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c Roland Lüscher
Imperial College Of Science, Technology and Medicine, Prince Consort Road, London, SW7 2BZ, UK
Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK
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cB Ahmed, A Bewick, D Davidge, JV Dawson, AS Howard, I Ivaniouchenkov, WG Jones, MK Joshi, V Lebedenko,I Liubarsky, R Lüscher, T J Sumner, J J Quenby
Blackett Laboratory, Imperial College of Science, Technology and Medicine, LondonGJ Alner, SP Hart, JD Lewin, RM Preece, JW Roberts, NJT Smith, PF Smith
Particle Physics Department, Rutherford Appleton Laboratory, Chilton, OxonMJ Carson, T Gamble, VA Kudryavtsev, TB Lawson, MJ Lehner, PK Lightfoot, JE McMillan,B Morgan, SM Pealing, M Robinson, NJC Spooner, DR Tovey
Department of Physics and Astronomy, University of SheffieldDB Cline, H Wang, Y Seo, M Atac, F Sergiampietri
Physics and Astronomy, UCLAP Picchi, F Pietropaolo
CERN/ICGF-CNR-Torino/INFN-PadovaJT White, J Gao
Department of Physics, Texas A&M UniversityU Cotti, M Reyes, L Villasenor
Institute of Phys. and Maths., UMSNH, Morelia, MexicoA Zepeda
Physics Department, CINVESTAV, Mexico CityCJ Hailey, WW Craig, M Sileo, P Graham, J Hong
Astrophysics, Columbia University
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cEvidence for dark matter Rotation curve of a spiral galaxy:
• Measured circular rotation velocities as a function ofradius.
• Contributions due to the observed disk and gas, andfrom the dark halo are also shown.
Cosmology•• All viable cosmological scenariosAll viable cosmological scenarios
involve CDMinvolve CDM•• Consens Consens that ~7% of cluster DM isthat ~7% of cluster DM is
baryonicbaryonic•• Halo sizes are larger - typically 200Halo sizes are larger - typically 200
kpckpc in spirals in spirals
Particle Physics•• “Natural” “Natural” SUSY models have minimumSUSY models have minimum
sspp ~10 ~10-10-10 pbpb•• SUSY predicts a WIMP: the SUSY predicts a WIMP: the neutralinoneutralino
excluded
prob
ably
exc
lude
d by
acc
el.
theoretically plausiblemass region
1 10 100 1000
1000
10
0.1
0.001
WIMP mass (proton masses)
events per kg per day
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cBoulby Boulby minemine (North Yorkshire, UK)
1100m undergroundin salt&potash mine
Low radioactivityrock
Low Rn level
JIF-bid to create newclean undergroundarea and surfacecontrol-room
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cMine Mine specificitiesspecificities::
10-13
10-11
10-9
10-7
10-5
10-3
10-1
0 1000 2000 3000 4000 5000 6000 7000 8000
Muon FluxNeutron Production
Muo
n Fl
ux (c
m-2s-1
) or N
eutro
n Pr
oduc
tion
(g-1
s-1)
Depth (mwe)
Bou
lbySoud
an
Gra
n Sa
sso
Kam
ioka
Frej
us
Mon
t Bla
nc
Sudb
ury
• µ flux attenuated by 10-6:
• Low radon levels ~5 Bqm-3
(comparable to LNGS)
• Background from surroundingrock:
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cUKDMC/BDMC underground facilities ...UKDMC/BDMC underground facilities ...
Existing areas
New area
50 m
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c
DirtyStores
8m
20m
ElectricDarkrm
Clean Room
Experimental Halls - partitioned as required
Mess/Change
Stores
Wshop
Drift AreaTransfer
Clean-off
20m
47m14m
8m
6m
Runningboards
… and surface building… and surface building
… underground building ...… underground building ...
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cWIMP DIRECT DETECTION
Expected featureless differentialnuclear recoil energy spectrum forstationary detector---> looks like e- background
•• Kinematics Kinematics
•• Observed spectrum Observed spectrum
Background rejection tools:
(1) Nuclear recoil discrimination(2) Directional signal
WIMPWIMPMD MT
dRdE R
= RoEor
e -ER/Eor
recoil energy
incident energy
kinematic factor = 4MDMT/(MD + MT)2
event rate per unit mass
total event rate (point like nucleus)
1 2 3 4 5 6 7 8 9 100
(Eor
/Ro)
*dR
(vE,v
esc)/
dER
E/(E0r)
0123456789
10
dRdE = Ro S(E) F2(E) I(A)
obs
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cWIMP-target interaction
Signal Channel DifferencesGe, Si
40keV Nuclear RecoilM¡ 200GeVv = 230km/s
WIMP
Scintillation Ionisation Phonon
+ -+ -
+ -+ -
Pulse Shape Differences
NaI, CsI, Xe Signal Channel Differences
Xe
Gamma ray(or beta decay)
40keV Electron Recoil
Different dE/dX, Range, etc.
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c
• Heavy nuclei (A~130), sensitive to spin-independent interactions(Isi~A2).
• Isotopes with large spin-dependent factors, Isd~0.3 for 129Xe(23Na in NaI or 73Ge in Ge ~0.1) ...… as well as easier enrichement.
• Scintillation in UV (λ=175 nm), low visible energy threshold.• Large quenching factor for Xe recoils g(A)>0.2 (I in NaI: g(A)=0.09,
Na: g(A)~0.3), low recoil energy threshold.• Low background• Scintillation properties enables Pulse-Shape Discrimination
(PSD) between background (electron recoil) and nuclear recoilevents.
