Looking for WIMPs with EDELWEISS Results and status of EDW I Prospects for EDW II + DAMA /LIBRA: brief status/future G. Gerbier CEA/Saclay/DAPNIA G. Gerbier NESS 2002 1
The Edelweiss Collaboration CEA- Saclay DAPNIA: G. Chardin, H. Deschamps, G. Gerbier, M. Gros, S. Hervé, A. de Lesquen, M. Loidl, J. Mallet,L. Mosca, X. F. Navick, F. Nizery, L. Shoeffel CEA- Saclay DRECAM: M. Chapellier, P. Pari CRTBT Grenoble: A. Benoit, M. Caussignac, H. Rodenas CSNSM Orsay: L. Bergé, A. Broniatowski, L. Dumoulin, A.Juillard, S. Marnieros, N. Mirabolfathi, S. Collin IAP Paris: C. Goldbach, M. Martin, G. Nollez IPN Lyon:A. Bonnevaux, B. Chambon, L. Chabert, M. De Jesus,P. Di Stefano, D. Drain, J. Gascon, E. Gerlic, M. Goyot, J. P.Hadjout, O. Martineau, V. Sanglard, M. Stern,L. Vagneron Laboratoire Souterrain de Modane:P. Charvin (1/2), C. Riccio (1/4) (out of 4 technicians / 1 secretary in Modane) Tech Univ Munich : J. Jochum, H. Wulandari EDELWEISS : Expérience pour DEtecter Les Wimps En ISte Souterrain TECNomSiQ: Team Edelweiss Cresst for Neutron and m Shield Qualification G. Gerbier NESS 2002 2
Fréjus Lab (LSM) Fréjus Underground Laboratory NB : 3300 m 3 ITALIE FRANCE TUNNEL ROUTIER DU FREJUS GRAND HALL NEMO III 3, 2 T EDELWEISS I et II 4800 m water eq. Muon flux 4 m/m 2 /day Neutron flux 1.6 10-6 s -1 cm -2 ( from rock radioactivity) G. Gerbier NESS 2002 3
EDELWEISS-I, 1kg stage Archeological lead 320 g Ge detectors G. Gerbier NESS 2002 4
1kg stage of EDELWEISS-I : 3*320 g Ge. GGA1: heat and ionisation Ge 320 gram detectord, 20 mm thick aluminium electrodes (center + guard ring) + Ge amorphous layer (made by Canberra/Eurysis Eurysis) NTD sensor on guard ring electrode +wiring in Saclay Low radioactivity cryostat Shield: : 30 cm paraffin,, 20 cm Pb,, 10 cm Cu Resolutions @ 10 kev (resp 122) kev: ionisation : 1.3 kev (2.2 kev) heat : 1.0 kev (3.0 kev) G. Gerbier NESS 2002 5
57 Co calibration. Charge collection Detector with amorphous Ge surface treatment Few miscollected surface events 99.99 % background rejection ( 60 Co) Other detectors no amorphous layer More miscollected events 97.8-98.7 background rejection ( 60 Co) G. Gerbier NESS 2002 6
Gamma rejection neutron calibration n/g discrimination 99.9% for Er >15 kev 73 Ge(n,n g) Recoil threshold 20 kev Ionization threshold 3.7 kev Q= G. Gerbier NESS 2002 7
54 days fl 15.1 kg.day net fl 8.6 kg.day fl 7.74 kg.day fl 7.4 kg.day EDELWEISS-I : 2002 data from GGA1 detector 12% dead time 54 % fiducial Volume 90%nuclear recoil acceptance Upper recoil energy limit 95 % efficiency (ex : 119 kev recoil M W =10 TeV) G. Gerbier NESS 2002 8
The result of perseverance 1997 13 evts/kg.d in nucl recoil zone 2000 2 evts/kg.d 2002 <0.3 evts/kg.d G. Gerbier NESS 2002 9
EDELWEISS-I 05/2002 Present sensitivity for spin independent WIMPs Same model, astrophysic and nuclear parameters as DAMA and CDMS M W = 52 GeV, s = 7.2x10-6 pb : fi Prediction = 9.8 evts, P(0) = 0.006% M W = 44 GeV, s = 5.4x10-6 pb : fi Prediction = 6.2 evts, P(0) = 0.2% Exploration of first sample of SUSY models compatible with accelerator constraints. ficurrently accumulating data with 2 GGA fitest and data taking with 2 GSA up to 03/2003 G. Gerbier NESS 2002 10
from EDELWEISS I 1kg Copper Detection volume 50l 20 cm lead shielding 10 layers of 12 detectors of 320 g 3 detectors of 320 g to EDELWEISS II 6kg, 36 kg He tank G. Gerbier NESS 2002 11
EDELWEISS-II detector setup (Phase 21*320g detectors : approved, 2004) Reversed cryostat for up to 120 detectors : 36 kg Ge Shield : 20 cm Pb + 50 cm PE Improve sensitivity by fact 100 => down to 2 10-8 pb Start installation in march 2003 G. Gerbier NESS 2002 12
