Chapter 12. Dark Matter

Transcription

1 Karl-Heinz Kampert Univ. Wuppertal 128 Chapter 12 Dark Matter

2 Karl-Heinz Kampert Univ. Wuppertal Baryonic Dark Matter Brightness & Rotation Curve of NGC3198 Brightness Rotation Curve measured expected from mass associated with light profile

3 Karl-Heinz Kampert Univ. Wuppertal 130 NGC 7331 astro-ph/ observed radial velocities based on Doppler effect rotation curve with individual contributions fit of major axis Note: Here we assume applicability of Newtonian laws far beyond solar system, i.e. the region of proven correctness. (Discussed alternative: MOdified Newtoanian Dynamics; MOND)

4 Karl-Heinz Kampert Univ. Wuppertal 131 Gravitational Lens

5 Karl-Heinz Kampert Univ. Wuppertal 132 Lense in foreground Einstein Ring Lensed Object (in background)

6 Karl-Heinz Kampert Univ. Wuppertal 133 Einstein Ring

7 Karl-Heinz Kampert Univ. Wuppertal Microlensed LMC Objects Massive Compact Halo Objects (MACHO) light from some star in LMC Sun typically separated by milli-arc-sec (not resolved) But: amplification of light if images are not resolved: t 100 days M MACHO M up to ~ 0.75 m

8 Observations JD! Fig. 8. The EROS-2 light curve of EROS-1 microlensing candidate years after the variation observed in EROS-1. Also shown is the co P. Tisserand et al.: Limits on the Macho content of excursion of the thegalactic event. Halo from Eros EROS2!SMC! R u0 te t0 R B u0 te t0 B lm0553n R u te R t B u0 te B t MACHO!LMC! R R B B ~ 140 days JD! ! R eros astro-ph/ sm0054m R eros 10 ~ 34 days (B!R)eros JD! !0.5-7 MACHOS as the major component of Galactic DM over 10 MMACHO < 5 shown can be ruled Sun Also Fig. 6. The light curves of EROS-2 microlensing candidatefig. EROS2-SMC-1 (star<light sm005-4m-5761). is the color9. The EROS-2 curve /M of MACHO microlensing candidat out, i.e. below magnitude diagram of the star s CCD-quadrant and fraction the excursion of the event. 6.8well years after the10% variation seen by MACHO. Also shown is the co Karl-Heinz Kampert Univ. Wuppertal excursion of the event. 135

9 Karl-Heinz Kampert Univ. Wuppertal 136 Intra-Cluster Gas X-ray surveys of galaxy clusters allow also to estimate ΩM Surface brightness ρ, T profiles of Gas Mass Result: More matter contained in hot gas than in stars

10 Karl-Heinz Kampert Univ. Wuppertal 137 Non-Baryonic DM Expect ~ 0.25 Ωcrit Classical candidate: Neutrinos (note: 350 νs / cm 3!) If massive, could contribute significantly to DM Ω ν h 2 = i m ν i 93 ev t 3 He + β + ν e mν < 2.05 ev Ων < 0.07 Since mν is very small, velocity would be high, thus we call them Hot Dark Matter (HDM) Non-relativistic particles with masses in GeV scale are called Cold Dark Matter (CDM)

11 Karl-Heinz Kampert Univ. Wuppertal 138 AXIONs HDM candidate (light pseudoscalar particle; J P = 0 - ) (proposed because of absence of CP violation in strong interaction) Weak interaction: 1/mA 5 > tuniverse for ma < 10 ev expect ma in range ev/c 2 expect abundance of /cm 3 May be observed by interaction with strong B-fields B-field Axion -ray Sun Axion LHC magnet + X-ray detect. CAST CERN

12 WIMPs Weakly Interacting Massive Particle (generally preferred candidate) May be detected directly by elastic WIMP-nucleus scattering; recoil of nucleus then detected by ionisation a/o by phonons Highly sensitive semi-conductor counters may be used or bolometers at cryogenic temperatures (T < 1 K) T = E recoil V c V (T ) mx mt E recoil = m T m X (m T + m X ) 2 m Xv 2 (1 cosθ) c V = Q T ( T θ D ) 3 G(T) θ WIMP example: V= 1 cm 3 Si crystal; Erecoil = 6 kev ΔT = 10-5 K; can be measured Karl-Heinz Kampert Univ. Wuppertal 139 T 0 Temperature sensor E Absorber C(T)

