Bangs and Bumps: looking for dark matter in our neighborhood

2. Bangs and Bumps: looking for dark matter in our neighborhood Peter Fisher Nov. 11, 2004

3. Outline • A word about “dark matter’’ and “relics’’ and an example particle • Bumps: nuclear recoil • Cosmological relics - Example: Dirac neutrino • Spin dependent interactions - Example: Majorana neutrinos • Bangs: annihilation • Bumps and Bangs: terrestrial and solar capture

4. A word about “dark matter’’… • Fritz Zwicky (1933): Galactic dynamics • Rotation curves • Cluster infall velocities • Perpendicular velocities • Lensing • By “Dark Matter”, I mean • g=0.15-0.60 GeV/cm3 • No strong or EM interactions • Vave=250 km/s

5. Particles produced early in the Big Bang • In equilibrium with photons when T>>M • “Freeze out” (no change in total number of particles) when T<<M • no depends on details of the theory • Play no further role • Known gCMB, ne, nm and nt • Unknown m>1 GeV …and “relics” Equilibrium between massive relics and photons before freeze out: May be dark matter or part of dark matter

6. Example particle • For concreteness, will talk about fourth generation sequential neutrino and partner lepton • Same couplings asne, nmand nt • MarkII/SLD/LEP measurements: mn>45 GeV • Partner lepton heavier, mL> mn, neutrino stable

7. Relics Estimates for stable relic particles (G.Borner, “The Early Universe: Facts and Fiction”)

8. Bumps: nuclear recoil experiments

9. An extreme environment Goal:create an instrumented region of matter free of terrestrial interactions. • Example: crystal lattice. • Excitations: • Ionization electrons, photons • Phonons • Other extreme environments: • Cold, isolated - B.E.C. • Hot, dense - heavy ion Strong interactions EM interactions

10. Eion/Eph+Eion 1 1/3 Eph+Eion Experiment Detection:discriminate between electrons, photons (EM only) and phonons (EM, strong) EM Shield:OHFC copper, Lead Neutron Shield: muon veto, Depth Phonon shield : cold

11. Look for Relic • M>50 GeV • Vave=250 km/s • Maxwell-Boltzmann velocity distribution • Spin? • Coupling? • Density?

12. CDMS (2004)

13. Detectors (Edelweiss) Cold finger Ge sensor (70 g ) • Typical mass 70-250 g • Si or Ge • One side: ionization • Other side: array of transition edge sensors Ge sensor (70 g )

14. Signal… Kinematics: Where R=nuclear radius b*=CM velocity Coherence: TR<40 keV for typical nucleus • ET<300 keV • Recoil - Eion~Ephonon/2 • Then: • Must be weak interaction (shielding) • Slow (p small, coherent) • Massive (nucleus~10-100 GeV recoils) Can only be a relic from the Big Bang Not necessarily dark matter

15. Recoil Energy Spectrum Relic density Velocity weighted scattering rate Number target nuclei Measuring time • All the measurement is in the first bin, need to get threshold a low as possible • Exposure time measured in kg-day • f(v)=Maxwell-Boltzmann (best guess)

16. Annual variation in count rate January June • Sun moves through galaxy rest frame ~250 km/s • Earth moves around Sun at 30 km/s • Very small effect • Claimed observation by DAMA, rate measurements by others contradict 20 keV

17. Example: nD as dark matter • First attempt (1988): • Ionization only • Assume r=0.3 GeV/cm3 • Extract cross section limit assuming no signal

18. Limits on very massive neutrinos 15 years later… …limits from most recent Particle Data Book rely on assumption massive n is dark matter… …look at current experiments and move above the line

19. nD as a relic CDMS 2004 Take no=10-4 GeV2/mn, assume n clumps like matter Use CDMS 2004 experiment data: no recoils observed with TR>10 keV mn<500 GeV at 90% c.l. - Particle Physics result!

