# Presentation: 268671

## Double Beta Decay

- •Cuore
- •Majorana
- •Dingbat

## Only way to distinguish Dirac vs. Majorana, and

**Only way to distinguish Dirac vs. Majorana, and**

## (NRC report, NESS) 

- (NRC report, NESS)

- J. W. Beeman1, E. E. Haller1,2, R.J. McDonald1, E. B. Norman1, A. R. Smith1,
- A. Giuliani3 , M. Pedretti3, G. Ventura4, M. Balata5, C. Bucci5, C. Pobes5,
- V. Palmieri6, G. Frossati7,  A. de Waard7, C. Brofferio8, S. Capelli8, L. Carbone8, O. Cremonesi8, E. Fiorini8, D. Giugni8, P. Negri8, A. Nucciotti8, M. Pavan8,
- G. Pessina8, S. Pirro8, E. Previtali8, M. Vanzini8, L. Zanotti8, F. T. Avignone III9,
- R. J. Creswick9, H. A. Farach9, C. Rosenfeld9, S. Cembrian10, I. G. Irastorza9, A. Morales10
*1**Lawrence Berkeley National Laboratory,* *2**University of California at Berkeley*
*3**Universita degli Studi dell’Insubria*
*4**Universita’ di Firenze*
*5**Laboratori Nazionali del Gran Sasso*
*6**Laboratori Nazionali di Legnaro*
*7**Leiden University*
*8**Universita’ di Milano-Bicocca*
*10**University of Zaragoza, *

**Cryogenic Underground Laboratory for Rare Events**

## Slide 5

-  Temperature signal: T = E/C  0.1 mK for E = 1 MeV

-  Bias: I   0.1 nA  Joule power   1 pW Temperature rise  0.25 mK

-  Voltage signal: V = I  dR/dT  T   V = 1 mV for E = 1 MeV

-  Noise over signal bandwidth (a few Hz): Vrms = 0.2 V

- Energy resolution (FWHM):  5 keV at 2500 keV

## Properties of 130Te as a DBD emitter

-   high transition energy ( Q = 2528.8 ± 1.3 keV )
-   encouraging theoretical calculations for 0DBD lifetime
-   already observed with geo-chemical techniques
-      (incl = ( 0.7 - 2.7 )  1021 y)

*large phase space, *
*lower background*
*(**clean window between full energy and Compton edge*
*of **208**Tl photons**)*

- <m>  0.1 eV   1026 y

**Properties of ****130****Te as a DBD emitter**

- 130Te presents several nice features:

- Isotopic abundance (%)

- Transition energy (MeV)

- 0DBD half-life (y)
- for <m> = 0.1 eV
- (different calculations)

- 48Ca

- 76Ge

- 82Se

- 96Zr

- 100Mo

- 116Cd

- 130Te

- 136Xe

- 150Nd

- 48Ca

- 76Ge

- 82Se

- 96Zr

- 100Mo

- 116Cd

- 130Te

- 136Xe

- 150Nd

- 48Ca

- 76Ge

- 82Se

- 96Zr

- 100Mo

- 116Cd

- 130Te

- 136Xe

- 150Nd

- 2

- 3

- 4

- 5

- 0

- 20

- 40

- 1024

- 1030

- 1027

- Comparison with other candidates:

## Evolution of the detectors

- Mi DBD - I

- Mi DBD - II
- CUORICINO
- CUORE

## CUORICINO sensitivity

- F0 =  4.17  1026 

-  

- a

- A

- 1/2

- M T

- b 

*Atomic mass*

*Isotopic abundance*

*Detector mass (kg)*

*BKG (counts/keV/kg/y)*

*Energy resolution (keV)*

*Running time (y)*

*Detector efficiency*

- Reasonable: b = 0.1 -  = 5 keV

- Pessimistic: b = 0.3 - = 10 keV

**F****0******** = 8.5 ******** 10****24****  ****(T=1 y) **

**F****0******** = 3.5 ******** 10****24****  ****(T=1 y) **

- <m>  **0.24** - 0.50 eV

- <m>  **0.37** - 0.77 eV

- H.V. Klapdor et al. claim: 0.11 - 0.56 eV (0.39 eV c.v.)
- Mod. Phys. Lett. A 16 (2001) 2409

- <m> (eV)

*The  lower bounds in <m****> range *
*(**0.24 eV **-** 0.37 eV**)*
*are obtained with the same *
*matrix elements calculation*
*used in this reference*