13 Karl-Heinz Kampert Univ. Wuppertal Direct detection techniques CDMS EDELWEISS Phonons CRESST E R Charge Light ZEPLIN, XENON XMASS, WARP, ArDM

14 Karl-Heinz Kampert Univ. Wuppertal 141 WIMPs Expected event rate R: R = N T φ(e) σ(e)de # of target atoms flux of DM particles cross section Typical rates: events/day/kg ~ Thus, background is the problem! 30 km/s Possible signature by velocity of Earth around Sun (seasonal modulation)

15 The DAMA experiment At LNGS (3800 mwe) 9 x 9.7 kg low activity NaI crystals, each viewed by 2 PMs (5-7 pe/kev) QF on I: 8% background level: 1-2 events/kg/d/kev E threshold! 2 kev e! 25 kev r End of data taking 2002 PSD: statistical analysis of pulse time constant => limit from 1996 Nuclear recoils Electron recoils 100 ns 500 ns PLB 509 (2001) Karl-Heinz Kampert Univ. Wuppertal

16 The DAMA Signal astro-ph/ , Riv. N. Cim. 26, 2003 A cos [#(t-t 0 )]; t 0 = d; T = 1yr Annual modulation analysis: -> 7 annual cycles: kg x days -> positive signal (6.3! CL) Studied variations of: Day 1 = Jan 1, 1995; A = / c/d/kg/kev T, P(N 2 ), radon, noise, energy scale, efficiencies, n-background, "-background A = / ev/d/kg/kev A = / ev/d/kg/kev Karl-Heinz Kampert Univ. Wuppertal

17 CDMS detectors I bias SQUID array R bias D C A B R feedback Phonon D Absorber: 250 g Ge or 100 g Si crystal 1 cm thick x 7.5 cm diameter T-sensor: photolithographic patterned thin Al+W films V qbias Q outer Q inner passive tungsten grid Measure ionization in low-field (~volts/cm) with segmented contacts to allow rejection of events near outer edge 4144 (4 x 1036) QETs 250!m x 1!m W (35 nm thick) 380! x 60! aluminum fins (300 nm thick) Karl-Heinz Kampert Univ. Wuppertal

18 CDMS Background Discrimination Use phonon risetime and charge to phonon delay for discrimination of surface events ( betas ) Ionization yield alone:! Ionization+phonon timing:! Rejects >99.9% of gammas, >75% of betas Rejects > % of gammas, >99% of betas Phonon delay [µs] neutrons gammas Amplitude Ionization Yield surface events phonon delay Time [µs] Karl-Heinz Kampert Univ. Wuppertal

19 Karl-Heinz Kampert Univ. Wuppertal Where do we stand? ~ 0.2 event/kg/day 1998 Most advanced experiments start to test the predicted SUSY parameter space One evidence for a positive WIMP signal 2006 Not confirmed by other experiments

20 Karl-Heinz Kampert Univ. Wuppertal 147 Indirect Measurement WIMP capture in the sun! and annihilation in neutrinos " # n DETECT! +!! W + W! " + " Preferred: Neutralino, the Lightest SUSY-particle

21 Karl-Heinz Kampert Univ. Wuppertal WIMP search PRELIMINARY!"#"$%&'(&#)'( *+),&*-'#&./-$0!"#"$%&'(&#)'( *+),&*-'#&1)(!"#$%&'()*+,-++ *"()./+#)%(.0+ 12! ? <3<=!<+7- <>/%()# :+-)%(# 789 :+ 15.)2;,)6

22 Karl-Heinz Kampert Univ. Wuppertal 149 Hints from Large Scale Structure Hints from Large Scale Structure

23 Karl-Heinz Kampert Univ. Wuppertal 150 Large Scale Structure: Simulations!"#$%&'!&(&)"'*+,-$.&/'#0/#, 1#0/20-2$3456$ /7-$345 8"(#,2$3456$ /9: ;<,/$3456$!9: