Transcript Studies of the Scintillation and Ionization Properties of

RWTH Aachen Graduate College – Bad Honnef
XENON10: Searching For
Dark Matter with a Noble
Liquid TPC
Aaron Manalaysay
Dept. of Physics, University of Florida
August 31, 2006
OVERVIEW
•Background
•Detection
•Using Liquid Xenon
•UFXenon
•XENON10
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BACKGROUND
Evidence and Motivation
Galactic rotation curves
Cosmic Microwave Background
 M h 2  0.13500..008
009
b h 2  0.0224  0.0009
Big Bang Nucleosynthesis
Gravitational Lensing
b h 2  0.02000..003
002
D. Clowe, et al , astro-ph / 0608407
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BACKGROUND
Content of the Cosmos
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BACKGROUND
Thermal Relics from Freezout
Leaving equilibrium as universe
expands:
In equilibrium:
X+X
Y+Y
27
3 -1
3

10
cm
s
2
X h 
 Av
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BACKGROUND
Some Properties of Dark Matter
•Distributed in spherical halo throughout galaxy
•Electrically neutral
•Non-relativistic (“cold”)
•Weak cross section
•Non-baryonic
Candidate: WIMP
(Weakly Interacting Massive Particle)
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DETECTION
WIMP Detection Scheme
cc annihilation
cq scattering
c
c+c
+q
c+q
q + q
0-50 keV nuclear recoils
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DETECTION
WIMP interactions: expected 5-50 keV nuclear recoils
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Using LXe
Why Xenon?
•Intrinsic Scintillator
•Large target nuclei (z=54, a~130-ish)
•Easily scaled up in mass
•Inert gas: safe and easy to work with
(and obtain)
•Easy Cryogenics at ~180K
•Suitable for spin-dependent and spinindependent WIMP interactions
•No long-lived radio isotopes
•Self-shielding
•Allows for nuclear recoil discrimination
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Using LXe
Interaction Process
Er
Ionization
Rel. Scintillation Yield
Xe++e+Xe
5.5 MeV alphas
56.5 keV n-recoils
Xe2+
+e-
Excitation
Xe*
Xe**+
Xe
+Xe
122 keV gammas
Ionization yield from alphas
Xe2*
178nm
Triplet (27ns)
2Xe
178nm
Singlet (3ns)
Nevis Lab data
Aprile et al.
2Xe
S. Kubota et al.
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Using LXe
Dual Phase TPC
PMT
PMT
GXe
Es
ee-
e-
e-
Ed
LXe
Cathode
Nuclear
recoils
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Inelastic
(40keV+NR)
Inelastic
(80keV+NR)
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UFXenon
UFXENON Detector Design
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UFXenon
Monte Carlo simulations
Simulated energy spectrum and position info.
Need to simulate light collection efficiency.
Ba133
g
Counts
Ba133
Energy [keV]
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UFXenon
Studying Nuclear Recoils
LXe
n
AmBe
q
Study nuclear recoils down to 5keV
recoils. Absolute recoil energy
inferred from recoil angle and ToF.
Er  En
2mn mXe
(1  cos q )
2
(mn  mXe )
gammas
EJ301
neutrons
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UFXenon
Scintillation and Ionization Yields
Ionization yield
These measurements are essential for
performing nuclear recoil discrimination.
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UFXenon
Additional Scintillation Efficiency Measurement
Scintillation efficiency
0.4
Preliminary data from Lopes et al
indicates possible departures from
the predictions of the Hitachi
model.
0.3
0.2
0.1
0.0
10
100
Recoil energy (keV)
Lopes et al
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XENON
XENON Collaboration
RWTH Aachen /
University of Florida
Brown University
Rick Gaitskell, Peter Sorensen, Luiz de Viveiros, Simon Fiorucci
Laura Baudis, Joerg Orboeck, Jesse Angle, Aaron Manalaysay
Case Western Reserve University
Tom Shutt, Alexander Bolozdyna, Paul Brusov, John Kwong,
Eric Dahl
Francesco Arneodo, Alfredo Ferella
Lawrence Livermore National Laboratory
Universidade de Coimbra
Adam Bernstein, Norm Madden, Celeste Winant, Chris Hagmann
Jose Matias, Joaquim Santos, Luis Coelho
Columbia University
Elena Aprile, Karl Giboni, Masaki Yamashita,
Guillaume Plante, Maria Monzani
Laboratori Nazionali del Gran Sasso
Yale University
Dan McKinsey, Richard Hasty, Angel
Manzur, Taritree Wongjirad, Kaixuan Ni
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Rice University
Uwe Oberlack, Roman Gomez, Peter Shagin
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XENON10
XENON10, 100, 1T
Gran Sasso
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Lead Shield
XENON10
XENON10
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XENON10
XENON10 Background MC Simulations
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XENON10
Current Status/Future Plans
•Energy threshold ~10 keV
•First data (post shield construction) was dominated by Kr
contamination (~25ppm)
•Replaced with Xe of low Kr (<1ppm) for calibration (the
current status)
•Neutron calibration starting in September
•Fill with ultra-low Kr level Xe (<1ppb) in September/October
Corno Grande, Gran Sasso
•Low-background data
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