The M AJORANA Experiment Ryan Martin for the LBNL M AJORANA Group NSD Monday Morning Meeting 26 April 2010

Outline Neutrinoless double-beta decay The use of 1 tonne of Germanium The M AJORANA D EMONSTRATOR Technology Developments at LBNL 2Ryan Martin, LBNL, MMM, 4/26/2010

Neutrinoless Double-Beta Decay 2  0   Neutrinoless double beta decay is a very rare process that can occur in isotopes where beta- decay is energetically forbidden Observing this requires excellent energy resolution Isotope Q % G. Gratta 3Ryan Martin, LBNL, MMM, 4/26/2010

Experimental Searches for 0  disfavored by 0  Klapdor-Kleingrothaus et al. claimed signa l Disfavored by cosmology Tonne Scale T ½ 0ν = ( G 0ν |M 0ν | 2 〈 m ββ 〉 2 ) -1 〈 m ββ 〉 ≡ U e1 2 m 1 + U e2 2 m 2 e i  2 + U e3 2 m 3 e i  3 Majorana PhasesPMNS Matrix Phase Space Nuclear Matrix Element The half life for 2  is of order years, so  is very rare if it exists A tonne scale experiment is required to probe m  of order the atmospheric mass-squared difference Klapdor- Kleingrothaus’ 6.4  claim (Mod. Phys. Lett. A 21, 1547 (2006) 4Ryan Martin, LBNL, MMM, 4/26/2010

Impact of detecting  Only practical way to see if neutrinos are Majorana particles Sets the scale for neutrino masses Allows for leptogenesis as a way to solve the matter/anti-matter asymmetry in the Universe 5Ryan Martin, LBNL, MMM, 4/26/2010

Arguments for using Germanium There are several reasons for using Germanium diode detectors (HPGe): – Source is detector – Can be enriched in 76 Ge to 86% – Low level of radio-impurities – Technology is well understood – Energy resolution is excellent (~0.2% at 2039keV) – Easy to operate (LN temperature, volume is small) 6Ryan Martin, LBNL, MMM, 4/26/2010

Towards a 1Tonne Experiment In order to build a 1 tonne Ge experiment, one must demonstrate that the required background levels can be achieved with a technology that can scale The M AJORANA and GERDA collaborations are both working to demonstrate different technologies to reduce and remove radioactive backgrounds in Ge detector arrays There is a cooperative agreement between the two collaborations to share information and come together to build an international 1 tonne Ge experiment that uses the best features from the two technologies 7Ryan Martin, LBNL, MMM, 4/26/2010

Challenges in detecting  The main challenges in detecting  are backgrounds, backgrounds and backgrounds One aims to have backgrounds of the level of 1 count per tonne per year within a 4keV Region Of Interest (ROI) around 2039keV to be sensitive to the atmospheric mass scale Need to enrich Ge to have significant quantities of 76 Ge 8Ryan Martin, LBNL, MMM, 4/26/2010

Main backgrounds Natural radioactivity in detector components (U, Th) Surface contaminants (  ) Low-energy backgrounds (Ge isotopes, 65 Zn, 73 As, 3 H; low-E compton from K, U, Th; 210 Pb brem; …) Cosmogenic radioactivity ( 68 Ge, 60 Co) Muons, fast neutrons 2  decay Neutrino scattering (reactor, solar, atm., geo, SN…) Use clean materials Go deep underground Not much you can do! 9Ryan Martin, LBNL, MMM, 4/26/2010

The M AJORANA D EMONSTRATOR 2m Pb/Cu ShieldLN Dewar Cu Cryostat Lift The M AJORANA experiment is a US-led effort that will be deployed at the Sanford lab in South Dakota The design focuses on the use of high purity material and will use a Pb/Cu shield The experiment will be run in phases and will culminate with the use of 60 kg of Ge (30kg of which will be enriched) 10Ryan Martin, LBNL, MMM, 4/26/2010

