First Dark Matter Results
From The LUX Experiment
Carmen Carmona
UCSB
February 28th, UCLA Dark Matter 2014
Sanford Underground Research
Facility (SURF) in Lead, SD
LUX experiment, Davis cavern
4850 feet deep
(~1.5 km)
LUX
Muon flux reduced by 107 (4.3 km.w.e)
Carmen Carmona - UCSB
Feb, 2013
2
Direct Detection Principle
WIMPs scatter
elastically off nuclei
• neutrons are
indistinguishable
background
• γ and e- scatter off
atomic electrons
Carmen Carmona - UCSB
3
Dual Phase Xenon TPC
•Excellent 3D imaging capability
Z position from S1 - S2 timing
X-Y positions from S2 light pattern
•S2 / S1 ratio => ER vs NR discrimination
log10(S2/S1)
Gamma Calibration (137Cs)
XENON10 Neutron Calibration (AmBe)
Recoil Energy (S1+S2) [keV]
Carmen Carmona - UCSB
4
The LUX Detector
✤
370 kg Xe TPC (active volume: 48 cm height, 47 cm diameter)
✤
Cooling system based in thermosyphons
✤
Heat exchanger system and high flow plumbing for rapid circulation through
external purifier (229kg/day)
✤
Water tank shielding (300 tons of water, ∅=8m, h=6m)
✤
122 ultra low background PMTs
NIM. A 704,
111-126 (2013)
arXiv:1211.3788
Radiation shield
2.75m
Ti Cryostats
Top PMT array
Thermosyphon
Anode grid
3.50m
1.20m
PMT holding
copper plates
Bottom PMT array
Carmen Carmona - UCSB
PTFE reflector
panels and field cage
Cathode grid
5
LUX Internals
HV Grids
Radiation shield
PTFE
reflector
panels
122 2” PMTs (Hamamatsu R8778)
• QE (175 nm) ~33%
• U/Th ~9/3 mBq/PMT
Dodecagonal
field cage
Copper PMT holding plate
2 x 61 PMT Array
Carmen Carmona - UCSB
PTFE “trifoils”
Counterweight
6
Backgrounds
Event Rate for E < 5 keVee in
118 kg fiducial volume
Background
Component
Source
10-3 x evts/keVee/
kg/day
Gamma-rays
Internal Components
including PMTs (80%),
Cryostat, Teflon
1.8 ± 0.2stat ± 0.3sys
127Xe
Cosmogenic
(36.4 day half-life) 0.87 → 0.28 during run
0.5 ± 0.02stat ± 0.1sys
214Pb
222Rn
0.11-0.22(90% CL)
85Kr
Reduced from
130 ppb to 3.5 ± 1 ppt
0.17 ± 0.10sys
Predicted
Total
2.6 ± 0.2stat ± 0.4sys
Observed
Total
3.6 ± 0.3stat
Measured DRU, 89 livedays
Log10 (DRUee)
r<18 cm
z=7-47 cm
Last 44 days
.. and dropping!
*See talk by S. Fiorucci at 12:15pm
Carmen Carmona - UCSB
7
Typical Event in LUX
S2 summed across all channels
S1 summed across all channels
0.6
8
amplitude (phe/10 ns)
amplitude (phe/10 ns)
0.5
0.4
0.3
0.2
0.1
6
4
2
0
0
−0.2
0
time (µs)
0.2
179
0.4
180
181
182
time (µs)
183
184
amplitude (phe/10ns)
triggered on S2
1.5
1
0.5
150
100
0
50
2 phe S1event
(near threshold)
Carmen Carmona - UCSB
0
50
100
150
200
0
PMT channel
number
time (µs)
8
Light Yield
• Light yield well measured down to 3 keVnr
• Modeled using Noble Element Simulation Technique (NEST).
• NEST based on canon of existing experimental data.
