Dark Matter Searches New Opportunities at CERN May 11-13, 2009

European Rare Event Calorimeter Array (EURECA) The Argon Dark Matter Search (ArDM) The XENON Dark Matter Detection Experiment Dark Matter Search with Bubble Chambers The GERDA Neutrinoless Double Beta Decay Experiment

Laura Baudis University of Zurich for above collaborations

Tuesday, May 12, 2009 Goal of Direct Detection Experiments

• Detect new, yet undiscovered particles, which may be responsible for the dark matter in our galaxy. Example: WIMPs = heavy (few GeV - few TeV), color and electrically neutral; in thermal equilibrium with the rest of the particles in the early universe, freeze out when MW>>TF

M ≈ 9 × 1010 M tot,lum  12 Mvirial ≈ 1...2 × 10 M Sun

ρ  0.3 GeVcm−3 χ ρ  3000 WIMPs ⋅ m−3 χ (MWIMP = 100 GeV)

(J. Diemand et all, Nature 454, 2008, 735-738) (Klypin, Zhao & Somerville 2002) Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Strategy for WIMP Direct Detection

MWIMP = 100 GeV • Elastic collisions with atomic nuclei -43 2 σWN=4×10 cm • Rates depend on: [mχ, σ], [f(v), ρ0], [N, Eth] ...

 v dR σ 0ρ0 2 max f (v,t) 3 = 2 F (ER ) 2 d v dE 2m µ ∫v> mN ER /2µ v R χ

Differential rates for Diff.keV)] d [events/(kg rate • With WIMP-nucleon cross sections different targets (SHM) -7 < 10 pb, the expected rates are Recoil energy [keVr]

< 1 event/100kg/day

• Energy of recoiling nuclei EURECA EURECA

 2 q µ2 2 E = = v (1− cosθ) ≤ 50 keV Bubble chamber R 2m m N N ArDM, XENON Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Status of Direct Detection DAMA: NaI Field (May 2009) KIMS: CsI

CDMS-II 73Ge Spin-dependent cross sections cross Spin-dependent Spin-independent cross section (normalized to nucleons)

] 129

2 XENON10: Xe DAMA/

[cm LIBRA SI SI EDELWEISS: 2005 CMSSM WARP: 2007

CRESST: 2008 σ WIMP-nucleon WIMP-nucleon DAMA: NaI

ZEPLIN III: 2008 XENON10: 129Xe CDMS: 2008 COUPP XENON10: 2008 KIMS: CsI CMSSM2008 (Roszkowski, Ruiz, Trotta) SuperK

WIMP Mass [GeV] CMSSM XENON10: PRL100, PRL101; ZEPLIN-III: arXiv:0901.3448, WARP: Astrop.Phys. 28 CDMS-II: PRL 102, DAMA/LIBRA: EPJ C 56, CRESST: Astrop.Phys. 31, EDELW: PRD71 Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Abstract by Hans Kraus, Oxford EURECA European Rare Event Calorimeter Array

A European coordinated effort to build a ton-scale cryogenic dark matter experiment

Joint effort of ~110 physicists from EDELWEISS, CRESST, ROSEBUD, CERN + others

Part of ILIAS / ASPERA / ApPEC strategy (roadmap)

Cryogenic detectors are modular and inherently scalable

Multi-element target for WIMP identiﬁcation (Ge and solid state scintillators)

Current topics:

design study, technology down selection

major effort in background control and detector fabrication

Preferred site: 60 000 m3 extension of present Laboratoire Souterrain de Modane

Tuesday, May 12, 2009 CRESST Detectors

reflecting cavity

Silicon tungsten TES absorber

CaWO4 absorber 300g

tungsten TES

Phonon – Scintillation

Energy scale: Particle Identification: Excellent resolution Background discrimination

Range of Scintillator Targets 18 Detector Modules installed 10keV threshold

Tuesday, May 12, 2009 Edelweiss (InterDigitised) Detectors

Phonon – Ionization

From plain to concentric alternate V Energy scale: Particle Identification: electrodes Excellent resolution Background discrimination

