the xenon dark matter experiment
DESCRIPTION
The XENON Dark Matter Experiment. Elena Aprile Physics Department and Columbia Astrophysics Laboratory Columbia University http:// www.astro.columbia.edu/~lxe/XENON/. Dark Energy 73%. Energy 2/3. The Case for Non-Baryonic Dark Matter Conclusion from all Evidence. - PowerPoint PPT PresentationTRANSCRIPT
The XENON Dark Matter Experiment
Elena Aprile
Physics Department and Columbia Astrophysics Laboratory
Columbia University
http://www.astro.columbia.edu/~lxe/XENON/
Energy 2/3
Dark Energy 73%
The Case for Non-Baryonic Dark MatterConclusion from all Evidence
Total = 1 = 2/3m = 1/3
>95% of the Universe composition still unidentified.
ΩΩmm >> Ω >> ΩbbWhat is this Dark Matter?
Non-baryonic Cold Dark Matter Candidates
✦ LSP (neutralino)
✦ LKP (lightest Kaluza-Klein)
✦ Axions
✦ Solitons
✦ Wimpzillas, ..
✦ Different mass range and interaction rate..
Must be stable, weakly interacting and with right relic density WIMPs
ANTARES
LHC
Cold Dark Matter Relics can be..
• Produced and detected at accelerators
• Indirectly detected via their Annihilation in Sun, Earth, Galaxy Neutrinos,positrons, antiprotons, -rays
GLASTAMS
AMANDA/ICECUBE
…or can be directly detected in terrestrial detectors
WIMPs scatter elastically with nuclei:
Rate ~ N m <>
N = number of target nuclei in detector
= local WIMP density
<> = scattering cross section
From the density of dark matter in the galaxy:
Every liter of space: 10-100 WIMPs, moving at 1/1000 the speed of light
=> Less than 1 WIMP/week will collide with an atom in 1kg material
WIMP
WIMP
Direct Detection:a challenging task
Rate: 10-1 - 10-5 /kg/day
Nuclear recoil energy: 10 - 100 keV
Very large background: gamma rays and neutrons from radioactivity and cosmic rays
Detectors must effectively discriminate between Nuclear Recoils (Neutrons, WIMPs) Electron Recoils (gammas, betas)
recoil energy
Light
Charge Heat
CDMS, EDELWEISS
CRESSTZEPLINXMASSXENONWARP
World Wide WIMP Search
Picasso
CDMS I
LiFElegant V&VI
CsI
IGEX
Gran SassoDAMA/LIBRACRESST WARPXENONCUORE
CanFrancIGEXROSEBUDANAISArDM
EDELWEISS I/II
BoulbyZEPLIN I/II/III/MAXDRIFT
x XMASSKIMS
MajoranaSuperCDMSCLEAN
ORPHEUS
CDMS II
• Modular design: 1 ton active Xe distributed in an array of ten 3D position sensitive dual-phase (liquid/gas) XeTPCs, actively shielded by a LXe veto.
• Simultaneous detection of ionization and scintillation for event-by-event discrimination of nuclear recoils from electron recoils (>99.5%) down to 16 keVr.
• XENON funded by NSF and DOE.
• Phase1 (XENON10) : 15 kg detector has been installed in Gran Sasso Lab ( equipment arrived on March 7, 2006). Shield construction to be completed by May 15, 2006. XENON10 physics run (June-Aug, 2006) will determine design of 1st 100 kg module
• Phase2 (XENON100): Goal is data taking by late 2007. After 3 months at a background < 1x10-4 cts/keV/kg/day after rejection, the sensitivity of XENON100 would be ~2x10-45 cm2 .