• Includes predicted electric field quenching of light signal, to 77-82% of the zero field light yield
Data 35 2:20:25 PM 10/28/13
9.2
9
Zero field
8.8
Artificial cut-off
at 3 keVnr
8.6
8.4
8.2
Carmen Carmona - UCSB
8
NEST:
Zero field
181 V/cm
*For details about NEST
see talk by M. Szydagis
at 12:45 pm
9
ER and NR Bands Calibration
Tritium(a)
injection
for
ER Calibration
Tritium ER
Calibration
−1
10
1
0.4
keVee
0.8
1.3
1.8
2.4
2.9
3.5
4.1
4.6
2.5
leakage
fraction
leakage fraction
1.5
(b) AmBe and Cf−252 NR Calibration
AmBe
and Cf-252 NR Calibration
b
log (S2 /S1) x,y,z corrected
2
99%
−3
10
99.9%
−4
0
5
10
15
20
S1 x,y,z corrected (phe)
25
30
99.99%
10
S1 (phe)
1.5
Black: leakage from counting events from the dataset
Red: projections of Gaussian fits below the nuclear
recoil band mean
3
keVnr
0
−2
10
10
2
1
90%
discrimination
discrimination
2.5
99.6% background rejection in
low energy region of interest
6
9
10
12
15
18
21
20
30
S1 x,y,z corrected (phe)
24
27
40
50
Gray contours indicate constant energies
using a S1-S2 combined energy scale
*See talk by J.Verbus at 12:30pm
Carmen Carmona - UCSB
Kr-83m
injection
10
LUX Absolute Nuclear Recoil Calibration Using a
Mono-Energetic D-D Neutron Source
Water
Tank
e- e- e
e- e e
θ e
D-D
neutron
generator
Monochromatic
2.5 MeV
neutrons
LXe
Blue Crosses - LUX DD
Black Dashed Line - NEST
Drift time (μs)
Current analysis 3keVnr cut-off
Current LUX 2014
PRL Conservative!
Blue Crosses - LUX DD
Black Dashed Line - NEST
y distance into LXe (cm)
Carmen Carmona - UCSB
*See talk by J.Verbus
at 12:30 pm
11
S1 Efficiency
•Universal S1 efficiency
— AmBe
NR calibration
— Tritiated-Methane calibration
— Full Monte Carlo of NR events (S1+S2 processed by same analysis chain)
— Mono-energetic d-d neutron source
relative differential rate
o LUX AmBe Neutron Calibration S1 data
1.8
– Monte Carlo S1 LUXSim/NEST
2
10
1.6
gray & red Efficiency from AmBe data
1.4
1.2
1
1
10
0.8
0.6
Efficiency from LUX Tritium data,
applied to ER background model for PLR
0.4
Flat energy source nuclear recoil sims,
applied to WIMP signal model for PLR
0
10
0
10
Carmen Carmona - UCSB
1
10
S1 x,y,z corrected (phe)
relative detection efficiency
2
0.2
2
0
10
12
WIMP Detection Efficiency
3 keVnr
S2area ~230 phe (8.9 extracted electrons)
S1area ~2.0 phe
Efficiency falls >18 keVnr due
to S1 req. [2,30] phe range
7.5 keVnr >95%
4.3 keVnr 50%
3 keVnr 17%
Including analysis cuts:
Efficiency for S1+S2 identification
( S1area>2 phe, S2area>200 phe )
Before any analysis cuts:
S1 pulse identification
S2 pulse identification
S1+S2 singles identification
True Recoil Energy equivalence based on LUX 2013 Neutron Calibration/NEST Model
Carmen Carmona - UCSB
13
LUX WIMP Search, 85.3 live-days, 118 kg
Accepted by PRL, arXiv:1310.8214
2.6
log10(S2b/S1) x,y,z corrected
2.4
160 events observed (1.9 evts/d)
Expect 0.64±0.16 leakage below NR mean
Distribution consistent with ER backgrounds
2.2
2
1.8
1.6
1.4
1.2
1
0
Carmen Carmona - UCSB
127Xe
10
20
30
S1 x,y,z corrected (phe)
5 keVee
40
50
14
Spin Independent Sensitivity
LUX is the most sensitive experiment in the world!
WIMP−nucleon cross section (cm2)
Edelweiss II
ZEPLIN III
CDMS II Ge
XENON100(2011)-100 live days
−44
10
XENON100(2012)-225 live days
LUX (2013)-85 live days
−45
10
LUX +/-1σ expected sensitivity
1
10
Carmen Carmona - UCSB
2
10
mWIMP (GeV/c2)
3
10
15
Low Mass WIMP Sensitivity
CDMS II Ge
DAMA/LIBRA Favored
CoGeNT Favored
CRESST Favored
CDMS II Si Favored
XENON100(2012)-225 live days
>20x more sensitivity
LUX (2013)-85 live days
Carmen Carmona - UCSB
LUX +/-1σ expected sensitivity
16
Projected LUX 300 day WIMP Search Run
•Post-Run3 items
first results from calibration
with mono-energetic d-d neutrons
in LUX. More to come from the analysis
✦Looking at improving E-field
✦Important
•New run of 300 live-days in 2014/15
✦Extending
sensitivity by factor >5
✦WIMP discovery still possible
•Beyond LUX: LZ
✦~50x
increase in fiducial volume (see talk
by H. Nelson at 2:15pm)
•Stay tuned for more results...