## Crystal Polishing   February 2002

## Attaching thermistors to TeO2 crystals

- Attaching thermistors to TeO2 crystals

## LBNL Roles

- 1999      Development of NTD Ge thermistors
-      2000      Assisted in construction of MiBeta upgrade
-          2001       Polishing MiBeta and Cuoricino Crystals
-               2002      Construction  of Cuoricino
-                  2003       Operation of CUORICINO
- 			& Submission of  CUORE proposal
- 	        2004-5       Design clean room for crystal fabrication
- 			   Produce NTD Ge Thermistors
- 	            2006?       First delivery of crystals for CUORE
- 		   2007?      Start of CUORE data taking

## CUORE sensitivity

-   Bulk contamination is not a problem   0.001 counts/keV/kg/y

-   Surface contamination is potentially dangerous,
-     but the amount of Cu facing the detector will be reduced by a factor 10 -100
-     with respect to now   0.01 - 0.001 counts/keV/kg/y

- Pessimistic estimation: b = 0.01 -  = 5 keV

**F****0******** = 1.1 ******** 10****26**** ******** ( T[y ] )****1/2**

**<m********> ********  66 - 140 meV ******** ( T[y ] )****1/4**** **

- Optimistic estimation : b = 0.001 -  = 5 keV

**F****0******** =3.6 ******** 10****26**** ******** ( T[y ] )****1/2**

**<m********> ********  37 -  76 meV ******** ( T[y ] )****1/4**** **

**CUORE sensitivity**

## CUORE cost estimation

**CUORE cost estimation**

## The Majorana Project

- Collaborators
- PNNL
- U of South Carolina
- TUNL
- ITEP
- Dubna
- NMSU
- U of Washington

- Industrial Partners
- ORTEC
- Canberra
- XIA
- MOXTEK
- ECP

***See ******http://majorana.pnl.gov****** for latest project info***

## Majorana Highlights

- Neutrinoless double-beta decay of 76Ge potentially measured at 2038.6 keV
- Rate of 0 mode determines “Majorana” mass of e
-               as low as 0.02-0.07 eV
- Requires:
- Deep underground location
- ~$20M enriched 85% 76Ge
- 210 2kg crystals, 12 segments
- Advanced signal processing
- ~$20M Instrumentation
- Special materials (low bkg)
- 10 year operation

## Pulse-Shape Discrimination and Segmentation for 0 -Decay

- Major cosmogenic backgrounds (60Co, 68Ge)require multiple depositions to reach ~2 MeV
- 0 -decay is essentially a single-site process
- Pulse-Shape Discrimination (PSD) radial
- Single-site depositions create current pulses populating a small area of a well-chosen parameter space.
- Multiple-site depositions are linear combinations of single-site current pulse-shapes and populate a larger area of this experimentally verified parameter space.
- Segmentation axial and azimuthal
- Single-site depositions are nearly always contained in a single detector segment.
- Multiple-site depositions usually leave energy in more than one segment, with a probability depending on segment geometry.

## Parameter-Space Pulse Shape Discrimination

- Sensitive to radial separation of depositions
- Self-calibration allows optimal discrimination for each detector
- Discriminator can be recalibrated for changing electronic variables
- Method is computationally cheap, no computed pulse libraries needed

**Single site distribution **

**Multiple site distribution**

**Notes:**
Backgrounds (60Co, 68Ge) multiple depositions to reach ~2 MeV.
0 -decay  single-site deposition.
Pulse-Shape Discrimination (PSD)
Single-site depositions create current pulses populating a small area of a well-chosen parameter space. 
Multiple-site depositions are linear combinations of single-site current pulse-shapes and populate a larger area of this parameter space. 

## Detector Segmentation

- Sensitive to axial and azimuthal separation of depositions
- Perkin-Elmer design with six azimuthal and two axial contacts has low risk
- Projected efficacy of this design is excellent with expected backgrounds

**Notes:**
Backgrounds (60Co, 68Ge) multiple depositions to reach ~2 MeV.
0 -decay  single-site deposition.
Segmentation
Single-site depositions are nearly always contained in a single detector segment.
Multiple-site depositions usually leave energy in more than one segment, with a probability depending on segment geometry.

