future zero-neutrino double beta decay experiments

Steve Elliott, UK Forum 2003

Outline Neutrino Mass and General Experimental Issues The Matrix Elements The New Proposals

Future Zero-Neutrino Double Beta Decay Experiments


3 Complementary Experimental Techniques

Absolute

Mass

Scale

Relative

Mass

Scale

Mixing

Matrix

Elements

CP

nature

of ν P Pβ P

Oscil. P P

Need all three types of experiments to fully understand the nature of the ν.


Neutrino Masses

Direct mass and experiments set absolute mass scale.

<m> < 2.2 eV

The results of oscillation experiments set the relative mass scale.

Sets mν scale > 50 meV

addresses Dirac/Majorana nature of ν.


(2ν) vs. (0ν)

(2ν): Allowed and observed 2nd order weak process.

(0ν): requires massive Majorana neutrinos even in presence of alternative mechanisms.

ν

νν

e

e

e

e

n

n n

np

p

p

p


Energy Spectrum for the 2 e-

2.01.51.00.50.0Sum Energy for the Two Electrons (MeV)

Two Neutrino Spectrum Zero Neutrino Spectrum

1% resolutionΓ(2 ν) = 100 * Γ(0 ν)

EndpointEnergy


Decay Rates

Γ2ν =G2νM2ν2

Γ0ν =G0νM0ν2mν

2

G are calculable phase space factors.G0ν ~ Q5

|M| are nuclear physics matrix elements.Hard to calculate.

mν is where the interesting physics lies.


What about mixing, mν & (0ν)?

mββ = Uei2mi

i=1

3∑ εi

Compare to decay result: real ν emission

mβ = Uei2mi

2

i=1

3∑

virtual ν exchange ±1, CP cons.

No mixing: mββ =mνe=m1


Min. <m> as a vector sum

mββ=Ue12m1+eiβU

e22m2+eiαU

e32m3

<m> is the modulus of the resultant vector in the complex plane.

(In this example, <m> has a min. It

cannot be 0.)

α

Ue32m3

Ue22m2

Ue12m1

<m>

min

Figure from: PR D63, 073005


More General: 3 ν (Inverted Heir.)

30 meVor

few x 1027 yr

msmallest

<m

>

PlotThanks toPetr Vogel


More General: (Normal Heir.)

30 meVor

few x 1027 yr

PlotThanks toPetr Vogel


Physics Reach

Normal Hierarchy Inverted Hierarchy Degenerate

m1 ~ 0 meV ~55 meV = M > about 100 meV

m2 ~ 7 meV ~55 meV M

m3 ~ 55 meV ~0 meV M

<m> ~ 5 meV 28 or 55 meV M/2 or M

€

mββ ≈ 0.5( )2 m1 + ε21 0.866( )

2 m12 +δm21

2

Solar + KamLAND + Atmospheric (Ue3~ 0)


An exciting time for !

< m > in the range of 10 - 50 meV is very interesting.

For the next experiments:

mββ < δmatmos2 ≈50 meV

mi > 50 meV

For at least

one neutrino:


An Ideal ExperimentMaximize Rate/Minimize Background

Large Mass (~ 1 ton)

Good source radiopurity

Demonstrated technology

Natural isotope

Small volume, source = detector

Good energy resolution

Ease of operation

Large Q value, fast (0ν)

Slow (2ν) rate

Identify daughter

Event reconstruction

Nuclear theory

mββ ∝bΔEMtlive

⎛

⎝ ⎜ ⎜

⎞

⎠ ⎟ ⎟

14


Classes of Background

(2ν) tailNeed good energy resolution.

Natural U, Th in source and shieldingPure materials, identify daughter, pulse shape, timing, position.

Cosmic ray activation Store and prepare materials underground.


(2ν) as a Background.Sum Energy Cut Only

next generationexperimentalgoal

10-4

10-3

10-2

10-1

100

101

102

103

<m

> ( )Sensitivity meV

54321 (%)Resolution

100Mo

136Xe

76Ge

130Te

SB=me7Q

τ1/22ν

τ1/20ν δ6

2.0

1.5

1.0

0.5

0.01.00.80.60.40.20.0

Ke/Q

30

20

10

0

1.101.000.90Ke/Q


Natural Activity

The Problem:

(U, Th) ~ 1010 years

Target: ((0ν) ~ 1027 years

Detector

Shielding

Cryostat, or other experimental support

Front End Electronics

etc.


Cosmic Ray Induced Activity

Material dependent.

Need for depth to avoid activation.

Need for storage to allow activation to decay.


Evidence of 68GeFrom: NIM A292 (1990) 337-342. Experimental data from

two 1.05 kg natural detectorsIntegral of this

spectrum equals integral of this

peak.

Integral of this spectrum equals integral of this

peak.

This peak decays with the right half

life.

This peak decays with the right half

life.

ROI


Matrix Elements

There are many calculations.

