CUTAPP05 A. Caldwell/MPI

I assume you all know about 0-DBD I assume you all know about 0-DBD. We have not found a better way to test whether the neutrino is a Majorana particle. Will focus on particulars of our effort (GERDA). Topics covered: Selected review Why we chose Germanium Where we hope to improve over previous experiments Importance of background reduction Current status of GERDA

Decay rate, nuclear matrix elements If resolution poor Normalized energy spectrum If resolution good Nuclear matrix element Effective Majorana mass Phase space  Q5 0-DBD rate 1/t = G(Q,Z) |Mnucl|2 mee2

Decay rate - cont.  = (G(Q,Z) |Mnucl|2 mee2)-1 fix mee=50 meV X 1026 years reserve About factor 10 range in lifetime due to nuclear matrix elements – factor three for mee limits. Actual uncertainty  ?  Demonstrate Majorana nature. Mass determination ?

What previous experiments teach us It’s all about background, background, background How big is it ? What is the source ? And also a bit about E resol. Counts/keV/kg/day

Backgrounds - statistical analysis The discovery potential depends strongly on the background level ! Here is a Bayesian analysis assuming a flat prior for the rate (0-10-24/yr). Discovery is defined by requiring that the probability that R=0 is less than 0.0001. Just for illustration Background rate /kg/yr H-M Background K-K et al. Cuoricino

Heidelberg-Moscow Background: 0.11/keV/kg/yr 0 DBD signal ?? H.V. Klapdor-Kleingrothaus, I.V. Krivosheina, A. Dietz, O. Chkvorets (Heidelberg, Max Planck Inst.) Phys.Lett.B586:198-212,2004 Background: 0.11/keV/kg/yr 0 DBD signal ?? reserve Known Bi lines With pulse shape analysis

Heidelberg-Moscow A 4.2 signal T1/2=1.2 1025 yr

Background model in HD-Moscow (diploma thesis Christian Dörr, 2002) simulate Ge and shielding (Geant 4 + nuclear decays + gg correlations) goal: describe the measured background spectrum to extract 2 signal Comparison signal data/MC Comparison data/MC for Th calibration source Red=simulation Black = data 100 200 300 [keV] 500 600 700 [keV] reserve 900 1000 1100 [keV] result: no indication for background in Ge detector (after 5y), mainly in Cu cryostat, less in Pb 1300 1400 1500 [keV]

IGEX/Majorana Experiment Heidelberg-Moscow collaboration has insisted that external backgrounds are the main worry. Drives design decision for GENIUS, GERDA. IGEX  Majorana collaboration has stressed that eventual limit will come from radioactivity internal to Ge crystals. Cosmogenic activity was the limiting factor in IGEX (68Ge and 60Co) build detectors underground shielding uses old lead, Cu (need very low activity) pulse shape discrimination detector segmentation

Cuoricino Total mass ~41 kg 11 modules 4 detector each, 5x5x5 cm3 790 g TeO2 crystals 2 modules 9 detector each, 3x3x6 cm3 330 g TeO2 crystals +

Total Statistics: 10.85 kgxy arXiv:hep-ex/0501034 v1 Background (@DBD0): 0.18 ± 0.01 c/keV/kg/y DBD0 result: T1/2130Te <m> < [0.2÷1.1] eV > 1.8 x 1024 y reserve

NEMO3 Source in form of foils: 1 SOURCE reserve 1 SOURCE 2 TRACKING VOLUME 3 CALORIMETER Tracking volume with Geiger cells e+/e- separation by magnetic field Plastic scintillators for calorimetry and timing

NEMO3: first results Signal region First results on 100Mo (650 h) 2n spectrum Signal region reserve t1/22n (y) = 7.8 ± 0.09 stat ± 0.8 syst  1018 y t1/20n (y) > 6  1022 y Very small background, but small mass & poor energy resolution These data should be very valuable in tuning the nuclear models

Proposed experiments Some of the possible isotopes 48Ca g 48Ti Qbb = 4271 keV nat. abund. = 0.2% 76Ge g76Se Qbb = 2039 keV nat. abund. = 7.4% 82Se g 82Kr Qbb = 2995 keV nat. abund. = 8.4% 96Zr g 96Mo Qbb = 3350 keV 100Mo g100Ru Qbb = 3034 keV nat. abund. = 9.6% 116Cd g116Sn Qbb = 2802 keV 128Te g128Xe Qbb = 867 keV 130Te g130Xe Qbb = 2529 keV nat. abund. = 34% 136Xe g136Ba Qbb = 2479 keV nat. abund. = 8.9% 150Nd g150Sm Qbb = 3367 keV nat. abund. = 5.6%

Why Germanium Germanium is a good choice because: excellent energy resolution (0.1% at 2MeV). Allows finer binning, so less background. There is always the irreducible background from allowed 2 mode which can only be distinguished via energy resolution. considerable experience worldwide-Heidelberg Moscow, IGEX, Majorana. Some hope that we know background sources & can reduce it. enrichment possible (but expensive) possibilities for further development (segmentation)

Q=2.039 MeV If DBD generated ONLY by (V-A) charged current weak interaction via the exchange of three (light) Majorana neutrinos, the decay amplitude factorizes in the effective majorana mass m_ee

