Dark Matter, Low-Background Physics

Transcription

1 Dark Matter, Low-Background Physics RHUL Jocelyn Monroe Nov. 6, 2012

2 1. Evidence (Astrophysical Detection) 2. Candidates, Properties 3. Direct Detection (Particle Physics)

3 1 st Observation: 1930s Fritz Zwicky (Kitt Peak) Virial Theorem: kinetic energy potential energy implies 400x more mass than visible!

4 Confirmation: 1980s Vera Rubin Rotation velocity v(r) of spiral galaxies (M. Kamionkowski, astro-ph/ ) implies 0x more mass than visible!

5

6 WMAP Cosmic Microwave Background WMAP

7 CMB Acoustic Spectrum Baryons compress photon-baryon plasma at recombination, photons exert pressure, competition gives rise to pressure wave

8 BBN D. H. Perkins, Particle Astrophysics (2004)

9 BBN lines = predicted light element abundances vs. baryon density boxes = observed abundances (1, 2 sigma) vertical band = CMB measure of baryon density (PDG)

10 Bullet Cluster (NASA/Chandra/Magellan/Hubble)

11 The Standard Model of Cosmology E. Komatsu et al., Astrophys. J. Suppl 192 (2011) 18 Dark Matter is ~23% of the universe.

12 Dark Matter Candidates interaction strengths strong e.m. weak HEPAP/AAAC DMSAG Subpanel (2007) gravity masses neutrino? electron t-quark

13 Axions

14 WIMP Number Density D. H. Perkins, Particle Astrophysics (2004)

15 WIMP Mass Range D. H. Perkins, Particle Astrophysics (2004)

16

17 WIMP-Nucleon Scattering Event Rate Spin Independent: scatters coherently off of the entire nucleus A: σ~a 2 D. Z. Freedman, PRD 9, 1389 (1974) Spin Dependent: only unpaired nucleons contribute to scattering amplitude: σ~ J(J+1) kinematics: v/c ~ 1E-3! M χ = 0 GeV σ SI = 1E-44 cm 2

18 Ionization Direct Detection Experiments Signal: χn χn χ Scintillation χ Heat Backgrounds: n N n N γ e - γ e - N N + α, e - ν N ν N

19 DRIFT ArDM Xenon0 LUX WARP ZeplinIII IGEX Newage Ionization! Picasso COUPP CDMS Edelweiss CoGeNT DMTPC Heat! DEAP/CLEAN XMASS ANaIS Scintillation! KIMS Dama/LIBRA CRESST CRESSTII ROSEBUD

20 Backgrounds In dark matter experiments... N photon,000 scattering events background radon,000 decay events background neutron 1,000 scattering events background Anything else that does this can fake a dark matter signal! neutrino 0 scattering events background 1 event smallest dark matter scattering signal?

21 EM Backgrounds (D. McKinsey) Gamma ray interaction rate is proportional to (# of electrons in detector) x (gamma ray flux) Typical count rate = 0 events/s/kg =,000,000 events/day/kg in a good lead shield, rate drops to 0 events/day/kg Best dark matter detectors: sensitive to 0.01 events/day/kg (σ~1e-44 cm 2 )

22 U and Th Decay Backgrounds can t shield a detector from U and Th inside, recoiling progeny and associated betas can fake nuclear recoils

23 Neutron Backgrounds μ N γ Cosmic muons spall neutrons: ~ -4 neutrons/ (0 GeV μ)/ gm/cm 2 μ N* n D.-M. Mei, A. Hime, PRD73: (2006) eg. Study for CDMS-II Detector neutron flux: /cm 2 /s (range for depth)

24 ν Backgrounds can t shield a detector from coherent elastic scattering of solar neutrinos Φ(B 8 ) = 5.86 x 6 cm -2 s -1 ν Z ν N N 0 events/ton-year = ~ -46 cm 2 limit unless you measure the direction! JM, P. Fisher, PRD76: (2007)

25 Backgrounds photon,000 scattering events background the best experiments are here radon,000 decay events background neutron 1,000 scattering events background neutrino 0 scattering events background 1 event smallest dark matter scattering signal? Jocelyn Monroe October 13, 2012

