Neutrino Masses Dirac oscillations Majorana double beta decay

1) Oscillations: 2) Kinematics in weak decays: 3) 0 double beta decay:

Mainz frozen T 2 source, DE=4. 8 e. V Troitsk gaseous T 2 source, DE=3. 5 e. V Reported anomaly most likely experimental artifact

Katrin (Karlsruhe)

187 Re 187 Os + e - + e E 0=2. 5 ke. V, 43 Gyr, abundance 62. 8 % Milano: 10 Ag. Re. O 4 crystals (250 -300 g each) as cryogenic bolometers (T=10 m. K) DE(FWHM)=28 e. V at 2. 5 ke. V mn < 21. 7 e. V at 90 % CL

Double Beta Decay d(n) u(p) d(n) e ec ec eu(p) d(n) u(p) W W d(n) e- ec. R e. L eu(p)

d. N dt 0+ 2 c 0 0 (A, Z+1) (A, Z) 2+ e- e- E 0 0+ (A, Z+2) Eee E 0 (Me. V) Popular candidates 48 Ca 76 Ge 82 Se 82 Kr 100 Mo 100 Ru 128 Te 128 Xe 130 Te 130 Xe 136 Ba 150 Nd 150 Sm 232 Th 232 U 238 Pu Abundance (%) 4. 271 2. 040 2. 995 3. 034 0. 868 2. 533 2. 479 3. 367 0. 187 7. 8 9. 2 9. 6 31. 4 34. 5 8. 9 5. 6 dir dir, geo dir 0. 858 1. 145 100 99. 3 melking

76 Ge Heidelberg-Moscow (Gran-Sasso) 11 kg of 87 % 76 Ge in 5 crystals Energy [ke. V]

214 Bi 0 total 71. 7 kg yr SSE

2 direct geochem. direct Nucleus QRPA Caltech Shell model Strasbourg. Madrid exp 48 Ca - 0. 91 4. 3 x 1019 76 Ge 0. 71 1. 44 1. 8 x 1021 82 Se 1. 5 0. 46 8. 0 x 1019 100 Mo 0. 6 - 1. 0 x 1019 130 Te 0. 33 0. 35 6. 6 x 1020 128 Te 0. 27 0. 25 2. 0 X 1024 130 Te 0. 27 0. 29 8. 0 x 1020 136 Xe <1. 0 <2. 6 >8. 1 x 1020 Baksan

direct QRPA Shell model Caltech-Tübingen Strasbourg-Madrid -

Next experiments: large mass + low background, better signature, good energy resolution NEMO 10 kg of 100 Mo + … in tracking device Majorana 500 kg of 86 % enriched 76 Ge 10 cryostats with 21 crystals (2. 4 kg each) , segmented readout CUORICINO, 42 kg , 760 kg 130 Te, 56, 1000 crystals of Te. O 2, operated as CUORE bolometers (8 m. K) GERDA 0. 1, 1 t, 10 t of 76 Ge crystals, immersed in l. N 2 EXO 200 kg, 1 t, 10 t of 136 Xe in TPC

Enriched Xenon Observatory for double beta decay Alabama, Caltech, Carleton, Colorado, UC Irvine, ITEP Moscow, Laurentian, Neuchatel, SLAC, Stanford 136 Xe: 136 Ba++ e- e- final state can be tagged using optical spectroscopy (M. Moe PRC 44 (1991) 931) Much improved signature! 2 P 1/2 650 nm Ba+ 493 nm system best studied (Neuhauser, Hohenstatt, Toshek, Dehmelt 1980) Very specific signature “shelving” Single ions can be detected from a photon rate of 107/s 4 D 3/2 2 S 1/2 metastable 47 s

Isotopic enrichment for a gaseous substance like Xe is most economically achieved by ultracentrifugation Russia has enough production capacity to process 100 ton Xe and extract up to 10 ton 136 Xe in a finite time This separation step that rejects the light fraction is also very effective in removing 85 Kr (T 1/2=10. 7 yr) that is present in the atmosphere from spent fuel reprocessing

Two detector options under consideration High Pressure gas TPC • 5 -10 atm, 50 m 3 modules, 10 modules for 10 t • Xe enclosed in a non-structural bag • b range ~5 -10 cm: can resolve 2 blobs • 2. 5 m e-drift at ~250 k. V • Readout Xe scintillation with WLSB (T 0) • Additive gas: quenching and Ba++ Ba+ neutralization • Steer lasers or drift Ba-ion to detection region Liquid Xe chamber • Very small detector (3 m 3 for 10 tons) • Need good E resolution • Position info but blobs not resolved • Readout Xe scintillation • Can extract Ba from hi-density Xe • Spectroscopy at low pressure: 136 Ba (7. 8% nat’l) different signature from natural Ba (71. 7% 138 Ba) • No quencher needed, neutralization done outside the Xe

