Direct Dark Matter Searches

Direct Dark Matter Direct Dark Matter SearchesSearches

Véronique SANGLARDUCBL-CNRS/IN2P3/[email protected]

V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05 2

Outline

Motivations for non-baryonic dark matter search

Principle of the direct detection Running experiments Future experiments Conclusion


Motivations for Dark Matter Search (1)

Rotation curves studies

Dark matter halo around the galaxies

Local density : 0.3 GeV/cm3


Motivations for Dark Matter Search (2)

At cosmological scale :Results of WMAP ->

Ω tot ~ 1.00 Ω baryon < 0.05 (confirmed

by experiments like EROS, MACHO)

Ω matter ~ 0.3 Ω Cold Dark Matter ~ 0.22

Need weakly interacting non-baryonic massive particles …

WIMP (σ<10-6 pb)


CDMS

Natural WIMP candidate0 01 2Z H H

Neutralino definition in the SUSY field Stable particle if R-parityconserved (LSP)

Indirect detection : Detection of WIMPs annihilation

products

Direct detection : Detection of WIMPs scattering off nuclei

SUPER K

ANTARES

DAMAEDELWEISS

AMANDA

ZEPLIN


Direct Search Principle Detection of the energy deposit due to elastic scattering on

nuclei of detector in laboratory experiment

Optimum sensitivity for MWIMP ~ MRECOIL Rate < 1 evt/day/kg of detector

Need low background Deep underground sites Radio-purity of components Active/passive shielding

Need large detector mass (kg -> ton) Recoil energy ~ 20 keV

Need low recoil energy threshold


WIMP signatures Nuclear recoils

Not electron recoils (dominant background) Neutron scattering also produces recoils …

spectrum shape Exponential (as most bkg) Shape for backgrounds : unknown/poorly predicted

Coherent interaction (Spin-independent) ? Absence of multiple scattering (against neutron) Uniform rate throughout volume (against surface

radioactivity) Directionality of nuclear recoils Annual rate modulation

recoil

dNdE

2 2A A


Direct detection techniquesWIMP

Heat

Ionization

Light

Ge

Liquid Xe

NaI, Xe

Ge, Si

CaWO4, BGO

Al2O3, LiF

Elastic nuclear scattering

1% energyfastestno surface effects

10% energy

100% energyslowestcryogenics

WIMP

Target


Current direct detection experiments

CUORICINO Gran Sasso Heat 41 kg TeO2 runningGENIUS-TF Gran Sasso Ionization 10 to 40 kg Ge in N2 running ???

HDMS Gran Sasso Ionization 0.2 kg Ge diodes stoppedIGEX Canfranc Ionization 2 kg Ge Diodes stopped

DAMA Gran Sasso Light 100 kg NaI stoppedLIBRA Gran Sasso Light 250 kg NaI runningNaIAD Boulby mine Light 46 kg NaI stopped

ZEPLIN-I Boulby mine Light 4 kg Liquid Xe stoppedXENON Surface to GS Light+ Ionization 3 to 10 kg Liquid Xe running

ZEPLIN II Boulby mine Light+ Ionization 6 kg Liquid Xe runningCDMS-I Stanford Heat + Ionization 1 Kg Ge + 0.2 Kg Si stoppedCDMS-II Soudan mine Heat + Ionization 2 to 7 kg Ge + 0.4 to 1.4

Kg Sirunning

CRESST-I Gran Sasso Heat + Light 0.262 kg Al2O3 stoppedCRESST-II Gran Sasso Heat + Light 0.6 to 9.9 kg CaWO4 running

EDELWEISS-I Modane Heat + Ionization 1 kg Ge stoppedEDELWEISS-II Modane Heat + Ionization 10 to 30 kg Ge In istallation