Engineer’s conception External backgrounds Artist’s conception Engineer’s conception Suppress 208Tl 2.615 MeV , n,  Reduce external backgrounds to 10-3/keV/kg/yr

Internal Backgrounds cosmogenic production in 76Ge at sea level: about 1 68Ge / (kg day) (Majorana white book, simulation + measurement). Considering experiments to measure cosmogenic activation. MeV From B. Swchingenheuer MPI-K Dominant decay chain: 68Ge  68Ga via EC (10.6 KeV ) =271 days 68Ga  68Zn via + (90%, 1.9 MeV) +  (0.511 MeV) =68 minutes Possibility to distinguish 2.0 MeV  + (s) from 2x1.0 MeV - ? reserve

Internal Backgrounds 60Co after 10 days of activation and 3 years of storage 0.18 mBq/kg  5.4 decays/(kg y) MeV Dominant decay chain: 60Co  60Ni via - (0.316 MeV) +  (1.17 MeV) +  (1.33 MeV) = 5.27 years Possibility to distinguish gammas from electron ? reserve +other stuff: surface contamination, supports and cables, …

Pulse shape, segmentation Can we distinguish single versus multiple energy deposits ? Tools: pulse timing, segmentation. Photon attenuation R=1/x = 4 cm for 1 MeV  Range of electrons in Germanium (from NIST tables) 68Ga + 76Ge - reserve

Developments for GERDA Water tank, Cryo tank, clean room, superstructure designs Testing & refurbishments of existing detectors - Phase I of GERDA Procurement of new detectors for Phase II Simulation studies

Infrastructures in HALL A: Super-Structure & Water tank

Infrastructures in Hall A: Super-insulated cryogenic vessel Two design studies for Cu-cryostat available: Steel-cryostat: with optimized shielding Cu-cryostat: hanging from neck Cu-cryostat: resting on pads Cu-cryostat purchase process commenced with publication in ’Supplememnt of the Official Journal of the European Union’ a ’Prior Information Notice’ - SIMAP-MPI-K 31 Jan’05 ID:2005-002331; 7 companies expressed interest Decision taking Cu vs. steel cryostat: Cu-Steel welding tests and certification

Infrastructure in Hall A: Cryogenic systems for (re-)filling and cooling Cryogenmash design Sommer design

Testing and modification of enriched detectors November, 2004, in LENS barrack (prior to barrack refurbishment) Energy resolution at 2.615 MeV ANG1 ANG2 ANG3 ANG4 ANG5 HdMo Setup 3.0 3.4 3.5 GERDA Lab, Jan.05 3.9 2.7 2.8 3.1 Notes Warm Up PA gain ‘jumps’ Co-60 source - absolute efficiency (done) Ba-133 source - dead layer thickness estimation (done) Check of ANG2 (ongoing)

Modification of enriched detectors Design study for a Cu/Si/PTFE-only detector support/contact system Minimizing mass vs. strength (current design: factor 5 safety) Alternative: Silicon support

New detectors for Phase II: Procurement of enriched Ge Ge procurement is done in two steps: procurement of 15 kg of natural Ge (‘test run’) subsequently procurement of 30-40 kg of 76Ge (‘real run’) Both samples produced in Siberia / Russian Federation 15 kg ‘test run’ (6N) Ge shipped in same way as enriched sample. Specially designed protective steel container (PSC) which reduces activation by cosmic rays by factor 20 is used for transportation Procurement of natural Ge successfully concluded; sample received at MPI Munich on March 7, 2005

MaGe simulations of muon induced backgrounds (GSTR-05-003) Implementation of Underground  energy spectrum  angular distribution Full detector geometry Energy (GeV)  cos

MaGe: MC for Gerda & Majorana 3x7 Ge crystals Electronic joint box Electronic cable Support Calibration source neck Lead shielding water tank Crystal array liquid N2 Each crystal 8x8cm, 3Z x 6 segments. LNGS: Cosmic-ray induced bg. Tübingen: muon & neutron induced bg. Heidelberg: Liquid Ar feasibility München: bg. in electronics & supports

Single electron events Most single-e events deposit energy locally. A small fraction deposit energy in 2 Ge crystal, since a hard photon is generated at early stage. Zoom Blue: electron trajectory Red: photon trajectory

Results on background rejection Rejection factors on different backgrounds: With 3Z 6 segments 1 Ge & energy in 10keV window 1 seg. & energy in 10keV window signal 90% 82% Co60 in crystal 3.0E-4 2.6E-5 Co60 in cable 1.7E-4 9.6E-6 Ga68 in crystal 9.8E-4 1.2E-4 Pb210 in crystal <1.0E-4 Tl208 in crystal 2.4E-4 5.0E-5 Tl208 in cable 2.2E-4 8.0E-5 Pulse shape analysis (PSA) is expected to reject more background and possibly save some signal.

GERDA is a work in progress: if all goes well, we should be commissioning the cryo system + existing detectors end of next year. In the 2.5 years I have been at the MPI, I have enjoyed many stimulating and fun discussions with Leo ! He has a deep intuition for physics, and a very clear way of explaining his ideas.