26 CDMS (material thanks to E. Figuroa) Phonon side: 4 quadrants of phonon sensors for energy & position (timing) -3V Transition Edge Sensors, operated at ~40 mk on Ge and Si crystals, in Soudan arxiv: v1 arxiv: v1 0V h + e - Detector re-design a la EDELWEISS to reduce surface backgrounds x 4 Charge side: 2 concentric electrodes (inner & outer) energy (& veto) 3 (7.6 1 cm Ge: 250 g Si: 0 g Ionization/Phonon yield vs. E recoil (kev)

27 Xenon0 (S1) Two-Phase liquid Xenon TPC, operated in LNGS (S2) S1 [PE] arxiv: v2 log (S2/S1)-ER mean 0.2 S2 : primary scintillation S1 : amplified, drifted ionization signal both read out with PMTs (E. Aprile) Energy [kevnr] 40 50

28 Experimental Procedure 1. using calibration data, define background and signal regions 2. using calibration data, define a region with zero expected background events nuclear recoil energy (any events in the blind region are signal candidates)

29 Experimental Procedure theorist: what model explains this rate? see a signal or set a limit? 3. measure event parameters in WIMP search data set 4. blind analysis: open the box! experimentalist: 5. measure number of events

30 The Low Background Frontier Scalability of Detector Technology 0"%!"#$!12-3*41%564''%0*-7841%(-9. / :;!=. :;!=< :;!== :;!=@ :;!=? :;!=> Many Results Here, Only 2 strongest shown limit, excludes this region allowed region Dark Matter!"#$#%&&'()&%&* +,-.'()&%&*!"#$#%&&'()&%%* Direct Detection Parameter Space -/0/+1"2# 13! +1"2#7'#=,"24!56&& +1"2#7'089:;8<'2; +1"2#7'>=?<=9=>'2; :; : :;. :; <!"#$%#&''%()*+,-. / Complementary with High-Energy Frontier 1 event/ kg/day 1 event/ 0 kg/day 1 event/ 0 kg/ 0 days need 0-00 dark matter events to measure mass, cross section New Techniques for Backgrounds

31 Spin-Independent Cross Section: Latest Experiment Results E. Aprile et al., arxiv: event/ kg/day 1 event/ 0 kg/day tonne-scale detectors likely required for discovery

32 Spin-Independent Cross Section: Latest Theory Results O. Buchmuller et al., arxiv: We are Here We are Here CAVEAT: many more exotic models (Asymmetric DM, Dark Forces Models, Magnetic Inelastic DM, Sterile Nus + Freeze-In, Isospin-Violating DM, Emergent DM and L# models...

33 3 is a lot of σ -24 cm 2 : σ(neutron-a elastic scattering) -28 cm 2 : σ(total inelastic pp at TeVatron) Not to Scale -35 cm 2 : σ(gg H) at LHC (Standard Model) -39 cm 2 : σ(single top) at TeVatron -40 cm 2 : σ(ν QE) at MINOS -45 cm 2 : σ(ν-e Elastic) for solar ν σ(dm coherent scattering)? -48 cm 2

34 Direct Dark Matter Signals? DAMA/Libra COGENT arxiv: N Z N CRESST-II arxiv: CDMS arxiv: v1 arxiv: dark matter? backgrounds?

35 Indirect Dark Matter Signals? PAMELA arxiv: ? Fermi LAT arxiv: ATIC dark matter? local astrophysics?

36 Annual Modulation June-December event rate asymmetry ~2-% Drukier, Freese, Spergel, Phys. Rev. D33:3495 (1986) Eur. Phys. J. C56: (2008) DAMA/Libra positive result, >8σ, inconsistent with many expts CoGeNT modulation result, 2.8σ, ~consistent with DAMA/Libra J. Collar, STSI (2011), arxiv: v1 Events/30 days CoGeNT: 442 days, kev ee 42 days Days Since Dec 3, 2009 CoGeNT (dashed line) DAMA (solid line)

37 Annual Modulation June-December event rate asymmetry ~2-% Drukier, Freese, Spergel, Phys. Rev. D33:3495 (1986) Eur. Phys. J. C56: (2008) DAMA/Libra positive result, >8σ, inconsistent with many expts BUT... CDMS modulation search not consistent with CoGeNT or DAMA/Libra (98.3% CL) arxiv: Events/30 days CoGeNT: 442 days, kev ee 42 days Days Since Dec 3, 2009 CoGeNT (dashed line) CDMS (solid points)