The XENON Experiment: Overview
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Columbia University Elena Aprile (PI), Karl-Ludwig Giboni, Sharmila Kamat,
Maria Elena Monzani, Kaixuan Ni*, Guillaume Plante*, and Masaki YamashitaBrown University
Richard Gaitskell, Simon Fiorucci, Peter Sorensen*, Luiz DeViveiros*University of Florida
Laura Baudis, Jesse Angle*, Joerg Orboeck, Aaron Manalaysay* Lawrence Livermore National Laboratory
Adam Bernstein, Chris Hagmann, Norm Madden and Celeste WinantCase Western Reserve University
Tom Shutt, Eric Dahl*, John Kwong* and Alexander BolozdynyaRice University
Uwe Oberlack , Roman Gomez* and Peter ShaginYale University
Daniel McKinsey, Richard Hasty, Angel Manzur*LNGS
Francesco Arneodo, Alfredo Ferella*Coimbra University
Jose Matias Lopes, Joaquin Santos
The XENON Collaboration
XENON Dark Matter Goals
SUSY TheoryModels
Dark Matter Data Plotterhttp://dmtools.brown.edu
CDMS II goal
SUSY TheoryModels
•XENON10 (2006-2007):
10 kg target ~2 events/10kg/month
Equivalent CDMSII Goal for mass >100 GeV (Current CDMS limit is 10 x above this level)
Important goal of XENON10 underground is to establish performance of dual phase TPC to design optimized XENON100
•XENON100 (2007-2008):
100 kg target ~2 events/100kg/month
•XENON-1T (2008-2012?):
1 ton (10 x 100 kg modules)
10-46 cm2 or ~1 event/1 tonne/month
Test majority of SUSY models. Discover Dark Matter!
Why Liquid Xenon?High atomic mass (A ~ 131): favorable for SI case ( ~ A2)
Odd isotope with large SD enhancement factors (129Xe, 131Xe)
High atomic number (Z=54) and density (3g/cm3) => compact, self-shielding geometry
‘Easy’ cryogenics at -100 C
No long-lived radioisotopes
Excellent Scintillator (~NaI(Tl)) and Efficient Ionizer (W=15.6 eV)
Simultaneous Light and Charge Detection => background discrimination
Xe Eth=16 keVr gives 0.1 event/kg/day (30% of zero thresh. sig.)
Very Typical WIMP Signal in Xe
Xe rate enhanced by high A, but low threshold necessary to avoid form factor suppression
Principle of OperationWIMP or Neutronnuclear
recoil
electronrecoil
Gamma or Electron
Fast Slow
Kubota et al. 1979, Phys. Rev.B
Ionization & Scintillation in LXe
.
7 10 15 20
photon energy [eV]
200 150 100
wavelength [nm]
liquid
solid
gas
Kr Ne
Xe Ar He
hXeXeXeXe
heatXeXe
XeXeeXe
XeXeXe
2*2
*
***
**2
2
hXeXeXe 2*
LAr128~
LXe175~
LNe5.77~
Effect of Ionization Density on Time Dependence
A.Hitachi PRB 27 (1983)5279
XENON R&D Goals: Summary
+ PMTs operation in LXe+ > 1 meter in LXe+ > 1 kV/cm electric field+ dual phase operation+ Reliable Cryogenic System+ Nuclear recoil Scintillation Efficiency (10-55 keVr) + Nuclear recoil Ionization Efficiency + Electron/Nuclear recoil discrimination+ Kr removal for XENON10+ Electric Field / Light Collection Simulations+ Background Simulations + Materials Screening for XENON10+ Assembly of XENON10 System+ Low Activity PMTs + Alternatives Readouts (SiPMs,LAAPDs,MCPs,GEMs..)
AchievedAchievedAchievedAchievedAchievedAchievedAchievedAchieved
Purification of 22 kg of Xe ongoing Tools Developed_Done for XENON10
Tools Developed_Done for XENON10All major components screened
AchievedVerified Hamamatsu #’s
Studies ongoing
Recent Highlights from XENON R&D
LXe Scintillation Efficiency for Nuclear Recoils The most important parameter for DM search No prior measurement at low energies
Aprile at al., Phys. Rev. D 72 (2005) 072006
LXe Ionization Efficiency for Nuclear Recoils XENON concept based on simultaneous detection of recoil ionization
and scintillation No prior information on the ionization yield as a function of energy and
applied E-field Aprile et al., PRL (2006), astro-ph/0601552
Development of XENON10 Experiment for Underground Deployment
Validated Cryogenics, HV, DAQ systems with 6kg prototype (XENON3) Demonstrated low energy threshold and 3D position reconstruction Installed/tested larger (15 kg) detector in same cryostat (Dec 05- Feb06) XENON10 equipment shipped to Italy on March 2, 2006
Xe-Recoils Scintillation Efficiency
p(t,3He)n
Borated Polyethylene
Lead
LXe
L ~ 20 cm
BC501AUse pulse shape discrimination and ToF to identify n-recoils
Columbia RARAF2.4 MeV neutrons
Aprile et al., Phys. Rev. D 72 (2005)
[Columbia and Yale]
Xe-Recoils Ionization Yield
• 1st Measurement of the charge of low energy recoils in LXe and of the field dependence.
