direct dark matter detection S Moriyama Institute for Cosmic Ray Research University of Tokyo Oct 8 th 2011 FPUA2011 Okayama Japan Principle of direct detection in Lab ID: 449410
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Slide1
Recent progress of direct dark matter detection
S. Moriyama
Institute for Cosmic Ray Research, University of Tokyo
Oct. 8
th
, 2011 @ FPUA2011, Okayama, JapanSlide2
Principle of direct detection in Lab.Dark matter hit detectors in Lab. Why interaction expected?
Assume DM particles were thermally generated.
They annihilated into ordinary matter. This implies an interaction between dark matter and ordinary matter (atoms).
Weakly Interacting Massive Particles (WIMPs)
Dark matter
Dark matter
Ordinary matter
Ordinary matter
Annihilation
Scattering
1/temperature ~ time
Comoving
number densitySlide3
How much dark matter around us?
It can be estimated by measuring rotational curve of the galaxy. Local density ~ 0.3GeV/cc ~average x 10
5
Isothermal, Maxwell distribution
(<v> ~230km/s, <
b>~10-3).
R.P.Olling and M.R.Merrifield MNRAS 311, 369- (2000)
Buldge
Steller disk
Dark Halo
These dark matter particles are expected to cause nuclear recoils even in underground lab.Slide4
Signals after nuclear recoils
Small energy depositions (m
p
<v>2/2 < 1keV), rare.Scintillation light (photons), ionizations, phonons, etc are expected to be observed.
By combining multi. info., BG reduction is possible.
Scintillation
lights
+
+
+
-
-
-
Ionization
signals
Phonon
s
ignals
.
.....
Bubble
generationSlide5
Expected energy spectrum of nuclear recoil, ~O(10keV)
Coherent interaction with each nucleon in nuclei causes enhancement.
Target nuclei with similar mass to DM is the best choice.
Si
Ge
Xe
Si
Xe
Ge
Red: differential
,
Blue: integrated
R.J.Gaitskell, Ann. Rev. Part. Sci., 54 (2004) 315.Slide6
Another aspect: annual modulation
Due to a peculiar motion of the solar system inside the galaxy, relative velocity to the rest frame of dark matter varies over a sidereal year.
This causes the modulation of event rates and energy spectrum.Slide7
Unknown: mass and cross section!
Small mass: low energy threshold detector with light nucleus ~O(
GeV
/c2)Small cross section: massive and low BG detector ~O(1/day/ton)
3 orders/15years!
Mass of dark
matter particle
UNKNOWN
cross section
to nucleon UNKNOWN
True parameter
Detector with larger mass, longer
exposure and lower background
Detector with smaller atomic
number and low energy thresholdSlide8
Experiments all over the world >30!
XMASS
NEWAGE
PICO-LON
NIT
KIMS
PICASSO
CDMSCoGeNTCOUPPDEAP/CLEAN
SIMPLEDMTPCLUX
DAMA/LIBRAXENONCRESSTII
EDELWEISSZEPLINDRIFTWARPArDM
ANAISMIMACROSEBUD
PANDAXCDEX
DM-Ice
Not complete
TEXONO
Strong tension exists among experiments.
DAMA, CoGeNT, CRESSTII
XENON, CDMSSlide9
1. DAMA/NaI (7yr)
,
DAMA/LIBRA
(6yr), 430td
Antonella
, TAUP2011Slide10
Positive signal of annual modulation
Radioactive pure
NaI
(Tl): scintillation only, no PID.Strong signature of the annual modulation, ~9s
A lot of criticisms at the beginning, but later serious study/consideration started (light DM, IDM, etc.).
Influences of seasonal modulating cosmic muons
? An unnatural background shape is in doubt.
by Sep. 2009
Modulation of +/-2%Slide11
2. CoGeNT (Ge
) 140kgd
P-type point contact detector has very low noise thus low energy threshold due to small cap.
smaller-mass DM w/ ionization only
Science 332 (2011) 1144
PRL 101, 251301 (2008)
arXiV1106.0650
0Slide12
Assume all the unknown events from DM
Mod. (
c
2/dof=7.8/12) 80%C.L. accept.
Flat (c2
/dof=20.3/15) 84% C.L. reject. modulation is favored with 99.4%
C.L.
Is the contamination of surface
b
ackground well controlled??Slide13
3. XENON100, 4.8td
Particle ID possible
BG red.
Rafael,
TAUP2011Slide14
Observed data and calibration3 events remained
1.8+/-0.6BG expected (28%)
Observed data
Neutron source
(causes nuclear recoil)
calibration data
99.75% rejection line and
3 sigma contour of NR
DM
search window
(8.4-44.6keVnr)
Nuclear recoil
e/gammaSlide15
Status of dark matter search
DAMA, Na, 3
s
DAMA, I, 3
s
CoGeNT
(
Ge)90%5-7GeV
O.
Buchmueller et al.CMSSM (68%, 95%)arXiv:1106.2529Including 2010 LHC
XENON100 (Xe
)CRESST 2
s
3 orders of sensitivity improved over last 15 years!CDMS (
Ge)+CDMS(LE), XENON10(LE)Slide16
Recent “signals” of DM, axion, and n
2000: DAMA experiment (Gran
Sasso
) started to claim the observation of dark matter.
2005: PVLAS collaboration (INFN) axions?
2010/2011: CoGeNT (Soudan, US)
2011: CRESST II (Gran Sasso) 2011: OPERA (Gran
Sasso, CERN) observation of super-luminal neutrinosSlide17
Recent “signals” of DM, axion, and n
2000: DAMA experiment (Gran
Sasso
) started to claim the observation of dark matter.
