Double beta search : experimental view Laurent SIMARD, LAL - Orsay 6 th Rencontres du Vietnam, Hanoi, 6 th -12 nd August 2006

 (0 ) : 2n  2p+2e -  L = 2 Process  Majorana Neutrino  and effective mass  Right-handed current in weak interaction  Majoron emission  SUSY particle exchange WW n n p p ee ee M (Q  ~ MeV) ( ) WW eR eL h h Double beta  (0 ) decay: Physics beyond the standard model A= xPSx IM I 2 2 Nuc.

Both techniques are complementary and at least 2 or 3 experiments are needed to really prove the 0 decay at a level of 5  Modest energy resolution and efficiency Large detector  a few 10 m No signature of the 2 electrons Only 1 observable: total energy Very high energy resolution Good efficiency « Compact » detectors (size  10 m) Crystals very pure (surface contamination ?) Direct signature of the 2 electrons 3 observables: - total deposited energy - individual energy - angular corelation Possibility to measure various isotopes Experimental approaches Calorimeter HPGe, Cd – Te bolometers Tracking + calorimeter NEMO,EXO

PURE CALORIMETER

The GERDA project (LNGS) - operate with “naked” Ge diodes in a very pure liquid nitrogen shielding (LN 2 ) - possible upgrade with liquid argon(LAr) for active anticoincidence from the scintillation light of LAr - segmentation of diodes for a greater reduction of backgrounds The MAJORANA Project in the US 210 HPGe segmented diodes in a standard shielding (500 kg of enriched 76 Ge) Phase III ~ 100 kg Segmented crystals Liquid Argon 10 years of data-taking Phase III /(keV·kg·y) /(keV·kg·y) /(keV·kg·y) Phase I ~ 15 kg 76 Ge (crystals Heidelberg-Moscow + IGEX) Phase I (2008) Phase II ~ 35 kg 76 Ge Segmented crystals 3 years of data-taking Phase II (2010) start with 60 kg

New detectors for Phase II: Procurement of enriched Ge March ’05: procurement of 15 kg of natural Ge (‘test run’) Sep ’05: enrichment of 37.5 kg of Ge-76 completed ! ~ 88% Ge-76 April ’06: enriched material transported to Germany; now stored underground at HADES Specially designed protective steel container reduces activation by cosmic rays by factor 20

Backgrounds in GERDA SourceB [10 -3 cts/(keV kg y)] Ext.  from 208 Tl ( 232 Th) <1 Ext. neutrons<0.05 Ext. muons (veto)<0.2 Int. 68 Ge (t 1/2 = 270 d)12 Int. 60 Co (t 1/2 = 5.27 y) Rn in LN/LAr< Tl, 238 U in holder<1 Surface contam.< days exposure after enrichment days underground storage 30 days exposure after crystal growing Target for phase II: B  cts/(keV kg y)  additional bgd. reduction techniques derived from measurements and MC simulations Muon veto

Background reduction techniques Muon veto Anti-coincidence between detectors Segmentation of readout electrodes (Phase II) Pulse shape analysis (Phase I+II) Coincidence in decay chain (Ge-68) Scintillation light detection (LArGe)

130 Te

Goal:  (  ) of 130 Te ~ 1000 TeO 2 bolometers Q  ~ 2.5 MeV Experimental data and simulations suggest one major contribute for CUORE background in the DBD region:  and  degraded particles emitted by 238 U and 232 Th surface contaminations on the Cu frame and on the crystal surface. BKG = 0.18 ± 0.01 c/(keV kg y) T 1/2  > 2× % C.L. Cuoricino   130 Te TeO 2 Cu TeO 2 CUORE : 130 Te in LNGS (760 kg of Te) If background = 0.01 cps/ (keV.kg.year) T 1/2 (  )  2.1 x years (90% C.L.) If background = cps/ (keV.kg.year) T 1/2 (  )  6.6 x years (90% C.L.) If background = cps/ (keV.kg.year) + enriched crystals T 1/2 (  )   1.9 x years (90% C.L.) After 5 years of data taking FWHM = keV Predictions on the future background expected for CUORE from Cuoricino background analysis and Monte Carlo simulations...