• Charge yield surprisingly higher than expected and with very weak field dependence.
Energy threshold: 10 keVr
[Columbia, Brown and Case]
ELASTIC Neutron Recoils
INELASTIC 129Xe40 keV + NR
INELASTIC 131Xe80 keV + NR
137Cs source
Upper edge -saturation in S2
AmBe n-sourceNeutron
ELASTIC Recoil
5 keVee energy threshold = 10 keV nuclear recoil
Background discrimination capability
Neutron Inelastic 19F110 keV 40 keV
ELASTIC Nuclear Recoil
Teflon (PTFE)
Liquid Xenon
Gas Xenon
P. Majewski
L.Viveiros/R.Gaitskell
Rejection limited by edge gamma event contamination due to field irregularities
nuclearrecoil electron
recoil
improvement expected with XY position sensitive detector
XENON3: the first 3D sensitive dual phase XeTPC
10 cm
Hamamatsu R8520 PMT:Compact metal channal: 1 inch square x 3.5 cm
Quantum Efficiency: >20% @ 178 nm
10 cm
x and y found at minimum chisq
# of PMTs(top only)
S2 experimental value
(# of photoelectrons)
Expected S2 from simulation for all
possible x and y at every 1x1 mm2 pixel
Fluctuation of PMT signals (# of pe, gain,
analysis error)+
Uncertainties from simulation
(geometry, statistical)
a low energy event in the center, near LXe/GXe interface
S2
S1
~ 9 keVee
σ~1 cm
an edge event with long drift time
S2
S1
σ~2 mm
Edge events can be well identified
Pos III
Co-57(Pos I)
Co-57(Pos III)
Co-57(Pos II)
Pos II
Pos I
XENON3: Edge events effectively removed by radial cut
XENON3’s response to neutrons (2.5 MeV from D-D generator) at 1 kV/cm drift field
Neutron Elastic Recoil
40 keV Inelastic (129Xe)+ NR
80 keV Inelastic (131Xe)
110 keV inelastic (19F)+ NR
Neutron Elastic Recoil
40 keV Inelastic (129Xe)+ NR
80 keV Inelastic (131Xe)+ NR
XENON10: Expected Position Sensitivity from Simulation
Assumptions for GEANT4 Simulation
48 PMTs on top, 41 on bottom8 inch diameter, 6 inch drift length
about 15 kg liquid xenon
8 inches
Fitting from measurements by Columbia and XENON Collaborators (En
in keVr), see: Aprile et al., Phys. Rev. D 72 (2005) 072006 Aprile et al., astro-ph/0601552
Top PMT Array Bottom PMT Array, meshes, PTFE
10 keV nuclear recoils
XENON10: Expected Position Resolution
S2 signal for each PMT from simulation, convoluted by S2 resolution and
statistical fluctuation of photoelectrons in PMTs
Reconstructed positions obtained by the minimum chisq method (same as
for XENON3)
Position reconstruction for XENON10: a 122
keV gamma event from side (data)
r [mm]
Position resolution (σ) is less than 3 mm for 10 keV nuclear recoil events
XENON10: Identify Multiple-step Events
One neutron event with two steps(5 keVr each) separated by ΔL Events with two steps separated by
more than 3 cm in XY can be efficiently identified.
ΔL
Simulation for XENON10
nn
LXe
Events with ΔZ < 2 mm can be identified by the chisq value from XY position reconstruction.
Most of the multiple scattering events can be easily identified by drift time separation (ΔZ > 2 mm).
A two-step (ΔZ ~ 5 mm) event from XENON3
S1 S2
1st step
2nd step
• Tested all systems prior to shipping to LNGS
• 48 PMTs on top, 41 on bottom, 20 cm diameter, 15 cm drift length
• 22 kg of Xe to fill the TPC. Active volume ~15 kg.
XENON10 TPC at Columbia Nevis Laboratory
XENON10 at Gran Sasso National Laboratory
XENON10
• Shield Construction started in XENON Box ( ex-LUNA)• Testing/Calibrating unshielded XENON10 (March-April 06) in neighboring Box
LNGS: March 12, 2006