Technologies used in M AJORANA Electroformed copper Low-noise electronics and DAQ Stringent materials assays Point contact Ge detectors tests Low background detector mounts Monte Carlo simulations Various analysis techniques LBNL strongly involved! 11Ryan Martin, LBNL, MMM, 4/26/2010

Electroformed copper The use of electroformed copper removes impurities and significantly reduces backgrounds; goal is 0.3 µBq 232 Th and 238 U/kg Cu (~0.08 x g/gCu) The copper is electroformed on steel mandrels that have the same diameter as the cryostats A total of 16 baths will be deployed underground. The material from the electroformed cylinders will be machined into various components 12Ryan Martin, LBNL, MMM, 4/26/2010

Low Noise Electronics FET Fused- silica board Au/Cr pads Amorphous Ge resistor Paul Luke has developed a “low mass front end” (LMFE) board that allows one to have an amplification stage close to the Ge diode and thus reduce the noise in the signal from capacitance The resistive feedback configuration for this pre-amplier is achieved by using amorphous Germanium and the intrinsic capacitance between the pads. The large resistor also reduces noise in the signal, allowing for a low threshold Our group is testing and characterizing various implementations for this design Parylene cable FET Copper “mount” for the board 13Ryan Martin, LBNL, MMM, 4/26/2010

Electronics Development LBNL is playing a leading role in the development of the electronics for the M AJORANA D EMONSTRATOR : LMFE board Cable Characterization Preamplifier design Digitizer Card Characterization (Gretina and Struck cards) Low noise power source 14Ryan Martin, LBNL, MMM, 4/26/2010

Materials Assays I n order to determine which materials are suitable to go into the experiment, one needs to be able to assay the radio purity of materials - Several techniques and facilities are being used by the collaboration: – Gamma counting Accurate but slow and needs large samples ~ ppt U,Th at Oroville Can determine activity from all parts of a decay chain and unexpected contaminants – Neutron Activation Analysis Accurate and can use small samples Can determine activity from all parts of a decay chain and unexpected contaminants – ICP-MS (Inductively coupled plasma mass spectroscopy) accurate and can (must!) do small samples ~ <1ppt U, Th at PNNL Can only determine contributions from top parts of decay chain LBNL is responsible for the assay and characterization of the components for the low mass front end board 15Ryan Martin, LBNL, MMM, 4/26/2010

Point contact Ge detector coax GePC Ge Point contact Ge detector allow multi- site events to be identified- invented by Paul Luke (LBNL) 16Ryan Martin, LBNL, MMM, 4/26/2010

Pulse Shape Analysis 9/30/09Radford, RedTeam Review Red: all events Blue: PSA-selected events 232 Th source data The use of point contact detectors allows one to use pulse shape analysis to distinguish Multi-Site Events (MSE, background-like) from Single Site Events (SSE, signal-like) 208 Tl DEP 17Ryan Martin, LBNL, MMM, 4/26/2010

Segmented PPC Prototype – SPPC LDRD (Amman, Luke, Chan, Lesko) Segment waveform Point-contact waveform Combination of point contact and segment detector Idea is to read out both electrodes to determine the position of the events 18Ryan Martin, LBNL, MMM, 4/26/2010

Mini-PPC Detector Pin contact Contact pressure adjust To sensor/heater Temp Ref plate To cold finger IR shield base-plate Crystal mount The main purpose of the mini PPC was to study surface passivation in a conventional setup (shown here) The detector was also to used to study the low mass front end board (different configuration, not shown) as well as help to characterize the digitizing boards 19Ryan Martin, LBNL, MMM, 4/26/2010

Low Background Detector Mounts The Majorana experiment will employ detector mounts fabricated from electroformed copper in order to reduce backgrounds These are being tested at LBNL Cryostat Cold plate Detector “blank” my watch Front end board “Mercedes” mount PTFE blocks to support crystal 20Ryan Martin, LBNL, MMM, 4/26/2010

Detector Simulation The M AJORANA and GERDA collaborations have worked on the MaGe Monte Carlo simulation package (using Geant4 and ROOT) O(5) publications Pulse shape calculations also implemented Simulation and Analysis task lead is at LBNL Example: 60 Co in cryostat granularity PPC PSA 21Ryan Martin, LBNL, MMM, 4/26/2010