Surface Sensitive Bolometers Surface Sensitive Bolometers Background reduction may be achieved through both passive and active methods Creation of a new kind of detectors able to recognize surface events Identification of background events S urface S ensitive B olometers Auxiliary bolometer Main bolometer SSB Classic pulse High and fast pulse Dynamic behavior: Event originating inside the main bolometer (DBD event) Event originating outside the main bolometer (degraded  ) The difference between heat capacities generates a difference in pulse height and shape... Idea: cover each face of a classic bolometer by gluing an active layer, in order to provide a 4  shielding

First SSB experimental results (Como) First SSB experimental results (Como) Amplitude comparison According to the described dynamic behavior, various pulse parameters proved to be effective in discriminating surface events. (Scatter plot) -Individual thermistor read-out -Parallel thermistors read-out  r on auxiliary thermistor Bulk events Surface events Pulse amplitude on auxiliary NTD [mV] Pulse amplitude on main NTD [mV]  d on main thermistor Surface events Bulk events Pulse amplitude on main NTD [mV] Pulse amplitude on auxiliary NTD [mV] (To be investigated)

14.OUTGASSING 15.REACTIVE CLEANING: Anodic Oxidation and subsequent removal of the oxide 16.OZONE CLEANING 17.HYDROGEN CLEANING 1.ABRASIVE CLEANING, GRINDING and MECHANICAL POLISHING 2.SOLVENT CLEANING: Chlorofluorocarbons and Liquid CO2 3.SEMI-AQUEOUS CLEANERS: Terpenes; Alcohols; Ketones; Esters; Amines 4.ULTRASONIC CLEANING 5.MEGASONIC CLEANING 6.SAPONIFIERS, SOAPS, AND DETERGENTS 7.WIPE-CLEAN 8.SUPERCRITICAL FLUIDS 9.CHEMICAL ETCHING 10.ELECTROCHEMICAL POLISHING 11.ELECTROLESS ELECTROLYTIC CLEANING 12.DEBURRING: laser vaporization, thermal pulse flash deburring 13.STRIPPABLE COATINGS 18.REACTIVE PLASMA CLEANING AND ETCHING 19.PLASMA CLEANING 20.SPUTTER CLEANING 21.ION BEAM CLEANING THE POLISHING SYSTEM

The CANDLE project Prototype CANDLE III is in construction Osaka-JAPAN Pure CaF 2 crystals 10 3 cm 3 (scintillation) Energy resolution: ~ 4.2 MeV CANDLES III: 60 crystals : Total mass = 191 kg Crystals natural Calcium ~ 300 g of 48 Ca Technique could be very promising with enriched 48 Ca crystals Need to enrich ~ kg of 48 Ca !...

TRACKING + CALORIMETER

THE EXO PROJECT TPC with Xenon : possibility to use a large mass of isotope Xe noble gaz : centrifugation -> 200 kg of 130 Xe avalaible in Stanford T ½  very high Identification of Ba ion : 136 Xe  136 Ba ++ +2e - by laser fluoresence Difficulty: neutralisation Ba ++  Ba + collection of ions Phase 1: EXO-200, 200 kg of 136 Xe TPC with liquid Xe, detection of scintillation (FWHM ~ 2.5 MeV) No identification of the Ba + ion Start foreseen end 2007 Expected background : cts.keV -1.kg -1.y -1 T ½ > y With identification of the Ba + ion and 1 ton of 136 Xe Expected background < cts.keV -1.kg -1.y -1 Date ? T ½ > years

3 m 4 m B (25 G) 20 secteurs Source : 10 kg of  isotopes cylindrical shape, S = 20 m 2, e ~ 60 mg/cm 2 Tracking detector : wire chamber in Geiger regime (6180 cells) Gas: He + 4% ethylic alcohol + 1% Ar + 0.1% H 2 O Calorimeter : 1940 plastic scintillators coupled to low-radioactivity PMTs Magnetic field : 25 Gauss Gamma shielding : Iron (e = 18 cm) Neutron shielding : 30 cm water (ext. wall) 40 cm wood (top and bottom) (since march 2004: borated water) Able to identify e , e ,  et  The NEMO3 detector Frejus Underground Laboratory (LSM) : 4800 m equivalent water

