6 Nov 2012 ... Evidence (Astrophysical Detection). 2. Candidates ... 3. Direct Detection (Particle
Physics) ... D. H. Perkins, Particle Astrophysics (2004) ...
Dark Matter, Low-Background Physics RHUL Jocelyn Monroe
Nov. 6, 2012
1. Evidence (Astrophysical Detection) 2. Candidates, Properties 3. Direct Detection (Particle Physics)
1st Observation: 1930s
Fritz Zwicky
(Kitt Peak)
Virial Theorem: kinetic energy ∝ potential energy
implies 400x more mass than visible!
Vera Rubin
Confirmation: 1980s Rotation velocity v(r) of spiral galaxies
(M. Kamionkowski, astro-ph/9809214)
implies 100x more mass than visible!
WMAP Cosmic Microwave Background
WMAP
CMB Acoustic Spectrum
Baryons compress photon-baryon plasma at recombination, photons exert pressure, competition gives rise to pressure wave
D. H. Perkins, Particle Astrophysics (2004)
BBN
BBN
lines = predicted light element abundances vs. baryon density boxes = observed abundances (1, 2 sigma) vertical band = CMB measure of baryon density (PDG)
Bullet Cluster
(NASA/Chandra/Magellan/Hubble)
The Standard Model of Cosmology E. Komatsu et al., Astrophys. J. Suppl 192 (2011) 18
Dark Matter is ~23% of the universe.
HEPAP/AAAC DMSAG Subpanel (2007)
Dark Matter Candidates strong e.m. weak
interaction strengths
k uar t-q
on ctr ele
trin neu
masses
o?
gravity
Axions
WIMP Number Density
D. H. Perkins, Particle Astrophysics (2004)
WIMP Mass Range
D. H. Perkins, Particle Astrophysics (2004)
WIMP-Nucleon Scattering Event Rate Spin Independent: χscatters coherently off of the entire nucleus A: σ~A2 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!
Mχ = 100 GeV σSI = 1E-44 cm2
Direct Detection Experiments Signal: χN ➙χN’
χ
Sc int illa
χ
tio n
Heat
Ion i
zat ion
Backgrounds: n N ➙ n N’ γ e- ➙ γ e-’ N ➙ N’ + α, eν N ➙ ν N’
DRIFT IGEX ArDM
WARP ZeplinIII
Xenon100 LUX
Newage Ioniz
Picasso COUPP
ation !
CoGeNT
DMTPC ANaIS DEAP/CLEAN XMASS
CDMS Edelweiss
Heat
!
n! o i t a l l Scinti
KIMS CRESST
Dama/LIBRA CRESSTII ROSEBUD
Backgrounds 10,000 events
photon scattering background
In dark matter experiments...
?
10,000 events
? 1,000 events
N
Anything else that does this can fake a dark matter signal!
100 events
1 event
radon decay background
neutron scattering background
neutrino scattering background
smallest dark matter scattering signal?
EM Backgrounds (D. McKinsey)
Gamma ray interaction rate is proportional to (# of electrons in detector) x (gamma ray flux) Typical count rate = 100 events/s/kg = 10,000,000 events/day/kg in a good lead shield, rate drops to 100 events/day/kg Best dark matter detectors: sensitive to 0.01 events/day/kg (σ~1E-44 cm2)
U and Th Decay Backgrounds can’t shield a detector from U and Th inside, recoiling progeny and associated betas can fake nuclear recoils
Neutron Backgrounds μ
γ
N
μ N* n
Cosmic muons spall neutrons: ~10-4 neutrons/ (100 GeV μ)/ gm/cm2 neutron flux: 10-8 - 10-10/cm2/s (range for depth)
D.-M. Mei, A. Hime, PRD73:053004 (2006)
eg. Study for CDMS-II Detector
ν Backgrounds can’t shield a detector from coherent elastic scattering of solar neutrinos
Φ(B8)
ν
ν Z
= 5.86 x 106 cm-2 s-1 N
N
100 events/ton-year = ~ 10-46 cm2 limit unless you measure the direction! JM, P. Fisher, PRD76:033007 (2007)
Backgrounds 10,000 events
10,000 events
the best experiments are here
1,000 events
100 events
1 event
Jocelyn Monroe
photon scattering background
radon decay background
neutron scattering background
neutrino scattering background
smallest dark matter scattering signal? October 13, 2012
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:0907.1438v1
arXiv:0912.3592v1 h+
Detector re-design a la EDELWEISS to reduce surface backgrounds x104
e-
0V
Charge side: 2 concentric electrodes (inner & outer) energy (& veto)
3” (7.6
1 cm
Ge: 250 g Si: 100 g
Ionization/Phonon yield vs. Erecoil (keV)
Xenon100
(S1)
Two-Phase liquid Xenon TPC, operated in LNGS
(S2) S1 [PE] 5
10
15
20
25
30
35
0.4
arXiv: 1104.2549v2
10
log (S2/S1)-ER mean
0.2
“S2”: primary scintillation “S1”: amplified, drifted ionization signal both read out with PMTs
0 -0.2 -0.4 -0.6 -0.8 -1 -1.2
(E. Aprile)
10
20
30
Energy [keVnr]
40
50
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)
Experimental Procedure
theorist: el what mod is h t s n i a l p x e rate?
3. measure event parameters in WIMP search data set
see a or se signal 4. blind analysis: open the box! t a li mit?
experimentalist:
5. measure number of events
The Low Background Frontier limit, :;
:;
:;
:;
Many Results Here, excludes regionshown Onlythis 2 strongest
&* % & &'()
%&
allowed region!
