NEUTRINOLESS DOUBLE BETA DECAY ANGULAR CORRELATION AND NEW PHYSICS

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NEUTRINOLESS DOUBLE BETA DECAYANGULAR
CORRELATIONAND NEW PHYSICS
Dmitry Zhuridov Particles and Fields Journal
club Department of Physics National Tsing Hua
University
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The talk is based mostly on the paper Probing
new physics in the neutrinoless double beta
decay using electron angular correlation.A. Ali
(DESY) , A.V. Borisov, D.V. Zhuridov (Moscow
State U.) . DESY-07-097, Jun 2007. 36pp.
e-Print arXiv0706.4165 hep-ph (to appear in
Phyical Review D)
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Popularity of the theme

• M. Doi, T. Kotani, E. Takasugi,
  Prog.Theor.Phys.Suppl.83 (1985) 329
• T. Tomoda, Rep.Prog.Phys.54 (1991) 133
• S.L. Adler et al., Phys.Rev.D11 (1975)
  74
• H. Pas, M. Hirsch, H.V. Klapdor-Kleingrothaus,
  S.G. Kovalenko, Phys.Lett.B453 (1999)
  26

• SPIRES-HEP
• FIND TITLE NEUTRINOLESS DOUBLE BETA DECAY
  470
• FIND K NEUTRINOLESS DOUBLE BETA DECAY 476

• E-print arXiv Abstract NEUTRINOLESS DOUBLE
  BETA DECAY
• 1991-1995 29
• 1996-2000 139
• 2001-2005 251
• 2006-p.t. 87

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Contents

• Introduction
• Neutrinoless Double Beta Decay
• Angular Correlation in Long-Range Mechanism
• Analysis of the Angular Correlation
• Conclusion

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Introduction
SNO, Super-Kamiokande, KamLAND ? oscillations
Neutrinos have non-zero masses and they mix with
each other
Bounds on the neutrino masses
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It is largely anticipated that the neutrinos are
Majorana particles
Correspondence between Dirac and Majoana fields
Dirac field can be constructed from two Majorana
fields
Dirac field has additional freedom of phase
trasformation
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How to induce small neutrino masses?
Other possible mechanisms

• Model with scalar triplet
• Model with right-handed neutrino and scalar
  singlet
• In Zee model (with charged scalar singlet and
  additional scalar doublets) Majorana neutrino
  masses arise at one loop level
• In models with doubly charged scalar singlet
  Majorana neutrino masses arise at two loop level
• Models with effective nonrenormalizable term in
  Lagrangian

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See-saw mechanism
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Neutrinoless Double Beta Decay
n
n
Lepton number is changed by 2 units. 0?2? decay
is forbidden in the SM. Extended version of the
SM could contain tiny nonrenormalizable terms
that violate LN and allow 0?2? decay.
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• Probable mechanisms of LN violation may include
  exchanges by
• Majorana neutrinos
• Scalar bilinears, e.g. doubly charged dileptons
• SUSY particles
• Leptoquarks
• Right-handed W_R bosons etc.

• Two possible classes of mechanisms for the 0?2?
  decay
• Long range
  Short range
• (with the light ?s in the intermediate state)

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According to the Schechter-Valle theorem, any
mechanism inducing the 0?2? decay produces an
effective Majorana mass for the neutrino, which
must therefore contribute to this decay.
e
e
u
u
d
d
Purpose to examine the possibility to
discriminate among the various possible
mechanisms contributing to the 0?2? decays using
the information on the angular correlation
of the final electrons.
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Angular Distribution in Long-Range Mechanism
Most general Lorentz invariant effective
Lagrangian for the long-range mechanism of 0?2ß
decay is
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• Approximations
• leading order in the Fermi constant
• leading contribution of the parameters \epsilon
• relativistic electrons and non-relativistic
  nucleons
• S_1/2 and P_1/2 waves for the outgoing
  electrons

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Expressions for A for one ?, considered at a time
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Expressions for B for one ? at a time
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Analysis of the Electron Angular Correlation
If the nonstandard" effects, are zero then K
B01/A01. Its values are given in the Table for
various decaying nuclei of current experimental
interest
The angular correlation coefficient K for various
SM extensions for decays of
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Particular cases for the parameter space
Constraints on the couplings of the effective
LQ-quark-lepton interactions
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1a 1b 2a 2b
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Angular correlation in left-right symmetric models
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103?
103?
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Conclusion

• We have presented a detailed study of the
  electron angular correlation for the long range
  mechanism of 0?2? decays in a general theoretical
  context. This information, together with the
  ability of observing these decays in several
  nuclei, would help greatly in identifying the
  dominant mechanism underlying these decays.
• The running experimental facility that in
  principle can measure the electron angular
  correlation in the 0?2? decay NEMO3 possibly has
  no the sufficient sensitivity. The proposed
  facilities are SuperNEMO, MOON and EXO. We have
  argued that there is a strong case in building at
  least one of them.