Direct Dark Matter Detection with XENON

The XENON100 Dark Matter Experiment

Blank

Elena Aprile Columbia University

The Dark Side of the Universe, Cairo, June 2, 2008 Direct Dark Matter Detection

χ Elastic Scattering χ Galactic Direct Detection Methods/Experiments WIMP Halo (ρ = 0.3 GeV/cm3) Target Recoil Nucleus Nucleus ~10-100 keV or less = 220 km/s

-47 2 σχ-p can be as low as 10 cm

2 Direct Detection Rates

WIMP Scattering Rates requirements for direct DM detectors

18 evts/100-kg/year ➡ large mass (scalability) (Eth=5 keVr) 8 evts/100-kg/year ➡ (Eth=15 keVr) low energy threshold

➡ background suppression

➡ deep underground / passive shield

➡ low intrinsic radioactivity

➡ gamma background discrimination

3 Direct Detection Methods/Experiments

XENON, XMASS-II, ZEPLIN2, ZEPLIN3, WARP, ArDM Double Phase (Xe, Ar) DAMA/LIBRA ZEPLIN1 XMASS Mini-CLEAN

EDELWEISS CDMS CRESST

4 TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University World Wide Dark Matter Searches

Boulby SNOLAB ZEPLIN DEAP/CLEAN DRIFT PICASSO Yangyang SUSEL KIMS LUX

Frejus/ Modane EDELWEISS Kamioka Soudan Canfranc XMASS CDMS ANAIS ArDM Gran Sasso CRESST DAMA/LIBRA WARP XENON

5 Cryogenic Noble Liquids: Basic properties

• Suitable materials for detection of ionizing tracks:  Dense, homogeneous, target and also detector  Do not attach electrons  High electron mobility (except neon in some conditions)  Commercially easy to obtain and to purify  Inert, not flammable, very good dielectrics

Liquid Radiation Collision Electron Energy loss Boiling point Density length length mobility Cost Element @ 1 bar (K) ( /cm3) dE/dx (MeV/cm) (cm2/Vs) ρ X0 (cm) λ (cm)

Neon 1.2 1.4 24 80 27.1 high&low $

Argon 1.4 2.1 14 80 87.3 500 $$

Krypton 2.4 3.0 4.9 29 120 1200 Xenon 3.0 3.8 2.8 34 165 2200 $$$ The Merits of Liquid Xenon for Dark Matter Detection

Recombination depends on type of recoils (stronger for nuclear recoils) Xe+ Ionisation +Xe ✦scalability : relatively cheap ($1500/ Electron/nuclear recoil kg) and “easy” cryogenics at 170 K + Xe2 Excitation ✦bkg reduction: via self-shielding +e- (recombination) intrinsic background free: Kr in Xe wavelength ✦ depends on gas Xe* Xe** + Xe can be puriﬁed to ppt level e.g. Xe 175nm Ar 128nm +Xe ✦low threshold : high scintillation yield Xe * ✦gamma rejection: electron and nuclear 175nm 2 175nm Triplet Singlet recoil discrimination 27ns 3ns

time constants 2Xe 2Xe depend on gas e.g. Xe 3/27ns Nigel Smith, RAL Ar 10/1500ns

7 Two-phase Xenon Detectors for Dark Matter Detection

Top PMT Array WIMPs/Neutrons

nuclear recoil

Gammas

electron recoil

8 world-wide two-phase xenon dark matter detectors previous generation current generation next generation 10~30 kg 170~300 kg ton scale (2006 - 2007) (2007-2009) (2009-2012)

XENON10 XENON100 XENON1T

Text

ZEPLIN-II ZEPLIN-III LUX XMASS two phase （2008 - ?)

9 world-wide two-phase xenon dark matter detectors previous generation current generation next generation 10~30 kg 170~300 kg ton scale (2006 - 2007) (2007-2009) (2009-2012)

XENON10 XENON100 XENON1T

Text

ZEPLIN-II ZEPLIN-III LUX XMASS two phase （2008 - ?)

9 The XENON10 Detector

✦ Pulse Tube refrigerator: stable operation at 170 K Pulse tube ✦ TPC active volume: 20 cm (Φ) x 15 cm (H) - 15 kg refrigerator ✦ PTFE Teﬂon: ~95% UV reﬂectivity at 175 nm ✦ 89 PMTs (R8520): 20% QE, low radioactivity

89 PMTs PTFE 15 kg LXe

10 The XENON10 Detector

89 PMTs PTFE 15 kg LXe

10 XENON10 at Gran Sasso Underground Laboratory (Italy)

XENON10 Pb/Poly Shield Detector

3100 mwe ﬂat overburden (surface muon ﬂux reduced by 106)

11 Self-shielding in XENON10 Detector

near top PMTs near bottom PMTs

Fiducial Volume

Z (15 cm total)

15 < drift time < 65 μs, r < 80 mm (5.4 kg ﬁducial mass) Overall Background in Fiducial Volume ~0.6 event/(kg day keVee)

12 XENON10 Gamma/Neutron calibration

~ 99.5 % gamma events are rejected below the nuclear recoil mean WIMP-Nucleon Cross-Section Upper Limits (90% CL)

