Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July Béla Majorovits 7 Mass of lightest neutrino [eV] Effective Majorana neutrion mass [eV] Bilenky and Giunti arxiv: νββ 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

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

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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

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

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

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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July GERDA : Status of phase I PRELIMINARY

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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: ( ) ∙ cts/(kg yr keV)

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July  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:

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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 cts/(kg yr kev) realistic

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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July GERDA : Status and plans for phase II

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July Conclusions: Observation of 0νββ decay would have far reaching consequences GERDA phase I started on 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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July BACKUP

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July EXO

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July

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

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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]

Béla Majorovits for the GERDA collaboration ICHEP 2012, Melbourne, Australia, July 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