20. Dirac and Majorana Particles • Since chargeless, can form: • Consequences: • Lepton number not conserved • Entirely different coupling than Dirac neutrinos - no vector currents

21. n, p Jm Z0 J= CAy(p’) Sy(p) p 0 Nuclear physics Nuclear spin n neutral current interactions n, p’ Neutrino current: Jm=y(p’)(CVgm-CAgmg5)y(p) Vector Axial- vector J0=CVy(p’)y(p) Dirac, scalar Dirac, Scalar Majorana Quark content

22. n neutral current interactions • Dirac neutrinos (Spin Independent, SI) • Cross section proportional to N2 (~1600 for Ge) • Independent of nuclear spin • Simple nuclear physics • Majorana neutrinos (Spin Dependent, SD) • No enhancement from coherence • Proportional to J(J+1) • Complicated nuclear physics, QCD • If a signal is observed, do not know if it is from SI or SD, sSI~N2sSD

23. Majorana neutrinos as relics Using limits on the flux from CDMS 2004… …density limit factor of 1000 worse… …No cosmological limit on Majorana neutrinos

24. Current state of play for SI interactions CDMS 2004 Lots of models

25. Where are we experimentally? • General focus on: • Dark matter • SUSY • Spin independent interactions Dark Matter recoil collaborations around the world

26. Candidate nuclei • Need nuclei with lots of spin (i.e. J large) • Few neutrons (as little SI interaction as possible) • Favorable nuclear physics (i.e. l large) • Favorable experimental conditions • No long lived isotopes • Sensitive to recoils (phonons) • Easy to purify, handle

27. A New Dark Matter Detector 1 m3 box filled with low pressure CF4, a scintillating gas, low pressure (20-40 T) Recoil nucleus (~ 1 mm) Amplification system - Gain of 103-104 WIMP

28. With different potentials on opposite sides of GEM, large gains due to electron amplification in high electric field in holes

29. Triple GEM (F. Murtas)Gain per GEM ~ 100

30. Bangs: detection of products from dark matter annihilation

31. g e+/e- p/p Fragmentation and decay q nDM q W+ W- nDM Typical processes:

32. Galprop - I. Moskolenko and A. Strong - cosmic ray propagation problem fit to all known data Not normalized! Green’s functions - expected flux on Earth for uniform monoenergetic source of electrons

33. Integrated positron signal above 8 GeV for 100 GeV (solid line) and 30 GeV (dotted line). The Earth is located at 8.5 kpc radius.

34. Charged particles follow magnetic field lines

35. Magnetic turbulence - average variation of magnetic field: Mean time between scattering from inhomogenieties:

36. 30 GeV electron: v=c, gives average velocity along field c/31/2 Electron lifetime determined by time to to propagate one Xo=65 g/cm2 in hydrogen 1 proton/cm3 in ISM Xo=1.3 x 1013 kpc to=45 My

37. Number of scatterings: N=to/ts Random walk diffusion distance Diffusion coefficient Advance each step RMS number of steps

38. e+/e- spectrum at Earth Propagation makes a mess! During 3 kpc transit, DM annihilation products go through ~1 Xo of material e+/e- spectrum at point of annihilation

39. What 200 GeV dark matter annihilation looks like after the galaxy gets through with it.

40. Charged particle spectrometers In ~10 GeV region: p:e-:e+ 103:10:0.1 p:p 103:0.1 High Energy Antimatter Telescope AMS-02

41. “Typical” signal - neutralino annihilation Moral - in cosmic rays everything looks like

42. This first problem is that the propagation (especially solar modulation) is not well understood… …the second is that HEAT runs out of sensitivity at ~50 GeV… Fit with background (smooth) normalization with signal (bump) gives 55 times higher relic density than observed

43. AMS-02 will just nail this Questions Why use e+/e++e-? Solar modulation not important above 10 GeV. Same signal appears in e-, so why not use e+, e-,… in combined fit? AMS-01 took LOTS of e- data (easy to ID, no p!) Why not look at that?

45. Preliminary AMS-01 electron selection: • Downward going • |Q|=1 from both tracker and TOF • Well fit track with 4 hits • Not docked to MIR, not over SAA • Good match between TOF and track Highest HEAT Datapoint AMS-01 MDR Heat MDR

46. First glance at AMS-01 data (backgrounds, resolution not well understood yet). Need to do a lot of work • Proton background • Efficiency • Propagation

47. Bumps and Bangs: Terrestrial and solar capture

48. E nDM E-DE Maximum when =1, E=DE Most efficient energy transfer

49. 24Mg 28Si 32S 16O 56Fe, 58Ni Capture rate for Earth

50. Capture rate for Sun is ~108 times higher. Since Sun is mostly protons, no peaks and no strong suppression for Majorana type DM Earth Sun (scaled by 5 108