12 new detectors (400 g Ge) running with InterDigitized electrodes:

Removes “surface events” by avoiding incomplete charge collection  clean nuclear recoil band  one surface event expected in 3x104 kg days  equivalent to 10-45 cm2 sensitivity + decrease of surface (210Pb) background

Meets EURECA goal (see recent preprint: arXiv:0905.0753v1)

Tuesday, May 12, 2009 EURECA Aims EURECA = “European Rare Event Calorimeter Array”

DAMA/ LIBRA CRESST / EDELWEISS EDELWEISS: 2005 ~5×10−7 pb (spring 2009) WARP: 2007 CRESST: 2008 ~1 evt/kg/day ZEPLIN III: 2008 CDMS: 2008

XENON10: 2008 ~3 evt/kg/yr

EURECA aim

~30 evt/ton/year

Tuesday, May 12, 2009 EURECA in LSM Existing laboratory

Timeline:

2009/10: Design Study → TDR; currently preparing bid for ASPERA design study call

2011/12: Digging out of LSM extension begins. In parallel, begin construction of New LSM EURECA components away from LSM extension

Aim for ~100 kg stage (10−45 cm2).

2014: LSM extension ready to receive EURECA.

2015: Begin data taking and in parallel improve and upgrade.

2018: One tonne target installed.

Possible EURECA Facility Layout

Tuesday, May 12, 2009 EURECA CERN Involvement

Expertise of Technology and Engineering Departments: Design studies for large-scale shielding Planning, manufacturing of cryogenic infrastructure R&D of radio-pure cryogenic scintillator

Support Facilities: Use of CERN ﬁnance ofﬁce / administration of funds Meeting facilities Common procurement

Physics Studies: Coherent approach with LHC and direct DM searches Closer collaboration with Theory Division on interpretation of experimental data in the context of SUSY models and LHC results

Tuesday, May 12, 2009 A The ArDM-1ton experiment at CERN DM ETHZ - UniZ - Granada - CIEMAT - Warzsawa - Shefﬁeld Abstract by Andre Rubbia, ETHZ • Dual-phase LAr LEM-TPC to search for nuclear recoils induced by WIMPs • ≈850 kg target, viewed by 14 8” PMT + ﬁnely segmented LEM charge readout -44 2 • Goal: 30 keVr threshold, ≈ 1 WIMP event/ton/day at σSI≈10 cm • Status: surface operation at CERN to characterize detector • Underground deployment foreseen after successful tests on surface (2010?) Ionization readout Purification circuit

LAr Cooling circuit

Vacuum insulation

A.Rubbia, “ArDM: a Ton-scale liquid Argon experiment for direct detectionof dark matter in the universe”, J. Light readout Phys. Conf. Ser. 39 (2006) 129 11 Tuesday, May 12, 2009 Successfully Double phase LAr LEM-TPC demonstrated on small A novel kind of double phase LAr TPC based on a scale prototypes Large Electron Multiplier (LEM) Cosmic tracks in 3 lt prototype: Anode (arXiv:0811.3384) 6 mm pitch (with strips)

LEM concept based The top on pionieering Electrode successes of GEM of the LEM2 technology (with strips) X-t Y-t

LEM2 LEM1 Y-t LAr level

Charge X-t Cathode extraction grids

ETHZ preamp Digital F/E 256 channels σ≈10% (G≈10) PMT signal CAEN

Tuesday, May 12, 2009 A ArDM-1ton assembly & operation at CERN DM

Detector Field shapers HV UV shift/reﬂector

CuO cartridge (inside)

arXiv0904.0246 !"#$%&'($)*+)+$ 3/(453(

670%5"( LAr LAr blocked PMTsblocked Vacuum

Atmosphere

Figure 39: The flux through the cartridge is a linear function of the pressure difference. The elevation of the slope is the impedance.In collaborationFigure 28: The with liquid BIERI argon circuit is not in contact with the atmosphere. It is engineeringthermally insulated. Winterthur,Left: Piston Switzerland moves down, argon flows into the chamber. Right: Piston moves up, argon is pressed out towards the cartridge.