PICASSO SNO Bubble chamber 20 g Freon runningROSEBUD Canfranc Heat + Light 50 g Al2O3 + 67 g Ge + 54

g CaWO4

running

Discrimination

Name Location Technique Material Status

Even

t-by-

even

tSt

atisti

cal

None


NaI scintillation : DAMA Based in Gran Sasso lab (3500

mwe) 100 kg of NaI(Tl) Exposure : 107731 kg.d Coincidence between 2 PMTs Pulse shape rejection inefficient at 2

keVee Used annual modulation Claim annual modulation at 6.3σ

over 7 annual cycles Mχ ~ 52 GeV/c² σn ~ 7.2 10-6 pb

Not compatible with CDMS, EDELWEISS experiments

Future = LIBRA (250 kg of NaI)

NaINaINaINaI

PMT

PMT


NaI scintillation : DAMA Based in Gran Sasso lab (3500

mwe) 100 kg of NaI(Tl) Exposure : 107731 kg.d Coincidence between 2 PMTs Pulse shape rejection inefficient at 2

keVee Used annual modulation Claim annual modulation at 6.3σ

over 7 annual cycles Mχ ~ 52 GeV/c² σn ~ 7.2 10-6 pb

Not compatible with CDMS, EDELWEISS experiments

Future = LIBRA (250 kg of NaI)Single-hits events residual rates


Ge ionization : GENIUS-TF Based in Gran Sasso lab

(3500 mwe) Running experiment 4x2.5 kg (up to 14) naked

HPGe in N2 Problems surface

contamination by Radon Goal for background :

1 count/(kg.keV.y) < 50 keV But serious problems for

GENIUS (1T of Ge in N2)


Liquid Xe Scintillation : ZEPLIN-I Based in Boulby mine

(2800 mwe) 3.2 kg (fid.) -> 230 kg.d Single phase 3 PMTs coincidence Pulse Shape Amplitude (time

constant discrimination) Difficulties with neutron

calibration at low energy (in deep site)

Resolution 100% at 40 keV (7 keVee)

Experiment now completed but no published results yet

Future : ZEPLIN II (30 kg) Ionization+scintillation

Xe*

+Xe

Xe2*

Triplet27ns

Singlet3ns

2Xe2Xe

175nm

Xe** + Xe

Xe2+

+e-

(recombination)

Xe+

+XeIonization

Excitation

Electron/nuclear recoil

175nm


Liquid Xe Scintillation+Ionization : XENON

Prototype 3kg (active mass) dual phase detector with TPCs

7 PMTs in the cold gas above the liquid

Measurements of Primary scintillation light (S1) Secondary scintillation light

from ionization electrons (S2) CsI photoelectron signal (S3)

Discrimination variable S1/S2 Current work

Calibrations (γ, α, neutrons) Future : XENON10,100,1T in

Gran Sasso lab

S1 S2 S3


Liquid Xe Scintillation+Ionization : XENON

Prototype 3kg (active mass) dual phase detector with TPCs

7 PMTs in the cold gas above the liquid

Measurements of Primary scintillation light (S1) Secondary scintillation light

from ionization electrons (S2) CsI photoelectron signal (S3)

Discrimination variable S1/S2 Current work

Calibrations (γ, α, neutrons) Future : XENON10,100,1T in

Gran Sasso lab

Simulation ofdetector response

for neutron calibration

Electronic recoils

Nuclear recoils

First plot showing neutron calibration with Liquid Xe


Phonon and scintillation/ionization

bolometers Simultaneous

measurement of phonon and scintillation/ionization

Different (light or charge)/heat ratio for nuclear and electron recoils (WIMP and neutron have lower light/charge than γs, βs )

Discrimination event-by-event of electron recoils (main background)


Heat-scintillation : CRESST-II Based in Gran Sasso lab

(3500 mwe) 2x300g CaWO4 crystal

+W-SPT Net exposure: ~ 20.5 kg.d Rejection at 15 keV: 99.7% No neutron shield installed WIMP interact mainly with W Energy range: 12-40 keV

separate cryogeniclight detector

W SPT(W-Superconducting

Transition Thermometers)absorber :