Backgrounds Physical : localised in recoil zone : neutrons 1. Radioactivity from rock 2. Radioactivity from inside (U fission) 3. m interactions in shield 4. m interactions in rock Instrumental : not localised but «fall» in recoil zone g spill over (resolution) Ge 68 Surface events Incomplete charge collection Unexpected/unknow Protections 1. Outside : paraffin shield 2. Inside (fission) : PE shied or segmentation (multiple) 3. m VETO 4. m VETO Identification : multiple Protections Clean detectors (RA, radon, dust ) Surface event identification : ballistic phonon identification with thin films G. Gerbier NESS 2002 13
1) a n and fission in rock : calculations done by H. Wulandari at TUM (using MCNP) within TECNomSiQ -Due to U/Th in rock/concrete- LNGS Hall A B C Activities (ppm) 238 U 6.80 0.42 0.66 232 Th 2.167 0.062 0.066 FLUX in the LNGS Lab (10-6 n/cm 2 /s): 1-2.5 MeV 2.5-5 MeV 5-10 MeV Hall A, 8% water 0.35 0.18 0.05 Hall A, 16% water 0.18 0.12 0.03 Hall C, 8% water 0.27 0.15 0.03 Belli et al. 0.38 ± 0.01 0.27 ± 0.14 0.05 ± 0.01 Concrete 1.05 0.66 + composition of rock/concrete Calculation of neutron yield Neutrons from (a,n): Hall A rock: 4.38 n/y/g rock Hall C rock: 0.39 n/y/g rock Conc. (8% water): 0.50 n/y/g conc. E > 1 MeV neutrons come from : 7 cm concrete 13 cm rock Concrete thickness: 40 cm (up to 1m in some places in LNGS) CONCRETE MORE IMPORTANT!! and neutron spectrum G. Gerbier NESS 2002 14
a n and fission : the case of LSM (Fréjus lab) Rock Concrete Frac Fission/Tot Rate n/g/y Fission 0.44 1 a n (updated data on Ca 05/2002) 0.9 0.7 Total 1.34 1.7 35 % to 60 % Flux /cm2/sec > 1 MeV calculation Fission 2.2E-07 5.0E-07 a n 6.1E-07 4.7E-07 Total 8.3E-07 9.8E-07 25 % to 50 % Flux /cm2/sec > 1 MeV measured 1.60E-06 - slightly higher rates and flux than LNGS NB : TECNomSiQ= Team Edelweiss Cresst for Neutron and m Shield Qualification G. Gerbier NESS 2002 15
3) neutron flux from cosmic-ray muons +V.A. Kudryavtsev results (University of Sheffield) Tests of the FLUKA, MCNP, MUSIC, GEANT 3/4 simulation codes Characteristics to investigate and compare to existing measurements Neutron production rate as a function of muon energy (depth); Neutron production rate as a function of atomic weight of material; Neutron energy spectrum; Neutron flux as a function of distance from muon track. Comparison with experimental data => Tools exist, must be fine tuned for real DM experiments G. Gerbier NESS 2002 16
Neutron production as a function of m energy experiments in scintillator/lead LSD ASD LVD 3.7 10-3 /m/g/cm 2 Palo Verde 2.3 10-4 /m/g/cm 2 Parametrisation in scintillator Nn = 4.14 E m 0.74 10-6 /m/g/cm 2 Wang et al. Phys Rev D 64 (2001) 013012 Bergamasco et al, 73 Nn = 3.2 E m 0.78 10-6 /m/g/cm 2 VK (IDM 2002) G. Gerbier NESS 2002 17
A dependance of neutron production Simulation VK For Em= 280 GeV Nn = 5.3 A 0.76 10-5 /m/g/cm 2 Parametrisation VK IDM 2002 G. Gerbier NESS 2002 18
Note big difference in shape below 8 MeV Exp spectrum depends on shield set up Preliminary simulations of neutron production in Pb with GEANT 3 modified by KARMEN (Lyon) dn/de 10 7 10 6 10 5 10 4 1000 100 Neutron energy spectrum from muons in thick Pb slab 50100 cm Primary and outgoing neutron spectra GEANT 3 98 % Outgoing neutrons 98 % Primary neutrons 10 1 0.1 0.1 1 10 100 1000 Energy (MeV) G. Gerbier NESS 2002 19
1000 4) transformation by EDW2 shield of HE neutrons m rock in LE neutrons at detector level Neutron energy spectrum in lab from muons in rock + contribution to flux in 1-10 MeV window at detector level Dementyev spectrum 100 10 1 Flux /cm /sec/mev * 10-14 Neutrons contributing to flux at detector level e -d/0.9m 0.1 10 100 1000 Energy (MeV) G. Gerbier NESS 2002 20