Forced LAr with bellow pump 8%59(4:40"(;$<(( Flux ≈ 20 lt LAr/hr temperature would be exactly the same as the one of the argon circuit. 5.2.2 Pneumatic drive and control of the pump Hamamatsu R5912 To move the piston, a pneumatic drive is installed. It is operated at a pressure of about 3 bar. It is regulated by a pressure regulator, connected to the air compression system of the experiment (See ﬁg. 29).Several valves are between the regulator and the inlet of 13 the pump. this reduces the pressure at the pump to about 2.2 1 bar. The compressed Tuesday, May 12, 2009 ±

8=>?:%@76#(;ABCDE<( !"#$%&"'()*&(+%,(-(./(012&( Figure 40: The impedance doesn’t depend on the absolute pressure bevore the cartridge.

has to be adjusted to get the maximum possible rate. ItFigure depends29: onThe the operating level and pressure no of the membrane pump is regulated down to absolute values can be given. around 2 bar.

air drives the piston up and down. Both parts of the cycle are operated by overpressure. The actual behavior of the piston, how fast it should move is controlled by a bleed valve.

53 42 A ArDM-1ton assembly & operation at CERN DM

Detector Field shapers HV UV shift/reﬂector

CuO cartridge (inside)

Started LAr ﬁlling on May 1st 2009 arXiv0904.0246 !"#$%&'($)*+)+$ 3/(453(

670%5"( LAr LAr blocked PMTsblocked Vacuum

Atmosphere

8=>?:%@76#(;ABCDE<( !"#$%&"'()*&(+%,(-(./(012&( Figure 40: The impedance doesn’t depend on the absolute pressure bevore the cartridge.

air drives the piston up and down. Both parts of the cycle are operated by overpressure. The actual behavior of the piston, how fast it should move is controlled by a bleed valve.

53 42 20th October 2008 Vittorio Boccone 3 A MeasurementPreliminary light setup Yield in ArDM DM 20th October 2008 Vittorio Boccone 5 !LY! Only vs.Light 6/8 positionPMTs yield working from infor GAr, α 5.3MeV(2 sourcesparking); !" !! 2 blue LEDs for calibration: blue LEDs UHV magnetic •! Mounted on a fiber and fixed near the Am source; actuator fiber •! Mounted on the flange;

!! Source/Fiber output can be moved by ±30cm from the central position; sufficient to see the decrease movable 241Am of the UV light detection for uncoated PMTs; source -30 !! Verify Light Yield dependence .

0 on the position of the event; !! Prepare measurement in . +30 Warm Cold liquid argon (1ton); X •!GAr P=1.1bar 1) ZD0051 - Evap - Side V• !GAr P=1.1bar reflectors with wavelength shifter •!T=300K 2) ZD0045 - TPB/PRL - Center •!T=88K cathode •!#2~2.8µs 3) ZD0038 - Clean - CenterX •!#2~3.7µVs e-shield •!LY values extrapolated to max 4) ZD0046 - TPB/PRL - Side •!Value are not extrapolated known purity # =3.2µs 2 5) ZD0050 - Evap - Center V photomultipliers 6) ZD0049 - Clean - SideV V Very good cold GAr purity (τtripletV ≈3.5-3.7µs) Conﬁrms effect of liquid phase trapping impurities 14 Tuesday, May 12, 2009 A Light measurement in liquid phase DM 20th October 2008 Vittorio Boccone 3 StatusMeasurement: May 8th 2009 - setupcompleted vessel ﬁlling !