Most authors quote mass limits derived from all or at least representatives of the

whole range.

How do we interpret the uncertainty associated with the mass due to the

nuclear physics?


Consider a 100 meV result.

Matrix Elementcontribution to uncertainty.

Need improvement in the Theory.

Would this exclude the inverted hierarchy with small msmallest?

Statistical contributionto uncertainty.


“Found” PeaksP

R D

45, 2

548

(199

2)

A 2527-keV Ge-det. peak that was an electronic artifact.

A ~2528-keV Te-det. peak that was a 2Statisticalflucuation.

NP

B35

(P

roc.

Su

pp

.), 3

66 (

1994

).

Need more thanone experiment


A Great Number of Proposed Experiments

COBRA Te-130 10 kg CdTe semiconductors

DCBA Nd-150 20 kg Nd layers between tracking chambers

NEMO Mo-100, Various 10 kg of isotopes (7 kg of Mo)

CAMEO Cd-114 1 t CdWO4 crystals

CANDLES Ca-48 Several tons CaF2 crystals in liquid scint.

CUORE Te-130 750 kg TeO2 bolometers

EXO Xe-136 1 ton Xe TPC (gas or liquid)

GEM Ge-76 1 ton Ge diodes in liquid nitrogen

GENIUS Ge-76 1 ton Ge diodes in liquid nitrogen

GSO Gd-160 2 t Gd2SiO5:Ce crystal scint. in liquid scint.

Majorana Ge-76 500 kg Ge diodes

MOON Mo-100 Mo sheets between plastic scint., or liq. scint.

Xe Xe-136 1.56 t of Xe in liq. Scint.

XMASS Xe-136 10 t of liquid Xe


Potential Large-Mass (~1 ton) Future Experiments

Experiments in Europe

CUORE, GENIUS

NUSEL Candidates

EXO*, MAJORANA, MOON

Smaller Mass and Development Experiments Cobra*, DCBA, NEMO*, CAMEO, CANDLES, GSO…


H.Ejiri, Y. Itahashi, N. Kudomi, M. Nomachi, T. ShimaRCNP, Osaka Univ. Japan

R. Hazama, K. Matsuoka, Y. Sugaya, S. YoshidaPhys. Dept. Osaka Univ. Japan

K. Fushimi, K. Ichihara, Y. ShichijoUniversity of Tokushima, Japan

P.J. Doe, V. Gehman, R.G.H. Robertson, O. E. Vilches, J.F. Wilkerson, D.I. WillCENPA, Univ. Washington Seattle, USA

S.R. Elliott, LANL, USA

J. EngelUniv. North Carolina, USA

A. Para, FNAL, USA

M. Greenfield,International Christian Univ., USA

M. FingerPhys. Dept., Charles Univ., Prague, Czech Republic

A. Gorin, I.Manouilov, A. RjazantsevInst. High Energy Physics, Protvino, Russia

K. Kuroda, P. Kavitov, V. Vatulin,VNIIEF, Sarov, Russia

V. Kekelidze, V. Kutsalo, G. Shirkov, A. Sisakian, A. Titov, V. Voronov,

JINR, Dubna, Russia

In Association with:

The Majorana CollaborationC. Aalseth, F. Avignone, S.R. Elliott, H. Miley…...

The MOON Collaboration:


100Mo

100Mo

100Mo

100Tc

100Ru

100Ru

100Ru

00.168

-3.034

MOON is 4 experiments…

-1.904

CC Solar ν

H. Ejiri et al. PRL 85 (2000) 2917

1.00 x 1019 y

6.1 x 1020 y

16 s-3.034

Hamish Robertson APS, April 5, 2003

?-1.293


MOON Overview

3.3 tons 100Mo, 34 tons Mo

Doesn’t require enriched material (but would probably want it).

Scintillator/source sandwich

Position and single E data play big role in (2ν) and U, Th rejection. Or

possibly bolometer

14% efficiency

ELEGANTS is precursor.


• Scintillator Mo Foil Sandwich• Mo loaded liquid scintillator• Cryogenic calorimeter

One possible configurationscintillator

Mo foilReadout fibers

1 module:Mo foil, 6m x 6m x 0.05 gm/cmScintillator 6m x 6m x 0.25cm 222 wavelength shifting fibers

Super module (detector)1950 Modules6m x 6m x 5m34 t nMo (3 t 100Mo)13600, 16-anode PMT readout

Detection Techniques under Consideration:


MOON Prototype


Cryogenic Underground Observatory for Rare Events - CUORE

Berkeley

Firenze

Gran Sasso

Insubria (COMO)

Leiden

Milano

Neuchatel

U. of South Carolina

Zaragoza

SpokespersonEttore Fiorini

Milano


CUORE Overview

0.21 ton, 34% natural abundance 130Te

TeO2 bolometers, 750 g crystals

Doesn’t require enriched material.