• Interesting ionisation properties …• Scale up possibilities (up to 1 ton ?)
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Singlet/triplet ratiodiffers betweennuclear and electronrecoils
Recombination onlyrelevant for electronrecoils (=> τ~45ns)
Pulse Shape Analysis
Kubota, NIM 196 (1982), 101;Doke, NIMA 291 (1990) 617
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c
ZonEd Proportionalscintillation in LIquid
Noble gases
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cPreliminaryPreliminary
resultsresultsEnergy spectrumEnergy spectrum
~1 month of data~1 month of data
85Kr level: <10-17 atoms/atom(standard lab purity Xe used) 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
0 500 1000 1500 2000E (keV)
dE/dx (Emax)
dE/dx (Eav)
Z-I data
Doke parameters:h = 0.16, C = 0.51S2 = .0097/.00032
Scintillation light yield in ZEPLIN I vs.Doke’s empirical formula
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cMean Time DistributionsMean Time Distributions
0.00001
0.0001
0.001
0.01
0.1
1
1 10 100
puls e time cons tant (ns )
ComptonCalibration
0.00001
0.0001
0.001
0.01
0.1
1
1 10 100
puls e time cons tant ns
Am/BeCalibration
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 10 20 30 40
obs erved energy keV
neut
ron/
gam
ma
TC r
atio
Fits
t(exp)
t(70%)
t(av90%Ratio
(preliminary)(preliminary)
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cPreliminaryPreliminary
limitslimits
0.00001
0.0001
0.001
0.01
0.1
1 10 100
fitted time cons tant ns
datagamma ca lGD fit
0.00001
0.0001
0.001
0.01
0.1
1 10 100
fitted time cons tant ns
Data: 90 kg*day
Comparisonwith calibration
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cPreliminary limitsPreliminary limits
0.000001
0.00001
0.0001
0.001
1 10 100 1000 10000Mass Gev
WIM
P-N
ucle
on c
ross
sec
tion
pb90 kg days
Projected for 720 kg days
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c• Operating 6.5 kg Kr free (85Kr β emitter) LXe,
using PSD.• 99.5% enriched in 129Xe (spin-dependent
coupl.) -> inelastic scattering• Measured quenching factor ~ 45% - 65%.• Stable operation -105oC.
(Nuovo Cim 19 (1996) 537)
Other Xe detector: DAMA collaboration
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ce-
• Preventsrecombination
• Drifts e-
Nuclear recoil: high primary scintillation, low ionisation yield
Electron recoil: low primary scintillation, high ionisation yield
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cZeplinZeplin-2, a Double-Phase -2, a Double-Phase Xe Xe detectordetector
• Ionisation electron drift towards a high field region in thegas phase.
• Electroluminescence light from the avalanche process
UCLA/Torino/CERNtest chamber:
γ
Electro-luminescence
recoil
Activevolume(1kg LXe)
Gasphase
Primary-Scintillation
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cScintillation, ionisation yield
Free electron lifetime > 5msec
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c
90% nu.rec.<3% elec.rec.
@ 10keV
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Construction in progress -finished in a couple of month.
Commissioning and installationin Boulby this year
=> ~30kg detector, Zeplin-2:
UCLA, Torino, Padova, UKDMC
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Double-phase,high field
Prototype Chamber (ICSTM)
PM in LXe- Less noise- better light coll.
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c
6kg LXe
Zeplin-3: UKDMC,ITEP, Columbia
31 PMT
Construction started
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cOther Xe detector: Kamioka
• Liquid-gas double phase xenon• 0.3l low background construction• 8 cm drift to proportional scintillation
region• 99% background rejection for 10-100 keV• 3 months continuous operation, 1 kg target
Towards 1 ton?
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One possibility
… the way towards 1 TON ? … the way towards 1 TON ?ZeplinZeplin - MAX - MAX
Goal:(a) attain 0.0001/kg/d,
(b) diagnostic array with complementarytechniques
UCLA, Columbia, Texas A&M
UKDMC: Sheffield, ICSTM, RALEuropean:
US:ITEP, CERN/Padova, Torino, Coimbra
3 modules
80 kg target
4 sub- units
shielding
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cNew ideas?
• CsI photocathodes in LXe:E.Aprile, NIMA 338 (1994), 328; NIMA 343 (1994), 121. QE = 31%
May also be used as amplifier in Zeplin-2 (UCLA-TAMU)
• APD (avalanche photo-diodes)? (Coimbra)
HVLumines. plate
CsI
PMT
Xe gas
R&D for use in Lxe to be continued
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Liquid Xe
Xe Gas
HeCooling
GEMs
CsI
PTFEReflector
CsI
FieldShapingRings
• GEM phototubes in noble gases:http://gdd.web.cern.ch/GDD/A.Buzulutskov, NIMA, 443 (2000), 164.
• MicroMEGAS in noble gas?
(UK R&D):
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cSensitivity of a 1 ton Zeplin:
CDMS IICRESST II
NaI 1996 limit
Zeplin-1 now
Zeplin-1 (+8month)
Zeplin-2/-3
10-3
10-4
10-5
10-6
10-7
10-8
10-9
10-1010 100 1000 [GeV]
Zeplin-1ton
[pb]
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DAMA positive signal, PLB 2000;limits, PLB 1996;
CDMS at Stanford, PRL 2000;CRESST 2001;EDELWEISS 2001.