!! Onlyα 6/8source PMTs working submersed in GAr, (2 sparking); with liquid !! 2 blue LEDs for calibration: blue LEDs τtriplet≈3.5µs(GAr)➠1.5µs(LAr) UHV magnetic •! Mounted on a fiber and fixed near the Am source; actuator fiber •! Mounted on the flange;

0 on the position of the event; !! Prepare measurement in . +30 liquid argon (1ton); X V reflectors with wavelength shifter cathode X V e-shield V photomultipliers V ArDM-1tV V Preliminary 15 Tuesday, May 12, 2009 The XENON100 Experiment at LNGS Columbia, Coimbra, LNGS, Münster, Rice, Subatech, UCLA, Waseda, Zürich

• Dual-phase, Xe-TPC to search for WIMPs by their collision with Xe-nuclei • 170 kg (100 kg in active veto) LXe, viewed by 242 low-BG PMTs, 30 cm ∅, 30 cm drift • Goal: mass x 10, background x 1/100 with respect to XENON10 • Status: under commissioning at LNGS, expected to start science run in 2009 • Expectation: test WIMP-nucleon cross sections of 2x10-45 cm2 after 6000 kg days Abstract by Laura Baudis, UZH

Columbia student LNGS student

UZH postdoc UZH postdoc XENON100 in its shield

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Status of XENON100

• Several calibration runs with LEDs and external sources • Short background runs (BG at the level predicted by Monte Carlo simulations, based on 238U/228Th/40K/60Co/137Cs data from screening of all XENON100 materials and shields) • Currently improving light yield; achieved so far ~ 2.7 p.e./keV; prediction is ~ 3.5 p.e./keV • Neutron calibration, then WIMP search run starting in the fall of 2009

Light yield in Run 5; now Run 6 started after several measures to reduce outgassing and improved sealing of detector

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Next step: The Xenon100 Upgrade

• 100 kg ﬁducial mass (total of 260 kg LXe), background 5x10-4 events/(kg day keV) • New photon detectors, QUPIDs; ultra-low BG Cu cryostat, new shield, including muon veto • Larger collaboration: Europe, US, Japan, China • Construction 2010; WIMP search 2011-2012; goal: 2x10-46 cm2 photocathode • NSF funding approved; SNF proposal submitted in March 09 quartz (-6 kV)

Al coating

APD (0 V)

quartz QUPID

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Next-to-Next Step: XENON1t

• Studies in progress for 3 ton (1 ton ﬁducial) LXe-TPC; 4π QUPID coverage • Possible locations: LNGS or ULISSE extension of the Modane Laboratory • Construction: 2012; WIMP search: 2013-2015; goal ~ 2x10-47 cm2 after 1t x year

• Possible CERN Involvements:

1m • cryogenic and liquid xenon puriﬁcation system? • the HV system? • the electronics/DAQ system? • ultra-low background Cu cryostat and/or shield? • use p/n/µ beams to study production rate of radioisotopes in LXe

Proposal for R&D and design study for ton-scale LAr/LXe detector in response to ASPERA call is being prepared by European ‘noble liquid 1m community’ (Germany, France, Italy, Poland, Switzerland) Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Dark matter search with bubble chambers Abstract by Antonino Pullia

• Superheated liquid -> detects single bubbles induced by high dE/dx nuclear recoils; advantage: large masses due to mechanical simplicity of detectors, low costs, SD, SI (I, Br, F, C) couplings, high 10 spatial granularity, ‘rejection’ of ERs 10 at 10keVr; challenge: reduce alpha background • Two important news: ➡ indeﬁnitely long stability in moderately superheated bubble chambers can now be reached (J. Bolte, NIM A577, 569 (2007)) ➡ different degrees of the superheated state correspond to different sensitivity for different particles (now better demonstrated than 40 years ago) • Three different techniques for dark matter searches: continuously sensitive bubble chambers, the Geyser detector, superheated droplets detectors • EXAMPLE: the COUPP experiment (Univ. of Chicago, FNAL)

n-induced 2 kg detector at 300 mwe in 2006: α BG from walls event 222Rn decays -> 210Pb plate-out + 222Rn emanation (multiple run with 2 kg in 2007/2008 (reduced backgrounds) scatter) best SD limit for MWIMP ≤ 30 GeV (pure p-couplings), Science 319 (2008) WIMP: single scatter 60 kg module under construction at FNAL with the goal of reaching 3 x 10-8pb