Phys. Rev. Lett. 100, 021303 (2008)

current results treating the 10 events as WIMP candidates CDMS II (NO BKG SUBTRACTION) 8.8 x 10-44 cm2 at 100 GeV -44 2 XENON10 4.5 x 10 cm at 30 GeV

supersymmetry models

14 XENON10 SD WIMP-Nucleon Cross Section Upper Limits (90 % CL)

Angle et al. :arXiv 0805.2939, submitted to Phys. Rev. Lett. Natural Xe has non-zero nuclear spin isotopes: 129Xe (spin-1/2) @ 26.4% and 131Xe (spin-3/2)@ 21.2%. Both contain unpaired neutrons thus XENON10 is mostly sensitive to WIMP-neutron spin-dependent couplings, yielding the best sensitivity to-date.

pure neutron couplings pure proton couplings

ZEPLIN-II KIMS: CsI CDMS-II 73Ge XENON10 ZEPLIN-II NAIAD CDMS-II 73Ge KIMS: CsI XENON10 PICASSO

CMSSM

SuperK

CMSSM

15 XENON10 Heavy Majorana NeutrinoUpper Limits (90 % CL)

16 Feb 08: CDMS Reports a new WIMP-Nucleon Cross Section Limit

17 XENON100 : the current step in the XENON program (2007-09)

A new and improved TPC design guided by the XENON10 experience and for the same underground location and passive shielding

Bell • 170 kg LXe (vs. 20 kg in XE10); 50 kg ﬁducial mass (vs. 5 kg in XE10). Grids x10 ﬁducial mass Structure Top PMTs • 242 R8520 PMTs with lower Teflon background and higher QE (vs. 89 in Panels with Active LXe Target HV XE10) Racetracks • lower background stainless steel Active LXe Shield cryostat and inner chamber Bottom PMTs • a factor of 100 lower background Shield PMTs Cathode Mesh

Vacuum Cryostat

18 The XENON100 TPC Assembly: the

170 kg LXe (70 kg target)

19 20 Xe Puriﬁcation System Status of XENON100: Installed Underground at LNGS

• Shield modiﬁcation/improvement:Jan 08 • Detector underground: Feb 08 • Xe Puriﬁcation/ Kr-distillation: May-June 08 • Gamma/Neutron Calibration: May-July 08 • 1st DM Search: Aug-Sep 08 XENON100 (Feb.2008) XENON10 (2006-2007)

2243 XENON100 Inside Shield

XENON100 Outside Shield XENON100: Materials Radioactivity Measurements

PMTs

238U 232Th 60Co 40K Sample Detector (mBq/PMT) (mBq/PMT) (mBq/PMT) (mBq/PMT)

23 HQE PMEs GeMPI2 0.16 ± 0.05 0.46 ± 0.16 0.73 ± 0.07 14 ± 2

39 PMTs GeMPI2 0.12 ± 0.01 0.11 ± 0.01 1.5 ± 0.1 6.9 ± 0.7

48 PMTs GeMPI2 0.11 ± 0.01 0.12 ± 0.01 0.56 +/- 0.04 7.7 +/- 0.8

22 HQE PMTs Gator < 0.64 0.18 ± 0.06 0.60 ± 0.1 12 ± 2

24 XENON100: Expected gamma background rate

Operating the detector for two months (~3000 kg-d exposure) will give: <1 background event (with 99.5% ER rejection, within 10 keVee window) 25 XENON100: Expected gamma background rate

0.01 evt/kg/keVee/day (10 mdru) in 50-kg ﬁducial mass

Operating the detector for two months (~3000 kg-d exposure) will give: <1 background event (with 99.5% ER rejection, within 10 keVee window) 25 XENON100 Sensitivity Reach by 2008

CDMS II

XENON10

26 XENON100 Sensitivity Reach by 2008

CDMS II

XENON10

XENON100

26 The XENON100 Collaboration

DOE + NSF NSF NSF Switzerland Portugal Italy

Katsushi Arisaka Hanguo Wang h UCLA XENON1T: The Next Step in XENON Program

Liquid Xe (2.4 ton)

Radiation- free Photon Detector (3” QUPID, Total 968)

1 m PTFE Spacer

OFHC or Ti Vacuum Vessel

06/01/08 13 Comparison of Low-radioactive PMTs R8520 R8778 QUPID 1 inch 2 inch 3 inch

XENON10 XMASS XENON1T

06/01/08XENON100 KatsushiLUX Arisaka, UCLA Super-XENON 28 From XENON10 to XENON1T

XENON10 XENON100 XENON1T Detectors (2006-2007) (2007-2009) (2009-2012)

Fiducial Mass (kg) 5 50 1000 Gamma background (dru: 1 10-2 goal: <10-4 events/kg/keV/day) Neutron < 1 per year < 1 per year goal: < 1/two years background

Exposure 2 months 2 months 2 year

lower bkg, higher QE Photodetectors R8520 QUPID (or + R8520) R8520 WIMP 2 x 10-45 cm2 3 x 10-47 cm2 Sensitivity 0.9 x 10-43 cm2 (projected) (projected) at 100 GeV