donato, Dark Matter Particle Physics • C. Galbiati, Direct Dark Matter searches • R. Battiston, Searching for Dark Matter http://isapp06na.na.infn.it/

5. A short tour of cosmology

6. The Universe is spatially flat Primordial perturbations are order 10-5 Main pillars I Cosmic Microwave Background (CMB) anisotropies

7. Main pillars II Big Bang Nucleosynthesis (BBN) Baryons contribute for a very tiny fraction of the total energy

8. Main pillars III Large Scale Structures (LSS) Main pillars III Large Scale Structures (LSS) SDSS Primordial perturbations are of the order of 10-5 and grow by gravitational instability

9. Main pillars IV The Hubble law Main pillars IV The Hubble law The Universe is presently accelerating

10. Cosmology: Einstein Equation (dynamics) Metric (symmetries) Equation of state

11. Friedmann equation: equation for expansion rate H Critical density and energy density fraction Hubble parameter versus redshift z=obs/source-1=1/a-1

12. Observational evidences: baryons vs matter

13. Baryon density • spectra of high redshift quasars • CMB temperature anisotropies • primordial nucleosynthesis b 0.05

14. Matter density I: mass to light ratio

15. From galaxy redshift survey the total luminosity density L 108 h L Mpc-3 Stellar population of galaxies  1 - 10 For a critical Universe, =1 M/L  1400 h For a purely baryonic Universe M/L  20 A lot of dark matter!

16. Matter density II: the galactic scale Rotation curves of (spiral) galaxies Observation of 21 cm hyperfine line in HI clouds Flat behavior, well beyond the visible disk Halo with M  r

17. inner part: cuspy or shallow? N - body numerical simulation predict a steep profile observations suggest a universal density profile with an exponential thin stellar disk and a flat core with density   4.5 10-2 (r0/Kpc)-2/3 M  pc-3

18. Elliptic galaxies: debated! • Some show evidence via strong lensing • X-ray emission support the idea of hot gas clouds whose hydrostatic suggest the presence of DM • Other observations on sub/inter galactic scale • Weak gravitational lensing of distant galaxies by foreground structure • Velocity dispersion of dwarf spheroidal galaxies: high M/L ratio • Velocity dispersion of spiral galaxy satellites

19. Matter density III: the Milky way and the Oort discrepancy Comparison of mass density of stars and gas ( = 0.1 M pc-3) with its dynamical determination via gravitational potential hydrostatic equilibrium Unclear result: at most a factor 2 larger than observed density

20. Matter density IV: the galaxy cluster scale Measures of cluster mass using virial theorem to the observed velocity of galaxies (Zwicky, 1933 first suggestion observing the COMA cluster) High M/L = 400 suggesting   0.2 – 0.3 Measures of X-ray emission tracing hot gas clouds in rich clusters 

21. Check via gravitational lensing (measure total mass) and Sunyaev-Zeldovich effect

22. Matter density V: the cosmological scale Two main observables: CMB temperature fluctuation Power spectrum of structures on large scales

23. WMAP =1 m=0.25 b=0.05

26. Matter density VI: the local density Crucial for direct and indirect measurements of DM Observation of rotation curves of the Milky Way Typical estimated velocity <v2>1/2 270 Km s-1

27. Relic abundance: baryogenesis vs freezing

28. The effect of DM on structure formation depends upon its mass • For collisionless DM • Hot DM (relativistic during a large fraction of structure formation) like neutrinos erase perturbations on small scales and produces a top-down scenario (large structure form first, small structure form via fragmentation) • Cold DM (massive particles > KeV) falls in the initial overdensity gravitational well and produce a bottom–up structure formation scheme (small scale structures form first, large scale via clustering) • CDM scenario is preferred by data: • our galaxy appear to be older than the Local Group • galaxies are observed at redshift as high as z=4

29. How massive particles can have a large abundance today? • thermodynamical equilibrium • two possibilities • some particle – antiparticle asymmetry (baryons): works for CDM • chemical equilibrium is lost for expansion rate is faster than scattering rate at some stage early stage: scenario for both HDM and CDM

30. more popular scenario: relic DM via freezing of interactions

31. Which annihilation rate is required to produce 0.3 ? Departure from equilibrium: Boltzmann equation d/dt nDM = collisions leading to Weak Interacting Massive Particle (WIMP)

32. Candidates

33. Standard Model neutrinos • sterile neutrinos • axions • wimpzillas • SUSY particles: neutralino, gravitino • Kaluza Klein states • light scalar DM • mirror particles • self-interacting DM • light scalar DM • ………………….

34. Neutrinos Cosmological limits on neutrino mass Overdensity for a wide range of mass From 3H decay and oscillation experiments h2 =  0.07 From WMAP and LSS h2  0.007 Only a very small fraction of  can be ascribed to massive neutrinos Neutrinos are HDM

35. Neutralino: the best SUSY candidate • The Standard Model: electroweak and strong interactions • Quarks and leptons (fermions) • Intermediate bosons: 1 massless (photon) + 3 massive (W and Z)+ gluons • Higgs field: spontaneous symmetry breaking mechanism as a mass generating mechanism

36. Motivations • Hierarchy problem • Unification problem

37. General structure How to embed the Poincarè and internal symmetries into a larger non trivial symmetry group? Coleman-Mandula-‘O Rafertaigh Graded Lie algebra Superspace and superfield

38. The Minimal Supersymmetric Standard Model (MSSM) R parity The lightest SUSY neutral particle is stable under decay

39. Constraints from colliders Present…. ….and future

40. Experiments

41. Direct detection: look for scattering of DM off matter elastic scattering: with <v> = 270 Km/s typical energies of tens of KeV inelastic scattering: excitation or ionization after scattering with electrons: recoil + photon emission in ns Spin independent: grows with mass of the target Spin dependent: grows with J(J+1) of the target Indirect detection: products of DM annihilation in the halo, galaxy, Sun gamma-ray experiments neutrino telescopes positron and antiproton experiments radio-experiments (syncrhrotron radiation emitted by electrons and protons propagating in the galactic magnetic field

42. Direct detection Many experiments: scintillation (DAMA, ZEPLIN-I, NAIAD, LIBRA) photons (CREST, DRIFT) ionization (HDMS; GENIUS, IGEX; MAJORANA, DRIFT) mixed tecniques (CDMS, Edelweiss, WARP, ZEPLIN-II, ZEPLIN-III, ZEPLIN-MAX)

45. CDMS Genius WARP Zeplin-I CRESST-II Zeplin-max Edelweiss-I CDMS-Soudan Edelweiss-II

47. Indirect detection I: Gamma-ray experiments Space-based: in the GeV-TeV range photons interact with matter via pair production (interaction length 38 g cm-2) EGRET, GLAST Ground-based: look for e.m. cascade via Cerenkov light. Large background due to ordinary isotropic Cosmic Rays. MC simulation

50. Indirect detection II: Neutrino Telescopes: Km3 experiments looking for Cerenkov light of muon tracks after v interaction under ice under water Amanda, ICECUBE Antares, Nemo, Nestor