82 Se

Preliminary results of NEMO-3 Phase I (with radon) February September 2004 : 298 days of data taking Phase II (without radon) December March 2006 : 290 days of data taking 100 Mo, 7 kg 82 Se, 1 kg T 1/2 (  ) > (90 % C.L.) T 1/2 (  ) > (90 % C.L.) T 1/2 (  ) > (90 % C.L.)T 1/2 (  ) > (90 % C.L.) Expected in 2009 Phases 1+2

NEMO-3 SuperNEMO T 1/2 (  ) > ln2  M    T obs N excluded N avo A  7 kg 100 kg Isotope mass M Efficiency   (  ) = 8 %  (  ) = 25 %  ~ 2 evts / 7 kg / y   ~ 1 evt / 100 kg/ y Background Internal contaminations 208 Tl and 214 Bi in the  foil 214 Bi < 300  Bq/kg 208 Tl <   Bq/kg 214 Bi < 10  Bq/kg 208 Tl <   Bq/kg ( 208 Tl, 214 Bi) ~ 1 evt/ 100 kg /y( 208 Tl, 214 Bi) ~ 1 evt/ 7 kg /y T 1/2 (  ) > y < 0.3 – 1.3 eV T 1/2 (  ) > y < 0.05 – 0.1 eV Energy resolution From NEMO-3 to SuperNEMO

Shielding : Water aganist  and neutron Source foil 5,7 m 13 m 4 m New cavity ~ 70m x 15m x15m ~ tons of water for 20 modules View of the detector in its shielding : construction of the 1 st module 2010: commissioning of the 1 st module measurement of the background level 2010 – 201N: construction of the other modules 201N: full detector

Which isotope for SuperNEMO ? High phase space factor Favorable nuclear matrix element… but uncertain calculations… High Q  for the background rejection Possibility of enrichment !... Choice criteria for the isotope: Phase space factor Nuclear matrix element Uncertainties from the theoretical calculations Effective mass of the Majorana neutrino = G  M  ‹m › 2 2  T 1/2 1 Half-life of the  decay

Which isotope for SuperNEMO ? IsotopeQ  (MeV)G  (an-1) Shell Model QRPA 48 Ca Ge Se Zr Mo Cd Te Xe Nd T 1/2 (  ) with m =50meV With QRPA nuclear matrix elements calculations, 100 kg of 150 Nd is equivalent to: ~ 340 kg of 82 Se ~ 720 kg of 130 Te ~ 1010 kg of 76 Ge ~ 2640 kg of 136 Xe  M 0  2 ? But value of  M 0  2 ? Shell Model: Caurier et al. QRPA: Faesller Rodin Simkovic Vogel 2005 Only phase space factor (M  =1) 100 kg of 150 Nd is equivalent to: ~ 410 kg of 82 Se ~ 410 kg of 130 Te ~ 1700 kg of 76 Ge ~ 400 kg of 136 Xe

Enrichment of  isotopes 82 Se: 100 kg in 3 years in ECP Zelenogorsk (Siberia) price ~ 50 keuros / kg Agreement for 1.5 kg (ILIAS funding) Enrichment by centrifugation: SILVA Infrastructure in Pierrelate (France) In 2003: enrichment of 200 kg of 235 U in 2 weeks ! 235 U + 3 photons  235 U + + e  Possibility of enrichment of 200 kg of 150 Nd in few weeks ! Simulations done par Alain Petit (DEM, CEA) Enrichment of 96 Zr and of 48 Ca could be considered : to be studied… Main goal : maintain the installation for an enrichment of 100 kg of 150 Nd  “Statement” of the SuperNEMO collaboration Enrichment by laser photoionisation

Sensibility of SuperNEMO : discussion  Simulation Monte Carlo with 5 years of data taking  82 Se T 1/2 > years mais constrain on 214 Bi, Radon et 208 Tl are very strong  150 Nd T 1/2 > years equivalent to y ( 82 Se) because of the phase space factor.  background similar for 82 Se whereas T 1/2 is lower (Fermi factor : coulombian effect due to the high Z) No constraint on 214 Bi and radon (Q  = MeV)  48 Ca T 1/2  years equivalent to y ( 82 Se) because of the phase space factor. No constrain on 214 Bi and radon Constrain on 208 Tl much less stronger (Q  = MeV) 150 Nd: T 1/2 (  ) = y 82 Se: T 1/2 (  ) = y