Grenoble-Neuchâtel-Padova-Zurich (Bugey reactor) liquid scintillator (veto+anti-Compton) CH 2+B reactor 18 m e steel vessel PMT v. D=2. 3 cm/ s e- anode (20 m) qreac grid 1 cm x-y plane potential (100 m) acrylic vessel +field shaping rings 1 m CF 4 gas at 3 bar cathode (-45 k. V) Pb

M U N U - proton EM shower

870 ke. V electron M U x 5 cm N y 5 cm U DX, Y = 1. 7 mm DZ = 1. 7 mm 20 cm z MUNU measures qreac and Te

Energy resolution F=0. 19, W=22 e. V s(E)/E=0. 13 % at 2. 48 Me. V ! Gotthard 5 bar xenon e-, 232 Th (from cathode), 210 Po (238 U chain) s(E)/E=3. 4 % at 1. 59 Me. V quenching ( /e-)=1/6. 5 s(E)/E= 2. 7 % at 2. 48 Me. V s(E)/E=1. 1 % at 2. 48 Me. V !

Micromegas Woven mesh stainless steel Anode with spacers Fe Fe Neuchâtel-CERN: CF 4 0 10 20 1 bar Ag pulser Ag 30 40 E(ke. V) 0 10 20 2 bar pulser 30 E(ke. V)

ITEP-Moscow, Kharkov, Neuchâtel Light detection (electroluminescence) in xenon (+CF 4? ) Grid (metallic cloth) e- track Multianode photomultiplier UV photons Anode (charge) Two gap scheme: Grid (metallic cloth) Optical fibers x-y Doped fibers : 1 step WLS UV (180 +/-20 nm) to blue or 2 step WLS with coated fibers anode Fibers (250 m)

Major effort now: liquid xenon Found a clear (anti)correlation between ionization and scintillation 1 k. V/cm ~570 ke. V

Have demonstrated that we can get sufficient energy resolution in LXe to separate the 2ν from the 0ν modes We can do ionization measurements as well as anyone ns o ti ke. V u ol 0 s Re 57 at Now we turn on our new correlation technique… 3. 3%@570 ke. V or 1. 6%@2. 5 Me. V

Fishing ions in LXe

• Prototype Scale – 200 Kg enriched 136 Xe – All functionality of EXO except Ba identification – Operate in WIPP for ~two years • Prototype Goals – Test all technical aspects of EXO (except Ba id) – Measure 2 mode – Set decent limit for 0 mode (probe Heidelberg. Moscow)

Massive materials qualification program led by Alabama with contributions from Carleton, Laurentian and Neuchatel • Approximate detector simulation with material properties to establish target activities • NAA whenever possible (MIT reactor + Alabama) • Direct Ge counting at Neuchatel, Alabama and soon Canada • High sensitivity mass spectroscopy starting in Canada • Alpha counting at Carleton and Stanford • Rn outgassing measurements starter at Laurentian (Xe plumbing) • Full detector simulation in progress

Pb Plombum VG 2 13 days 34 kg Vue-des-Alpes 400 cc germanium 2614 ke. V 208 Tl (232 Th chain)

Detector (356 on each side, 16 mm diameter 120 % QE in UV))

APD plane below crossed wire array 100 APD channels (7 APD grouped together) provide light and t 0 200 ionization channels (groups of wires 100 x +100 y) Can define fiducial volume

Drift trajectories – crossed wires

Cryostat Cross Section Outer Door Condenser FC-87 Xenon Chamber Inner Door Xenon Heater should be on this area 1” thick Thermal Insulation (MLIvacuum), not shown to scale FC-87 Xenon Chamber Support Inner Copper Vessel Outer Copper Vessel

Full detector view With Pb shielding

Do. E’s Waste Isolation Pilot Plant (WIPP), Carlsbad NM

Assuming 1) that the Xe chamber + Ba tagging gives 0 background from radioactivity. . . 2) that the energy resolution is s(E)/E=2 % (2 !) Mass (kg) 10000 Enrichment (%) 90 90 Eff. (%) 70 70 Time Background T 1/20 <m > (e. V) (yr) (events) (yr) QRPA SM 27 5 0. 3 0. 05 0. 08 2*10 28 10 5. 5 0. 02 0. 03 1. 3*10 Conclusion: With a coordinated effort, the me. V region is within reach!

Status • Enriched Xe in hand. • Clean rooms in commercial production. • WIPP agreement, including Environmental Impact, complete. • Cryostat being designed. • Xe purification and refrigeration issues being finalized • Detector vessel, readout, and electronics being engineered.