Pulse Shape Simulation Ryan Martin, LBNL, MMM, 4/26/ LBNL group has done work on modelling the electric field to determine pulse shapes BEGe detector from Canberra shown here simulated pulses Electric field and potential Geometry of BEGe Point contact

Digital Energy Filter Development Pulse Filter New energy digital filter was developed to correct for possible changes in the response of the front end electronics (varying pole zero correction) and improve the energy resolution Individual pulses are fit to determine the pole zero correction and the energy 23Ryan Martin, LBNL, MMM, 4/26/2010

Discreet Wavelet Analysis The Discreet Wavelet Transform (DWT) is a reversible transformation (like the Fourier Transform) that can be done on a discreetly sampled signal Unlike the Fourier Transform, the DWT contains information about the frequencies contained in a signal and when they occur 24Ryan Martin, LBNL, MMM, 4/26/2010 Can be used to tag SSE and MSE Can be used for de- noising

Majorana Sensitivity The Majorana experiment will be able to test the Klapdor claim 25Ryan Martin, LBNL, MMM, 4/26/2010

Low noise electronics and DM search Low capacitance results in very good resolution and low noise – Can look for low energy events (Dark Matter searches) The CoGeNT collaboration, has recently published a paper showing the energy spectrum in a low-threshold point contact Ge detector ( ) 2 CDMS Events DAMA/LIBRA 26Ryan Martin, LBNL, MMM, 4/26/2010

Summary  discovery would be a very compelling result 1 tonne of Ge would allow one to explore mass scales beyond the inverted mass hierarchy The M AJORANA Demonstrator will soon start to evaluate the feasibility of a tonne scale 76 Ge experiment as well as test the Klapdor claim LBNL is leading the detector development and analysis tasks for the Majorana Demonstrator and will continue to play a leadership role in the experiment 27Ryan Martin, LBNL, MMM, 4/26/2010

Backup Slides 28Ryan Martin, LBNL, MMM, 4/26/2010

The GERDA Exeperiment Ryan Martin, LBNL, MMM, 4/26/ Exp_Zuzel.pdf The GERDA experiment is a European experiment that is in the final phases of construction at LNGS The Ge diodes are immersed in LAr inside a stainless steel tank, surrounded by an instrumented tank of water The first phase of the experiment uses ~18kg of enriched Ge from the IGEX and Heidelberg Moscow experiments - in the second phase, they will have a total of 35-40kg of enriched Ge

Towards a 1 tonne Ge experiment Sensitivity depends on energy resolution, background rate and exposure: Half life (years) ~Signal (cnts/ton- year) ~Neutrino mass scale (meV) x x >10 29 <0.05<10 background rate energy resolution active mass live-time A 1 tonne experiment is well suited for exploring mass scales down to the atmospheric neutrino oscillation mass- squared difference. 30Ryan Martin, LBNL, MMM, 4/26/2010

Neutrino Mass We know from neutrino oscillation experiments that neutrinos have mass, but: We do not know the hierarchy We do not know the absolute mass scale We do not know if the neutrinos have a Majorana mass term (the only particle that could) Normal hierarchy ?Inverted hierarchy ? mass (solar, reactor) (atmospheric, LBL) ? ? ? 31Ryan Martin, LBNL, MMM, 4/26/2010

Other Experiments 32Ryan Martin, LBNL, MMM, 4/26/2010

Nuclear Matrix Elements 33Ryan Martin, LBNL, MMM, 4/26/2010

The M AJORANA and Advanced Detector Development at LBNL Staff Scientists: Alan Poon, Yuen-Dat Chan, Brian Fujikawa, Kai Vetter Engineers: Paul Luke, Harold Yaver, Sergio Zimmerman Postdocs: Jason Detwiler, James Loach, Jing Qian, Ryan Martin Undergraduate Student: Justin Tang Summer Students through mentoring program 34Ryan Martin, LBNL, MMM, 4/26/2010