1. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 1 Béla Majorovits for the GERDA collaboration Status and plans with the GERDA experiment to probe the nature of neutrinos Max-Planck-Institut für Physik, München, Germany O U T L I N E 0νββ decay as a probe for neutrino mass and neutrino nature The GERDA experiment: Design and construction First results with enriched detectors Status and plans for phase II: new detectors ~100 physicists 19 Institutes 7 Countries

2. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 2 Neutrino oscillation experiments: Neutrinos have non vanishing rest mass! inverted normal or hierarchy ? what is the absolute mass scale? The quest for the mass of neutrinos

3. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 3 DIRAC: ν=νMajorana: ν=ν Neutrinos could be their own anti-particles: The quest for the nature of neutrinos

4. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 4 DIRAC: ν=νMajorana: ν=ν  Massive Majorana neutrinos could be responsible for the Baryon asymmetry in the universe (via leptogenesis) Neutrinos could be their own anti-particles: The quest for the nature of neutrinos

5. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 5 Neutrino is a Majorana particle Helicity flip can occur in the vertex 1/  = G(Q 5,Z) |M nucl | 2 2 0νββ decay- rate Phase space- factor Matrix element Effective Majorana Neutrino mass Neutrinoless mode of double beta decay only possible if: 0νββ decay: n n p p W-W- e-e- e-e- W-W- n n p p W-W- e-e- e-e- W-W- νeνe νeνe ν e = ν e νl νrνl νr Lepton flavor violating: ΔL=2 Effective Majorana neutrino mass contributes to 0νββ decay rate: 2νββ decay: 2nd order weak standard modell process Neutrinoless double beta decay

6. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 6 Signature: Sharp peak at Q-value of the decay 2 neutrinos escape the detector undetected: continuous spectrum Total energy of decay is deposited within detector: sharp peak Peak height not to scale! Non vanishing CP violating Majorana phases β i can supress even to zero! Effective Majorana neutrino mass: = |Σ |U ei | 2 e iβ i m i | Neutrinoless double beta decay

7. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 7 Béla Majorovits 7 Mass of lightest neutrino [eV] Effective Majorana neutrion mass [eV] 1 10 -1 10 -2 10 -3 10 -4 10 -3 10 -2 10 -1 10 -4 Bilenky and Giunti arxiv:1203.5250 0νββ decay as a probe for neutrino mass and neutrino nature Observation of 0νββ decay: Neutrino must have Majorana nature! Determination of absolute mass scale Mass hierarchy of Neutrinos Information on CP violating phases? CP violating Majorana phases could be responsible for Baryogenesis via Leptogenesis

8. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 8 Source = 76 Ge = DetectorHigh signal detection efficiency Detector material very pure (zone refinement, Czochralski growth) Very low intrinsic internal background Very good energy resolutionBackground due to 2νββ decay negligible Considerable experienceIndustrial production, improvements possible Natural abundance of 76 Ge 7,83%Enrichment necessary The quest for the mass of neutrinos

9. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 9 Location: Hall A of LNGS, Assergi, Italy 3500 mwe 9 Phase I: Use HdM and IGEX detectors Phase II: Convert 37.5 kg of enriched germanium (87% 76 Ge) into detectors GERDA : design and construction

10. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 10 Clean room Water tank with HP water and  -veto Detector array Lock system HP liquid Ar Cryostat with internal Cu shield 10 GERDA : design and construction

11. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 11 phase I Detectors (from HdM and IGEX) after dismounting from cryostats: ANG2: 2833gANG3: 2391g ANG4: 2372g ANG5: 2746g RG1: 2110gRG2: 2166g Total mass: 14.63 kg GERDA : design and construction Detectors ANG1 and RG3 started drawing leakage current after installation

12. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 12 Full phase I infrastructure for deployment of 12 detectors (all HdM and IGEX plus reference detectors) completed in May 2011 GERDA : design and construction

13. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 13 GTF 112 ANG 2 ANG 1 ANG 3 ANG 5 RG 3 ANG 4 RG 1 RG 2 Installation of phase I detectors : GERDA : Status of phase I

14. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 14 GERDA phase I of started on 1.11.11 ! Data in Energy RoI is blinded since 9th of Jan. 2012 Installation of phase I detectors : GERDA : Status of phase I

15. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 15 GERDA : Status of phase I Energy calibration of all detectors: ANG1 and RG3 are NOT included

16. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 16 GERDA : Status of phase I Live time: 152.49 days Enriched exposure: 6.104 kg∙y Duty cycle Nov. 2011 – May 2012: 78.3%

17. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 17 GERDA : Status of phase I PRELIMINARY

18. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 18 GERDA : Status of phase I Background data for enriched detectors (red) and control detectors with natural germanium abundance (blue): Background index in energy RoI for enriched detectors: (2.0 +0.6 -0.4 ) ∙ 10 -2 cts/(kg yr keV)

19. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 19  Very pronounced structures for individual energy deposits  Improved multi site recognition efficiency by A/E parameter BEGe for improved background recognition weighing potential e−e− h+h+ D. Budjas et al., JINST 4 P10007 (2009) GERDA : Status and plans for phase II current single site event: SSE time [ns] multi site event: MSE current time [ns] Background like event: Signal like event:

20. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 20 GERDA : Status and plans for phase II  5 working HP enr Ge detectors available at LNGS Transports in shielded container, storage underground The voyage of the enriched germanium

21. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 21 Signal:Background: To light detector Liquid Argon 128nm scintillation light Background rejection by detection of LAr scintillation light GERDA : Status and plans for phase II

22. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 22 Background rejection by detection of LAr scintillation light GERDA : Status and plans for phase II Two solutions (supported by MC with light tracking): SiPMs connected to fibres Low background PMTs simulations show: reduction of background to 0.001 cts/(kg yr kev) realistic

23. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 23 Background rejection by detection of LAr scintillation light GERDA : Status and plans for phase II

24. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 24 GERDA : Status and plans for phase II

25. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 25 Conclusions: Observation of 0νββ decay would have far reaching consequences GERDA phase I started on 1.11.11 Design sensitivity of phase I nearly reached Observed 2νββ decay with unprecedented signal to noise ratio PSA on BEGe detectors and LAr instrumentation will reduce phase II background by order of magnitude First phase II BE enr Ge detector crystals available at LNGS

26. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 26 BACKUP

27. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 27 EXO

28. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 28

29. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 29 GERDA : Status and plans for phase II Uncertainty of EXO 200 90% exclusion limit on 76 Ge due different to matrix element calculations

30. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 30 Plans for phase II: new detectors Background recognition powers of BEGes standard signals n+ p+ n+ surface slow pulses Data taken with 90 Y β-source  n+ surface events Identify surface events:  Low E-fields in “partially” dead layer  Slow pulses  Decrease A/E parameter 90 Y source n+ surface pulse: NSP current time [ns]

31. Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 4-11 2012 31 amplified current amplitude A PCP MSE SSE band BEGe Plans for phase II: new detectors Background recognition powers of BEGes p+ At p+ contact also e - are “visible”  A max /E is increased D. Budjas et al., JINST 4 P10007 (2009) M. Agostini et al., JINST 6 P03005 (2011) 228 Th source γ