Résumé : neutron spectra at EDWII detectors 1.00E-04 1.00E-05 1.00E-06 Neutron energy spectra at detector for the 4 sources arbitrary normalisation RA rock Fission U in lead Mu rock Mu lead 1.00E-07 1.00E-08 1.00E-09 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 E neutron MeV => Similar shapes e -(E/0.7) for E<5 MeV, except for rock RA-steeper G. Gerbier NESS 2002 21
Summary of neutron background flux estimations at EDELWEISS II detector Background source Radioactivity from Rock U fission in Pb of shield assuming 0.1 ppb Neutrons from muons in Pb shield Neutrons from muons in rock Predicted flux at detector after shield E > 1 MeV 0.4 10-10 n/cm_/sec 1 <1.2 10-10 n /cm_/sec <3 10 10-10 n /cm_/sec 25 1.7 10-10 n /cm_/sec 4 Predicted flux at detector after shield E > 0.5 MeV 1.2 10-10 n /cm_/sec <2.4 10-10 n /cm_/sec 20 10-10 n /cm_/sec 3.2 10-10 n /cm_/sec m VETO e = 95 % will reduce this too G. Gerbier NESS 2002 22
EDELWEISS II m Veto 38.4 kg Ge 4 m Karlsruhe/KARMEN group joins EDELWEISS and provides the m VETO =140 m 2 plastic scintillator G. Gerbier NESS 2002 23
Instrumental background Example of GeAl9 => incomplete charge collection «flat» distribution in Q vs E plane at Q<0.5 fithe 3 evts of GGA1 at Q <0.5 could be same origin at lower rate or physical origin (1 neutron, 1 recoil, 1 surface event) G. Gerbier NESS 2002 24
Edelweiss II 100 detectors exercice : 6 months live = 3000 kg.d exposure 80 GeV WIMP, 2 10-8 pb Expected neutrons «Flat» background reduced by fact 10/GGA1 95 % accept 80 GeV WIMP G. Gerbier NESS 2002 25
g s 241Am (60Kev,18kev,14kev) Surface event rejection Ballistic phonon detection with Nb Si thin layers Ge bolometer (35g) (heat & ionization) E=1.5 Volt/cm Thermometer A Thermometer B A/B amplitude ratio 6 4 2 0 50 Charge deficit for A/B>2.5 (near surface events) Charge deficite Amplitude ratio (UP/DOWN) Full charge collection for A/B<2.5 (bulk events) 100 150 200 250 Ionization(kev) (kev) G. Gerbier NESS 2002 26 300 350 Counts 80 60 Counts 40 20 0 0 Raw energy spectrum Spectrum cleared from near surface events (A/B<2.5) Histogram of Ionization before and after rejection Before After 20 40 60 Ionization(kev) Ionization (kev) 80 Allows to reject surface events down to the energy threshold 100
This is a real thing September 2002 : dilution OK Wiring and cold electronic test : end 2002 Mounting in LSM : 03/2003-03/2004 Data taking with 6 kg : mid 2004 G. Gerbier NESS 2002 27
Wimp search goals NB : 0 evt/10 kgd NB : 0 evt/30 kg/60d EDW2 NB : 0 evt/1ton/200d 1 Ton G. Gerbier NESS 2002 28
Costs Edelweiss program (no labor costs) From EDELWEISS I to EDELWEISS II-6 kg- 1998-2004 : 3.8 M Additional cost to go to 36 kgs : 2.8 M Infrastructure (LSM) 0.2 M /y 0.1 to 1 ton experiment Cryogenic? G. Gerbier NESS 2002 29
hep-ph/0112018 December 2001 DAMA astro-ph/0205047 May 2002 G. Gerbier NESS 2002 30
From DAMA to LIBRA G. Gerbier NESS 2002 31
Towards next step : 1 ton detector(s) in Europe - CRESST-II, EDELWEISS-II, ZEPLIN-II are test stages of the 10-30 kg level - should test approx. 10-8 picobarn sensitivity range - sampling the 10-9 -10-10 picobarn range is beyond our present detector knowledge Requires in any case experiments at the ton scale, one or two at European scale - CRESST, EDELWEISS and KARMEN starting to assemble a collaboration and common working groups to design this ambitious experiment EU is initiating ApPEC (Astroparticle Physics European Coordination). => (CRESST, EDELWEISS, Karlsruhe) +, ZEPLIN will most probably present a common bid to EU for common R&D, networking and design studies => goal: make a common design study for neutron background studies and protection, avoid to duplicate efforts, define the best two lines of research for discriminating experiments (most probably cryogenic detectors and Xenon at the one-ton scale) assuming no definitive systematic background or limitations appears at the 10-30 kg stage G. Gerbier NESS 2002 32