Carmen Carmona - UCSB
LUX (2013)
85 LIVE DAYS
LUX (2014/15)
300 LIVE DAYS
17
LUX Collaboration: ~100 scientist from 17 institutions
Brown
Richard Gaitskell
Simon Fiorucci
Monica Pangilinan
Jeremy Chapman
David Malling
James Verbus
Samuel Chung Chan
Dongqing Huang
PI, Professor
Research Associate
Postdoc
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Case Western
Thomas Shutt
Dan Akerib
Karen Gibson
Tomasz Biesiadzinski
Wing H To
Adam Bradley
Patrick Phelps
Chang Lee
Kati Pech
PI, Professor
PI, Professor
Postdoc
Postdoc
Postdoc
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Imperial College London
Henrique Araujo
Tim Sumner
Alastair Currie
Adam Bailey
PI, Reader
Professor
Postdoc
Graduate Student
Lawrence Berkeley + UC Berkeley
Bob Jacobsen
Murdock Gilchriese
Kevin Lesko
Carlos Hernandez Faham
Victor Gehman
Mia Ihm
PI, Professor
Senior Scientist
Senior Scientist
Postdoc
Scientist
Graduate Student
Lawrence Livermore
Adam Bernstein
Dennis Carr
Kareem Kazkaz
Peter Sorensen
John Bower
PI, Leader of Adv. Detectors Group
Mechanical Technician
Staff Physicist
Staff Physicist
Engineer
LIP Coimbra
Isabel Lopes
Jose Pinto da Cunha
Vladimir Solovov
Luiz de Viveiros
Alexander Lindote
Francisco Neves
Claudio Silva
PI, Professor
Assistant Professor
Senior Researcher
Postdoc
Postdoc
Postdoc
Postdoc
Carmen Carmona - UCSB
Collaboration Meeting, UC Davis, October 2013
SD School of Mines
Xinhua Bai
Tyler Liebsch
Doug Tiedt
PI, Professor
Graduate Student
Graduate Student
SDSTA
David Taylor
Mark Hanhardt
Project Engineer
Support Scientist
Texas A&M
James White †
Robert Webb
Rachel Mannino
Clement Sofka
PI, Professor
PI, Professor
Graduate Student
Graduate Student
UC Davis
Mani Tripathi
Bob Svoboda
Richard Lander
Britt Holbrook
John Thomson
Ray Gerhard
Aaron Manalaysay
Matthew Szydagis
Richard Ott
Jeremy Mock
James Morad
Nick Walsh
Michael Woods
Sergey Uvarov
Brian Lenardo
PI, Professor
Professor
Professor
Senior Engineer
Senior Machinist
Electronics Engineer
Postdoc
Postdoc
Postdoc
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Graduate Student
UC Santa Barbara
Harry Nelson
Mike Witherell
Dean White
Susanne Kyre
Carmen Carmona
Curt Nehrkorn
Scott Haselschwardt
PI, Professor
Professor
Engineer
Engineer
Postdoc
Graduate Student
Graduate Student
University College London
Chamkaur Ghag
Lea Reichhart
PI, Lecturer
Postdoc
University of Edinburgh
Alex Murphy
Paolo Beltrame
James Dobson
PI, Reader
Research Fellow
Postdoc
University of Maryland
Carter Hall
Attila Dobi
Richard Knoche
Jon Balajthy
PI, Professor
Graduate Student
Graduate Student
Graduate Student
University of Rochester
Frank Wolfs
Wojtek Skutski
Eryk Druszkiewicz
Mongkol Moongweluwan
PI, Professor
Senior Scientist
Graduate Student
Graduate Student
University of South Dakota
Dongming Mei
Chao Zhang
Angela Chiller
Chris Chiller
Dana Byram
PI, Professor
Postdoc
Graduate Student
Graduate Student
*Now at SDSTA
Yale
Daniel McKinsey
Peter Parker
Sidney Cahn
Ethan Bernard
Markus Horn
Blair Edwards
Scott Hertel
Kevin O’Sullivan
Nicole Larsen
Evan Pease
Brian Tennyson
Ariana Hackenburg
Elizabeth Boulton
PI, Professor
Professor
Lecturer/Research Scientist
Postdoc
Postdoc
Postdoc
Postdoc
Postdoc
Graduate Student
Graduate Student
Graduate Student
Graduate Student
Graduate Student
18