Tuesday, May 12, 2009 The GEYSER detector

• Principle of operation (B. Hahn and H.W. Reist-Berna, 1973, P. Negri et al., Milano-Bicocca 2009)

➡ A liquid is brought into a metastable state and kept at a temperature T2 = 30 C by a thermal bath

➡ The vapor above the liquid is kept at T1 = 20C < T2, by water cooling of glass bottle neck

➡ The equilibrium vapor pressure above the surface is p1 and the entire system is under p1 (the equilibrium pressure for the liquid should be p2 > p1) ➡ When energy is released locally (nuclear recoil), a bubble is created, becomes supercritical and grows to a large size, pushing the liquid into the bottle neck

➡ The pressure increases and when it reaches its equilibrium value at T2, the liquid returns into the main volume and the hot vapor in the neck re-condenses ➡ The metastable state is automatically recovered in a time scale ≈ few seconds • This project (Milano-Bicocca, INFN, CERN, Torino, Berne) has the following phases: ➡ construction of small scale prototypes (Geyser and bubble chamber), with traditional liquids (Propane, Freon etc); investigation of scintillating properties of these liquids (CF4 scintillates at 150-500 nm, with 1500 photons/MeV); Xe, Ar work as bubble chambers and scintillate ➡ choice of technique with best performance ➡ design of a larger scale detector (1 m3) ➡ the construction of a Geyser is in progress

Tuesday, May 12, 2009 Goals and comparison with COUPP

• A new technique (Geyser or Bubble chamber) with scintillating properties is investigated • Advantage of Geyser: the dead time is strongly reduced • Advantage of Bubble Chamber: larger ﬁnal masses could be reached (1-2 tons) • Advantage of scintillation: discrimination against alpha background ➡ Reduction of neutron background by underground operation and active n-shield (Gd, or Cd doped) ➡ Use ultra low-radioactivity materials ➡ Construct and operate a Geyser ➡ Study mechanical design for Larger Bubble Chamber (≈ 1 m3)

• Requests to CERN ➡ Support for use of scintillation liquid ➡ Collaboration with experts in the bubble chamber construction ➡ Very small part of laboratory for possible tests at CERN

Tuesday, May 12, 2009 The GERDA Experiment Belgium, Germany, Italy, Poland, Russia, Switzerland

Abstract by Laura Baudis, UZH • Goal: detect the neutrinoless double beta decay in enriched 76Ge detectors • Operate detectors in LAr (cooling medium and shield against external backgrounds, 63 m3) • Phase I: 18 kg (of existing) 76Ge detectors; exposure: 30 kg years • Sensitivity reach:

0ν 25 T1/2 > 3.0 × 10 yr

mνe < 0.27eV • Phase II: 40 kg enriched 76Ge detectors • Sensitivity reach after 150 kg years:

0ν 25 T1/2 > 15 × 10 yr

mνe < 0.11eV detector array GERDA LAr cryostat

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 Status of GERDA (April 2009)

• Double walled, stainless steel LAr cryostat, water tank, superstructure, electrical system and clean room installed at LNGS

• Phase-I detectors have been tested in the GERDA Detector Lab at LNGS

• Lock and gas handling system, as well as muon veto under installation

• Detector commissioning planned for fall 2009 • Concomitantly: R&D effort for phase II detectors (18-fold segmented, n-type and/or BEGe p-type)

Possible CERN involvement in GERDA phase-II (and III ?): water tank and super structure ➡ R&D and production of 76-Ge detectors? ➡ use p/n/µ beams to study production rate of radioisotopes in Ge and LAr

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009 END

Laura Baudis, University of Zurich, CERN New Opportunities Workshop, May 2009 Tuesday, May 12, 2009