# "#$
!=
:;
:
.
:; . !"#$%#&''%()*+,- /
Complementary with High-Energy Frontier
8σ, inconsistent with many expts CoGeNT: 442 days, 0.5-3.0 keVee
CoGeNT (dashed line)
42 days
140
120
100
DAMA (solid line)
80
60
0
100
200
300
400
500
Days Since Dec 3, 2009
Annual Modulation June-December event rate asymmetry ~2-10% Drukier, Freese, Spergel, Phys. Rev. D33:3495 (1986)
Eur. Phys. J. C56:333-355 (2008)
BUT... CDMS modulation search not consistent with CoGeNT or DAMA/Libra (98.3% CL) arXiv:1203.1309
Events/30 days
DAMA/Libra positive result, >8σ, inconsistent with many expts CoGeNT: 442 days, 0.5-3.0 keVee
42 days
140
120
CoGeNT (dashed line)
100
80
60
0
100
200
300
400
CDMS (solid points) 500
Days Since Dec 3, 2009
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 Unambiguous proof: Correlation of WIMP-induced nuclear recoil signal with galactic motion
astro-ph/0609115
Events /kg / day
Directional Detection
0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 Re 0 20 1 coi 40 0.8 0.6 l K 6080 ine 100 0.20.4 !LAB ) tic 120 0 -0.2 En 140 os( C -0.4 erg 160 y (k180200 -1-0.8-0.6 eV )
Daily direction modulation: asymmetry ~ 20-100% in forward-backward event rate. Spergel, Phys. Rev. D36:1353 (1988)
recoili ng nucleu s
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, 021012 (2007)
DMTPC: in WIPP (US) CCD readout D. Dujmic, et al., NIM A 584:337 (2008)
NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (2010)
DMTPC limit (surface, 38 gm-day) S. Ahlen et al., Phys. Lett. B 695 (2011)
!p (cm2)
Spin-Dependent Cross Section: Latest Experiment Results -32 10-32 10
directional searches
DMTPC 10L surface -34
-34 10-34 10
-36 10-36 10
DRIFT sensitivity, Astropart.Phys. 25 (2012) 397
DMTPC, 10L sensitivity at WIPP
-38 10-38 10
-40 -40
10 10
cMSSM theory
1022 10
3
1033 10
WIMP mass mass (GeV) (GeV) WIMP Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001) 065016
NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (2010)
DMTPC limit (surface, 38 gm-day) S. Ahlen et al., Phys. Lett. B 695 (2011)
!p (cm2)
Spin-Dependent Cross Section: Latest Experiment Results 10-32 DMTPC 10L surface
directional searches DRIFT sensitivity,
10-34
Astropart.Phys. 25 (2012) 397
10-36
1D results COUPP PRL.106, 021303 (2011)
-38
10
SIMPLE
arXiv:1106.3014
10-40
PICASSO
cMSSM theory
102
arXiv:1202.1240
103
WIMP mass (GeV) Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001) 065016
NEWAGE limit (Kamioka) K. Miuchi et al., Phys.Lett.B686:11-17 (2010)
DMTPC limit (surface, 38 gm-day) S. Ahlen et al., Phys. Lett. B 695 (2011)
!p (cm2)
Spin-Dependent Cross Section: Latest Experiment Results 10-32
directional searches
DMTPC 10L surface
10-34
DRIFT sensitivity, Astropart.Phys. 25 (2012) 397
10-36
1D results COUPP PRL.106, 021303 (2011)
10-38
SIMPLE
arXiv:1106.3014
1m3
at WIPP (DMTPCino) projected sensitivity
-40
10
Theory region: Rozkowski et al JHEP 07 (2007) 075 Ellis et al PRD63 (2001) 065016
PICASSO
cMSSM theory 2
10
arXiv:1202.1240
3
10
WIMP mass (GeV)
Global SI Dark Matter Programme, Sensitivity Reach
Proposed Being designed Under construction/in operation
results: 2012
Current results
10-2
10-1
102 1 10 -46 Spin-independent sensitivity (x10 cm2)
NB: projected sensitivities (all except green) assume zero background.
future present
LZ CLEAN EURECA Stage-II SuperCDMS-100 XENON-1T DEAP-3600 LUX EDELWEISS III miniCLEAN XMASS COUPP-60 SuperCDMS-10 Xenon-100 ZEPLIN III EDELWEISS II CDMS II
completed
2016
2018
CYGNUS (Directional)
Backup Slides
Setting a Limit 1. The theoretical dark matter interaction rate is: dR = dER
�
� � � c1 R0 −c2 ER exp E0 r E0 r
ER = nuclear recoil energy, E0 = dark matter particle energy
2. Experiments measure: R0 =
��
2v0 √ π
��
�� N0 (ρD /mD ) σ0 × exposure A
σA = σ0 F 2 (ER , A)Ic ,
F 2 (ER , A) = nuclear f orm f actor,
Ic = A2
3. vary σA until (90% of the time) theory predicts observed rate 4. Normalize to σW −N to compare limits: σW −N = Jocelyn Monroe
�
�2 � �2 µ1 1 σA µA A
mD mtarget µ = (mD + mtarget ) October 31, 2007
... in the Presence of Background step 3: vary σA until (90% of the time) theory predicts observed maximum gap between background events S. Yellin, Phys. Rev. D66:032005 (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
Savage et al., arXiv:0808.3607
SI vs. SD
(nuclear form factor)
Ellis et al., arXiv:0808.3607
Nuclear physics uncertainties are important!
Scale Parameters
SN1A Data