>8s
now2005: PVLAS collaboration (INFN) axions
? withdrawn
2010/2011: CoGeNT
(Soudan, US)2011: CRESST II (Gran Sasso)
2011: OPERA (Gran Sasso, CERN) observation of super-luminal neutrinos
“Italian signals”
Further experimental check necessarySlide18
XMASS experimentSlide19
The XMASS collaborations
Kamioka Observatory, ICRR, Univ. of Tokyo
:
Y. Suzuki, M. Nakahata, S. Moriyama, M. Yamashita, Y. Kishimoto,
Y. Koshio, A. Takeda, K. Abe, H. Sekiya, H. Ogawa, K. Kobayashi,K. Hiraide, A. Shinozaki, S. Hirano, D. Umemoto, O. Takachio, K. Hieda
IPMU, University of Tokyo: K. Martens, J.Liu
Kobe University: Y. Takeuchi, K. Otsuka, K. Hosokawa, A. Murata
Tokai University: K. Nishijima, D. Motoki, F. Kusaba
Gifu University: S. Tasaka
Yokohama National University: S. Nakamura, I. Murayama, K. Fujii
Miyagi University of Education: Y. FukudaSTEL, Nagoya University
: Y. Itow, K. Masuda, H. Uchida, Y. Nishitani, H. TakiyaSejong University
: Y.D. KimKRISS:
Y.H. Kim, M.K. Lee, K. B. Lee, J.S. Lee
41 collaborators,10 institutesSlide20
Kamioka Observatory
1000m under a mountain = 2700m water equiv.
360m above the sea
Low cosmic ray flux (10-5)
Horizontal accessSuper-K for n
physics and other experiments in deep underground
KamLAND (Tohoku U.)
By courtesy of Dr. MiyokiSlide21
XMASS experiment
●
X
MASS
◎
Xenon MASS
ive detector for Solar neutrino (pp/
7Be)
◎ Xenon neutrino
MASS detector (double beta decay)
◎ Xenon detector for Weakly Interacting
MASSive Particles (DM search)
It was proposed that Liquid xenon was a good candidate to satisfy s
calability and low background.
As the first phase, an 800kg detector for
a dark matter search
was constructed.
Y. Suzuki, hep-ph/0008296
10ton FV (24ton) 2.5m
Solar
n
, 0
nbb
, DM
in future
100kg FV (800kg)
0.8m,
DM
First phaseSlide22
Structure of the 800kg detector
Single phase liquid Xenon (-100
o
C, ~0.065MPa) scintillator835kg of liquid xenon, 100kg in the
fiducial volume642 PMTs
5keVelectron equiv. (~25keVnuclear recoil
) thre.Slide23
BG reduction by self shielding effect
Photo electric effect starts to dominate @500keV: strong self shielding effect is expected for low energy radiations.
E (
keV
)
Attenuation length (cm)
water
~O(500keV)
Photo
Electric
Effect
Compton
effect
10cm
1cm
LXeSlide24
Event reconstructionSlide25
Demonstration of the detector performance
Calibration system
Introduction of radioactive sources into the detector.
<1mm accuracy along the Z axis.Thin wire source for some low energy
g rays to avoid shadowing effect.57
Co, 241Am, 109
Cd, 55Fe, 137
Cs..
Stepping
Motor
Linear
Motion
Feed-
through
Top
photo
tube
~5m
Gate
valve
4mm
f
0.15mm
f
for
57
Co source
Source rod with a dummy
sourceSlide26
High light yield and good position resolution
57
Co source at the center shows a typical response of the detector. High
p.e. yield 16.0+/-1.0p.e./keV
was obtained. Factor 3 higher than expected.The photo electron yield distribution was reproduced by a simulation well.Good position res. ~1cm obtained.
DATA
MC
[
keV
]
Reconstructed energy
122keV
136keV
59.3keV (W-Ka)
~4% rms
Data at various positions
+15VSlide27
Expected background
Major background
m
ust come from
radioactivity in PMTs though we developed low BG PMTs.
Radioactive impurityinside liquid xenona
lso must be low: 85Kr
distillation
Rn charcoal
BG ~ 10-4
/kg/keV/day is expected to be realized. (XENON100 ~0.5x10
-4/kg/keV/day)
Background in unit mass
Very low BG at low energySlide28
Expected sensitivity
XENON100
CDMSII
XMASS
2keVee
thre
. 100d
Black:signal+BG
Red:BG
Expected energy
spec.
1 year exposure
s
c
p
=10
-44
cm
2
50GeV WIMP
Spin Independent
XMASS
5keVee
thre
. 100d
Initial target of the energy
t
hreshold was ~5keVee.
Because we have factor ~3
better photoelectron yield,
lower threshold = smaller mass
dark matter may be looked for.Slide29
Assembly of PMT holder and installation of PMTsSlide30
Joining two halvesSlide31
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P-01
As of Sep. 2010Slide32
Summary
“Positive” signals by DAMA,
CoGeNT
, and CRESST-II (~10GeV, 10-40cm2
) are around the detector threshold where our knowledge on the detector systematic and background are not established. Further experimental confirmations are necessary, and on going.The XMASS 800kg detector aims to detect dark matter with the sensitivity 2x10
-45cm2 (spin independent case)
with LXe.
Commissioning runs are on going to confirm the detector performance and low background properties.Energy resolution and vertex resolution were as expected. ~1cm position resolution and ~4% energy resolution for 122keV
g.