38 Directional Detection The Dark Matter Wind blows from Cygnus search for a dark matter source Simulated Dark Matter Sky Map simulated reconstructed dark matter sky map: search for anisotropy astro-ph/ Unambiguous proof: Correlation of WIMP-induced nuclear recoil signal with galactic motion

39 Directional Detection Events /kg / day Recoil Kinetic Energy (kev) Cos(! LAB ) recoiling nucleus Daily direction modulation: asymmetry ~ 20-0% in forward-backward event rate. Spergel, Phys. Rev. D36:1353 (1988)

40 Directionality Around the World DRIFT: in Boulby (UK) S. Burgos et al., Astropart. Phys. 28, 409 (2007) NEWAGE: in Kamioka (JP), first directional dark matter limit! K. Miuchi, et al., Phys.Lett.B654:58-64 (2007) MiMAC-He3: ILL/Modane (FR) D. Santos, et al., J. Phys. Conf. Ser. 65, 0212 (2007) DMTPC: in WIPP (US) CCD readout D. Dujmic, et al., NIM A 584:337 (2008)

41 Spin-Dependent Cross Section: Latest Experiment Results 2 ) (cm 2 2 ) (cm ) (cm NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (20) DMTPC limit (surface, 38 gm-day)! p! p! p DMTPC L surface DMTPC, L sensitivity at WIPP directional searches DRIFT sensitivity, Astropart.Phys. 25 (2012) 397 S. Ahlen et al., Phys. Lett. B 695 (2011) cmssm theory 2 3 WIMP mass (GeV) Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001)

42 Spin-Dependent Cross Section: Latest Experiment Results 2 ) (cm NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (20) DMTPC limit (surface, 38 gm-day) S. Ahlen et al., Phys. Lett. B 695 (2011)! p cmssm theory 2 DMTPC L surface 3 directional searches DRIFT sensitivity, Astropart.Phys. 25 (2012) 397 1D results COUPP PRL.6, (2011) SIMPLE arxiv: PICASSO arxiv: WIMP mass (GeV) Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001)

43 Spin-Dependent Cross Section: Latest Experiment Results 2 ) (cm NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (20) DMTPC limit (surface, 38 gm-day) S. Ahlen et al., Phys. Lett. B 695 (2011) 1m 3 at WIPP (DMTPCino) projected sensitivity! p cmssm theory 2 DMTPC L surface 3 WIMP mass (GeV) directional searches DRIFT sensitivity, Astropart.Phys. 25 (2012) 397 1D results COUPP PRL.6, (2011) SIMPLE arxiv: PICASSO arxiv: Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001)

44 Global SI Dark Matter Programme, Sensitivity Reach results: Proposed Being designed Under construction/in operation Current results -1 CYGNUS (Directional) LZ CLEAN EURECA Stage-II SuperCDMS-0 XENON-1T DEAP-3600 LUX EDELWEISS III miniclean XMASS COUPP-60 SuperCDMS- Xenon-0 ZEPLIN III EDELWEISS II CDMS II 1 Spin-independent sensitivity (x 2-46 cm 2 ) completed present future NB: projected sensitivities (all except green) assume zero background.

45 Backup Slides

46 Setting a Limit 1. The theoretical dark matter interaction rate is: dr de R = c1 R 0 E 0 r c2 E R exp E 0 r E R = nuclear recoil energy, E 0 = dark matter particle energy 2. Experiments measure: R 0 = 2v0 π N0 (ρ D /m D ) A σ 0 exposure σ A = σ 0 F 2 (E R,A)I c, F 2 (E I c = A 2 R,A) =nuclear f orm f actor, 3. vary σ A until (90% of the time) theory predicts observed rate σ W N = µ1 σ W N σ A A 4. Normalize to to compare limits: µ A µ = m D m target (m D + m target ) Jocelyn Monroe October 31, 2007

47 ... in the Presence of Background σ A step 3: vary until (90% of the time) theory predicts observed maximum gap between background events S. Yellin, Phys. Rev. D66: (2002) Yellin gap method: a way to make a zero-background measurement over a restricted range of an experiment s acceptance (zero signal too) Jocelyn Monroe October 31, 2007

48 SI vs. SD Savage et al., arxiv: (nuclear form factor) Ellis et al., arxiv: Nuclear physics uncertainties are important!

49 Scale Parameters

50 SN1A Data