1020 5x5x5 cm3 crystals

25 towers of 10 layers of 4 crystals

Gran Sasso Laboratory

CUORICINO is an approved prototype (1 tower).

CUORICINO began operation in Feb. 2003


CUORE Detector

Detector Damping Suspension

Dilution Unit

ThermalShields


CUORICINO IS OPERATING

FIRST PULSE.

Data runs began In Feb. 2003


Enriched Xenon Observatory - EXO

U. of Alabama

Caltech

IBM Almaden

ITEP Moscow

U. of Neuchatel

INFN Padova

SLAC

Stanford U.

U. of Torino

U. of Trieste

WIPP Carlsbad

SpokespersonGiorgio Gratta

Stanford


EXO Overview (latter talk)

10 ton, ~70% enriched 136Xe

70% effic., ~10 atm gas TPC or LXe chamber

Optical identification of Ba ion.

Drift ion in gas to laser path

or extract on cold probe to trap.

TPC performance similar to that at Gottard.

100-kg enrXe prototype (no Ba ID)

Isotope in hand


The Majorana ProjectDuke U.

North Carolina State U.

TUNL

Argonne Nat. Lab.

JINR, Dubna

ITEP, Moscow

New Mexico State U.

Pacific Northwest Nat. Lab.

U. of Washington

LANL

LLNL

U. of South Carolina

Brown

Univ. of Chicago

RCNP, Osaka Univ.

Univ. of Tenn.

Co-SpokespersonsFrank Avignone

Harry Miley


Majorana Overview

0.5 ton of 86% enriched 76Ge

Segmented detectors using pulse shape discrimination to improve background

rejection.Prototype ready to go this fall/winter. (14

crystals, 1 enriched)

100% efficient

Can do excited state decay.

IGEX is precursor


Majorana Layout


AGe + fast n -> 68Ge + X

68Ge is the dominate background.

For 500-kg enriched detector, initiallyexpect ~500 68Ge decays/day. 1\2 = 288 d

The naturally occurring 40K in the humanbody decays at a rate of 12000 decays/second.

271 d68 m

+ 90% 10EC %

EC

68Ge68Ga

2.9 MeV68Zn

288d


Why Segmentation and Pulse Shape Analysis?

+ is pointlike.+ or Compton scattered rays deposit energy in

multiple locations.

Segmentation and PSDhelp reduce these

Backgrounds.


Recent Crystal Packaging Test (MEGA)


GErmanium NItrogen Underground Setup - GENIUS

MPI, Heidelberg

Kurchatov Inst., Moscow

Inst. Of Radiophysical Research, Nishnij Novgorod

Braunschweig und Technische Universität, Braunschweig

U. of L'Aquila, Italy

Int. Center for Theor. Physics, Trieste

JINR, Dubna

Northeastern U., Boston

U. of Maryland, USA

University of Valencia, Spain

Texas A & M U.

SpokespersonHans Klapdor-Kleingrothaus

MPI

GENIUS


GENIUS Overview

1 ton, ~86% enriched 76Ge

Naked Ge crystals in LN

Very little material near Ge.

1.4x106 liters LN

40 kg test facility is approved.

100% efficient

Heid.-Moscow experiment is precursorGENIUS


GENIUS Layout

GENIUS

DataAcquisition

Clean Room

LiquidNitrogen

Insulation

SteelVessel

12 m

Setup for operation of three 'naked’ Germanium detectors in liquid nitrogen.


The Controversy.

Locations of claimed peaks

20

15

10

5

0

Counts

20802060204020202000

Energy (keV)

16

14

12

10

8

6

4

2

0

Counts

20802060204020202000

Energy (keV)

If one had to summarize the controversy in a short statement:Consider two extreme background models:

1. Entirely flat in 2000-2080 keV region.2. Many peaks in larger region, only peak in small region.

These 2 extremes give very different significances for peak at 2039 keV.KDHK chose Model 2 but did not consider a systematic uncertaintyassociated with that choice.

Mod. Phys. Lett. A16, 2409 (2001)


Summary of ProposalsProposed ton-year

= M * T * Anticipated<mee>, (QRPA )

CUORE 0.21*5*1 = 1 60 meV

EXO 6.5*10*0.7 = 45 13 meV

GENIUS 1*2*1 = 2 20 meV

MAJ ORANA 0.5*10*1 = 5 25 meV

MOON 3.3*3*0.14 = 1.4 30 meV

The <m> limits depend on background assumptions and matrix elements which vary from proposal to proposal.


Conclusions

Research and Development are needed for all the future proposed detectors.

UG Lab space will be needed for some of that R&D.

The next generation experiments have a good possibility of reaching an interesting

<m> region.

future zero-neutrino double beta decay experiments

Documents

uk forum 2003bb2n

atmospheric n steve

eendpointenergysteve

new proposalssteve elliott

bb experiments

bb decay ratesg

neutrino massesdirect

bb daughter