Heat-scintillation: CRESST-II

90% of nuclear recoilswith quenching factor Q=7.4 below this line

90% of nuclear recoils with Q=40 (W) below this line

0 events (between 12 and 40 keV)Only this detector used to derive exclusion limits


Heat-ionization: CDMS-II Based in Soudan

Underground lab (2090 mwe)

4x250g Ge + 2x100g Si

Net exposure: 19.4 kg.d Detector = ZIP

(sensitive to athermal phonon)

Active muon veto + shielding (PE + Pb)

ZIP 1 (Ge)ZIP 2 (Ge)ZIP 3 (Ge)ZIP 4 (Si)ZIP 5 (Ge)ZIP 6 (Si)

SQUID cards

FET cards

4 K

0.6 K0.06 K0.02 K

Q inner

Q outer

A

B

D

C

Rbias

Ibias

SQUID array Phonon D

Rfeedback

Vqbias


Heat-ionization: CDMS-II Rejection of background surface events with timing

cuts

0 events (between 10-100 keV)


Heat-ionization: EDELWEISS-I Based in Modane Underground

laboratory (4800 mwe) Low radioactivity dilution

cryostat at 17 mK Shielding : PE+Pb+Cu 3x320g Ge

Amorphous layer (Ge/Si) NTD Ge thermometric sensor Al electrode (one segmented) Fiducial volume: 57%

Rejection-γ 99.9% at 15 keV3x320g heat-and-ionizationGe cryogenic detectors


Heat-ionization: EDELWEISS-I New data taking with trigger

on phonon signal Improved efficiency at low

energy (50 % at 11 keV) Fiducial exposure: 22 kg.d Stable behavior over 4

months 18 nuclear recoil candidates

> 15 keV 1 n-n coincidence Possible backgrounds

Residual neutron flux Miscollected charge events

Not enough statistics to conclude


Heat-ionization: EDELWEISS-I Final results: 62 kg.d (fid. exp.) 50% trigger efficiency at 15 keV 40 nuclear recoil candidates > 15 keV

(only 6 > 30 keV) Unknown background

Used method developed by S. Yellin to derive exclusion limits (as CDMS)

No background subtraction New limits consistent with previous

published results

V.Sanglard et al. astro-ph/0503265 (to PRD) Experiment stopped in March 2004


90% C.L. exclusion limits on WIMP-nucleon scattering cross-section (spin-

independent)

Only publishedresults are reported


Next step for running experiments

CDMS-II 7 towers (=4x250g Ge + 2x100g Si) 2 running now

CRESST-II 33x300g CaWO4 Wiring to mK level New readout system Neutron shielding + μ veto

EDELWEISS-II Next slide


EDELWEISS-II Low radioactivity cryostat

with larger experimental volume (50 liters)

Improved neutron shielding Addition of μ veto 1st phase: 28 detectors

(21x320g Ge+7x400g NbSi) Up to 120 detectors Expected sensitivity:

0.002 evt/kg/day Installation in progress in

LSM


Conclusion Today: 10-6 pb era

Starting to test most optimistic SUSY models

Next step: 10-8 pb Increased detector mass Further reduce background

rejection Lower energy threshold Improve event-by-event

discrimination Goal: 10-10 pb within 10 years

Probe most of the allowed SUSY parameter space

1 ton scale (SuperCDMS, EURECA)

Combined several targets


Conclusion Today: 10-6 pb era

Starting to test most optimistic SUSY models

Next step: 10-8 pb Increased detector mass Further reduce background

rejection Lower energy threshold Improve event-by-event

discrimination Goal: 10-10 pb within 10 years

Probe most of the allowed SUSY parameter space

1 ton scale (SuperCDMS, EURECA)

Combined several targets


1 ton : a simple experiment ?

Documents

Direct Dark Matter Searches