## Moscow-Heidelberg 76Ge

- Moscow-Heidelberg **76**Ge

- Seeing is believing

- Contributed paper B7-2 This Meeting

## Projected SensitivityGround State

- GIVEN:
- Background at 2038 keV = 0.2 cts/keV/kg/y
- 68Ge decay *10x reduction*
- 60Co decay/self shielding/less copper mass *2x reduction*
- 500 kg 86% 76Ge x 10 years
- PSD+Segmentation FOM = 1.6 x 2.4 = 3.8
- RESULT:
- T0 = 4.0 x 1027 y
- <m> = { 0.020 – 0.068 } eV
- What is background was ‘zero’? (4.8 counts less)
- T0 = 2.0 x 1028 y
- <m> = { 0.009 – 0.031 } eV

## Detector R&D: Motivations 

- Double beta-decay experiments are among highest priority scientific objectives
- Experiments which measure “**energy only**” are vulnerable to backgrounds** **
- Backgrounds have been serious....
- Several nuclei must be studied to reduce systematic errors in interpretation
- Several experiments  are justifiable

- The Nygren View

- Detector R&D - David Nygren

## Next Generation

- Requirements for next generation “energy-only” experiments are daunting:
- Hundreds of kg of stuff are needed!
- Backgrounds must be reduced by 10x,  x >3 ?
- Background limited experiments: t1/4  - bad!
- Many years to establish viability
- How to establish scaling practicality...

## Alternate Idea: Use  Topology 

-  topology in magnetic field is _distinctive_
- Rejection of ,e backgrounds due to:
- Compton scatter, pair production, nuclear decay
-  decays, neutron scatters, , wimps,....
- 
- _Radio-purity issues may be much less important_

## Topologies - with magnetic field

- Compton

- Pair production (“V”  shape)

-  Decay “Dingbat”

- 

## Potentially Stronger Result

- Experimental result is an energy spectrum
- contains both 2***- and *0***-* decay events,
- contains little or no background
- Energy resolution expected to be ~1%
- Visible 0*** *peak at endpoint* if **** is Majorana*

## Concept:

- Develop imaging technique based on:
- Image capture by _ion drift_ in insulating liquid
- Strong magnetic field to visualize  topology
- Track lengths  ~1.5 cm   (Q of decay, liquid)
- Low rate experiment permits slow drift velocity
- V = ~ 2 cm/second expected @ 4 kV/cm
- Spatial resolution of ~20 m expected @ 5 cm
-  new kind of TPC-like detector

## Many Challenging Issues...

- Will topology offer useful discrimination in the presence of multiple scattering ?
- Which isotope?
- Do isotopes of interest exist in insulating liquid form with acceptable chemistry?
- Do ions display unique drift velocities?
- Can practical detector modules be made?

## Can Magnetic Bending dominate Multiple Scattering?

- Multiple scattering degrades topology -
- Rough Monte Carlo is encouraging....
- Is overall efficiency high enough to be useful?
- How high a magnetic field?
- ~2T seems OK, (event radius ~ 3mm)
- Algorithmic strategies to discard kinks due to hard scatters must be developed

## Which isotope?

- 48Ca is ideal
-  Lowest Z (20), highest Q (4.3 MeV)
- Natural abundance very low: 0.2%  problem!
- Few insulating liquids with Ca  challenge!
- Other possibilities:
- 96Zr (2.8% abundance), Z=40   , Q = 3.35 MeV
- 82Se (8.7% abundance), Z=34   , Q = 3.0 MeV

## Ion Drift in Insulating Liquids

- No basic reason why low drift velocity Vd  is inappropriate for low rate experiments
- Is ion drift velocity Vd single-valued?
- Solvation may introduce range of values...
- Ion yield may be ~1 ion pair per 200 eV
-  ~21,000 ion pairs per 0*** *decay
-  ~200 ion pairs per measurement along track

## Detector Concept

- Small signal (200e) drives readout concept
- 
- pixellated readout needed to achieve low noise
- Low Vd  low bandwidth electronics
- 
- low readout noise is possible

## Detector Concept....

**Pixellated readout plane**

- Drift 
- B field 

- Basic Module holds ~1 liter of insulating liquid
- Pixel size is ~100 x 100 m2

- HV: ~20 kV

## Summary

- Many issues to resolve, but
- Potentially very powerful approach
- Detector R&D issues not costly to explore
- Other next-generation techniques not shown to have adequate background rejection
- LBNL should support detector R&D!