Double beta decay

Ruben SaakyanUCL25 March 2004

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Outline

Motivation status Situation in the UK Future projects and UK

involvement Sensitivity and time scale

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Neutrino mass. What do we want to know?

( )

( )

Dirac

OR

Majorana

e 321

Ue12 Ue2

2 Ue32

Mixing

oscillations only

• Hierarchy (-osc and 0)• CP-violation (-osc, 0+3H)• Relative mass scale (-osc)• Absolute mass scale (0+3H+cosmology)

Superbeams-factories

~0.01 eV ~0.05 eV > 0.1 eV

degenerateinvertednormal

preferred by theorists

Double beta decay

Neutrino nature (Dirac vs Majorana) Absolute neutrino mass scale. Possible sensitivity ~0.01 eV (3H – 0.2 eV, KATRIN) IF degenerate hierarchy, we can measure “everything”

2

0

~2-3 MeV

48Ca,76Ge,82Se,100Mo,136Xe,116Cd,130Te,150Nd

Main candidates:1 20 0 0 2

1/ 2 0(0 0 ) ( , )T G E Z M m

2 222 2 i

N N

ei i ei ii i

m U m U e m

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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The Experimental Problem( Maximize Rate/Minimize Background)

Natural Activity:

(238U, 232Th) ~ 1010 yearsTarget: (0) > 1024 years

DetectorShielding

Cryostat, or other experimental supportFront End Electronics

Cosmic ray induced activity

Low-energy, ultralow-background eperiment. Overlap in experimental techniques with dark matter, solar ’s UK expertise exists

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Where are we now?

<m> < 0.35 – 0.9 eV

mscale ~ 0.05 eV mass scale from oscillation experi-ments

normal inverted degenerate ~0.01eV ~0.05eV >0.1eV (S. King et al. hep-ph/0402121)

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Heidelberg-Moscow experiment claim (end 2001)

<m> = 0.4 eV ???2.5-3

community immediate response: Claim is at least premature

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Heidelberg claim. Recent developmentshep-ph/0403018. Data acquisition and analysis of the 76Ge double beta experiment in Gran Sasso 1990-2003 accepted for publication in NIM A

71.7 kgyr

• Data reanalyzed with improved binning/summing • Peak visible• Effect reclaimed with 4.2• <m> = (0.2 – 0.6) eV, 0.4 eV best fit <m> = (0.1 – 0.9) eV (due to NME)

Problems (my view)

• Looks more like 2.5 of effect• Unknown peak at 2030 keV?• 214Bi line intensities do not match

214Bi214Bi

unkn

ow

n

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Situation in the UK At least 4 experts in UK (3

academics, 1 postdoc) UCL in NEMO – one of two

experiments currently taking data Sussex, Warwick – COBRA, new

approach R&D Meeting at RAL, Sep 2003 – Interest

decay group > 40 people from particle and nuclear communities

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Situation in the UK

steering group: Sacha Davidson, Brian Fulton, Sean Paling, Ruben Saakyan, James Stirling (chair), Kai Zuber

IPPP workshop 21-23 April. Think about tackling NME problem

strategy for UK suggested by steering group

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Where to go from here to reach 10-50 meV?A Great Number of ProposalsUK steering group suggested roadmap

CAMEO Cd-116 1 t CdWO4 crystals

DCBA Nd-150 20 kg Nd layers between tracking chambers

SuperNEMO Se-82, Various 100 kg of Se-82(or other) foil

COBRA Te-130,Cd-116 CdTe semiconductors

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

Future experiments expected to start in 2008/10(5 yr exposure)

Experiment, cost estimate

Source and Mass

Sensitivity toT1/2 (y)

Sensitivity to<m> (eV)*

Majorana$50M

76Ge, 500kg 3×1027 0.03 – 0.07

CUORE$30M

130Te, 750kg(nat)

2×1026 0.04 – 0.17

EXO$50M-100M

136Xe1 ton

8×1026 0.05 – 0.12

SuperNEMO$30M

82Se(or other)

100 kg2×1026 0.04 – 0.11

* 5 different latest NME calculations

3 m

4 m

(25 G)

B

NEMO-III SuperNEMO

COBRACdTe, CdZnTe Criteria for choosing projects

• Competitiveness • UK role• Complementarity

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Suggested Future UK programmeTwo steps: SuperNEMO and COBRA SuperNEMO

Quick start due to >15 yr of R&D experience; 40-50 meV by ~2014, likely to be first; if observed, disentangle mechanism of 0 decay

UK one of the main proponents; suggested to host in Boulby mine

COBRA Novel approach; potential for large masses;

possibility 10-20 meV by ~2020-2025; possibility to disentangle mechanism

Idea of Kai Zuber (Sussex)

Highly complementary!

25/03/2004 Ruben Saakyan, UCL PPAP meeting at RHUL

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Summary decay is indispensable for solving

neutrino mass puzzle Great interest in particle and nuclear

physics community. Highly complimentary to existing UK neutrino programme

An opportunity for UK to lead research

We may be not far away from the effect…