Double Beta Decay:

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Annual Meeting of ENTApP N6/WP1 Milos Island (the
Cyclades in the Aegean Sea) May 20-22, 2008,
Greece

• Double Beta Decay
• A Problem of Particle, Nuclear and Atomic Physics
• Fedor Šimkovic
• Department of Nuclear Physics and Biophysics
• Comenius University, Bratislava

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Lepton Universality
Standard Model
Lepton Family Number Violation
Total Lepton Number Violation
NEW PHYSICS massive neutrinos, SUSY...
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Outline

• A nuclear physics problem
• Anatomy of the 0nbb-decay NME
• A particle physics problem
• Pion dominance in R-parity SUSY induced
• 0nbb-decay
• An atomic physics problem
• (A,Z) ? (A,Z2) eb e

Presented results obtained in collaboration with
Amand Faesler, Th. Gutsche, V. Rodin (Tuebingen
U.), J. Engel (North Caroline U.), P. Vogel
(Caltech), S. Kovalenko (Valparaiso U.), M.
Krivoruchenko (ITEP Moscow), R. Dvornický
(Comenius U.)
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I. The 0nbb-decay is a nuclear physics problem
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The 0nbb-decay NME (light n exchange mech.)
T
NME sum of Fermi, Gamow-Teller and tensor
contributions
The 0nbb-decay half-life
Neutrino potential (about 1/r12)
Induced pseudoscalar coupling (pion exchange)
Form-factors finite nucleon size
Jp 0,1,2... 0-,1-,2-...
Jastrow f. s.r.c.
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2nbb-decay nuclear matrix elements
Deduced from measured T1/22n
Differencies in NME by factor 10
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QRPA 2nbb-decay NME
Mean field
Residual interaction
H H0 gph Hph gpp Hpp
21 lev.
12 lev.
Collapse of the QRPA 21 l.m.s. 12 l.m.c
Only Bratislava-Tuebingen group
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QRPA (October 2007) F.Š, Faessler, Rodin, Vogel,
Engel 0710.2055 nucl-th, PRC 77, 045503 (2008)
r-dependence of the 0nbb-decay NME
NSM (January 2008) Menendez, Poves, Caurier,
Nowacki, 0801.3760 nucl-th
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A consistent approach for the 0nbb-decay (pairing,
short-range corr., ground state Corr. Calculated
with the same NN potential- BonnCD, Argon)
F.Š. M. Stauf, V. Rodin, A. Faessler, H.
Muether, to be submitted
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I. The 0nbb-decay is a particle physics problem
1968 Pontecorvo proposed p- ? p 2e- ,
superweak int. We identified with
R-parity breaking SUSYmechanism
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R-parity breaking mechanisms of the 0nbb-decay
massless n
MSSM
GUT constrained MSSM (mSUGRA)
Neutralino is dark matter candidate
R-parity breaking GUT constrained MSSM
0nbb-decay
massive n
Neutralino is not dark matter candidate
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R-parity Breaking MSSM (neutralino is not dark
matter candidate)
R-parity breaking terms In superpotential
Neutrino-Neutralino mixing matrix (see-saw
structure)
Radiative corrections to neutrino mass
Gozdz, Kaminski, Šimkovic, PRD 70 (2004) 095005
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I. gluino/neutralino exchange R-parity breaking
SUSY mechanism of the 0nbb-decay
quark-level diagrams
dd ? u u e- e-
exchange of squarks, neutralinos and gluinos
(l111)2 mechanism
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Hadron-level diagrams
Faessler, Kovalenko, Šimkovic PRL 78 (1998)
183 Wodecki, Kaminski, Šimkovic, PRD 60 (1999)
11507
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Squark mixing SUSY mechanism
Mixing between scalar superpartners of the
left- and right-handed fermions
A. Faessler, Th. Gutsche, S. Kovalenko,
F.Š., 0710.3199 hep-th To be published in
PRD
Hirsch, Klapdor-Kleingrothaus, Kovalenko PLB 372
(1996) 181
L
R
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Effective SUSY n-e Lagrangian
Neutrino vertex
Hirsch,Klapdor-Kleingrothaus, Kovalenko PLB 372
(1996) 181
R-parity violating SUSY vertex
Paes, Hirsch, Klapdor-Kleingrothaus, PLB 459
(1999) 450
LN-violating parameter
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Limits on R-breaking parameters
2n mode
Pion mode
A. Faessler, Th. Gutsche, S. Kovalenko, F.Š.,
0710.3199 hep-th To be published in PRD
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I. The 0nbb-decay is an atomic physics problem
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ECEC-g decay
eb eb (A,Z) ? (A,Z-2) g
?
D.Frekers, hep-ex/0506002
Sujkowski, Wycech, PRC 70, 052501 (2004)
GERDA
0.337 Q0.433 MeV Gr100 eV
T1/20ng 5 1034 years (ltmbbgt1eV)
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ECEC-gg decay (preliminary)
eb eb (A,Z) ? (A,Z-2) g g
Advanteges - both eb in 0s1/2 states (K-orbit)
- large Q values prefarable
- 1/(me(e0s k0))
enhancement Disadvantages - 2 gs in final state
(phase space) -
additional el.-mag. interaction
ltmbbgt 1eV T1/20ngg (36Ar) 5 1034 years
T1/20ngg (106Cd) 9 1032 years T1/20ngg
(162Er) 7 1032 years
Carefull study study (Merle, Lindner, Beneš, F.Š)
in progress
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0nbb-decay with emission of single electron
Dvornický, Faessler, Krivoruchenko, Šimkovic, in
preparation
(A,Z) ? (A,Z2) e e- (A,Z)
? (A,Z2) eb e- eb (A,Z) ? (A,Z2)
e (A,Z) ? (A,Z2) eb eb
signature peak at the end of single electron
energy distribution
Suppression of atomic level

• Ge/Gee 8 10-3 1/(53) (
  76Ge)
• 5 10-3 1/(63)
  (100Mo)
• 1 10-2 1/(73)
  (130Te)

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What is the nature of neutrinos?
?
theory
Only the 0?ßß-decay can answer this fundamental
question
76Ge
130Te
76Ge
82Se 150Nd
106Cd 116Cd
100Mo 150Nd
136Xe

• By product
• Absolute n mass scale
• CP Majorana phases

???