ExperimentNucleusMass (kg) FWHM at Q  (keV) Background Counts/ fwhm.kg.y T 1/2 (  ) limit (years) limit (meV) Starting taking data NEMO 3 CUORICINO 100 Mo 82 Se 130 Te ~ 0.5 ~ 0.1 ~ – – 850 GERDA Phase 1 Phase 2 Phase 3 76 Ge – – – ? SuperNEMO 82 Se 150 Nd – CUORE if enrich mt 130 Te nat Te 130 Te – – ? CANDLES III if enrich mt 48 Ca nat Ca 48 Ca – ? EXO-200 EXO Ba + tag 136 Xe – – ? Nuclear Matrice elements: Shell Model: Caurier (2004) private com. Stoica et al. (2001) Suhonen et al. (1998 and 2003) QRPA Rodin, Simkovic, Faessler (2005) Expected sensitivities COBRA 116 Cd 418<56<0.001 ~10 26 ? ~

Constrain on Cosmology Current experiments Next generation (Figure from C. Giunti)

 Cuoricino and NEMO3 are running ~ for 5 years : range ≈ a few 100 meV  R&D for new experiments with a mass of ≈ 100 kg of enriched isotopes. aim : a few 10 meV with at least 3 isotopes  Coordination in Europe (ILIAS)  Neutrinoless double beta decay could be one of the experimental key for understanding neutrino physics : it is a long way but promising ? Conclusion

Radon in the NEMO-3 gas of the wire chamber Due to a tiny diffusion of the radon of the laboratory inside the detector A(Radon) in the lab ~15 Bq/m Rn (3.8 days) 218 Po 214 Pb 214 Bi 214 Po 210 Pb    s ~ 1  -like events/year/kg with 2.8 < E 1 +E 2 < 3.2 MeV Two independent measurements of radon in NEMO-3 gas Good agreement between the two measurements  Radon detector at the input/output of the NEMO-3 gas ~ 20 counts/day for 20 mBq/ m 3  (1e  + 1  ) channel in the NEMO-3 data: Delayed tracks (<700  s) to tag delayed  from 214 Po 214 Bi  214 Po (164  s)  210 Pb ~ 200 counts/hour for 20 mBq/m 3 A(Radon) in NEMO-3  mBq/m 3 Decay in gas  delayed  214 Bi  214 Po (164  s)  210 Pb   Radon was the dominant background for  0 search in NEMO-3

May 2004 : Tent surrounding the detector Free-Radon Purification System 1/2

Starts running Oct. 4 th 2004 in Modane Underground Lab. 1 ton -50 o C, 7 bars Activity: A( 222 Rn) < 15 mBq/m 3 !!! Flux: 125 m 3 /h a factor 1000 Free-Radon Air factory

Time (days) Level of radon measured inside the wire chamber, by analysing (1e  + 1  ) channel in the NEMO-3 data Without tent: A ~ 1.5 Bq After flushing radon-free air inside the tent: A ~ 0.15 Bq Radon level reduced by a factor of 10 Residual level to be understood sources ? Thanks a lot to S.K especially M.Nakahata,S.Tasaka Radon level inside the detector - Results -

The double beta process Allowed process  2 if m    0 and    double beta  0 Q  : end-point energy ~ 2-4 MeV Experimentally : a peak for The energy sum of the 2 e - Arbitrary scale E/Q 

Two different approaches PURE CALORIMETER only measurement of the energy sum of the 2 e - Esum high efficiency high precision for the measurement of Esum BUT sensitive to an unknown gamma line Semi-conductors : GERDA,MAJORANA (Ge) CANDLE (Cd,Te) Bolometer : CUORICINO/CUORE TRACKING+CALORIMETER identification of the 2 e - measurement of the 2 electrons energies, and of the angular distribution measurement of each background amount BUT reduced efficiency and energy resolution NEMO/SuperNEMO, EXO IDENTIFICATION OF THE NATURE OF THE PROCESS (Majorana, right current…)

GERDA : 76 Ge in LNGS Vacuum insulated Copper or steel vessel Water tank / buffer/ muon veto Liquid N/Ar Ge Array Phase I : 17.9 kg of enriched Ge-detectors underground at LNGS (from IGEX and Heidelberg-Moscow) HdM IGEX