Seesaw Neutrino mass and extra U1 symmetry

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Seesaw Neutrino mass and extra U(1) symmetry

• Rathin Adhikari
• Centre for Theoretical Physics
• Jamia Millia Islamia Central University
• New Delhi-110025

Based on Phys. Lett. B672136-140,2009
e-Print arXiv0810.5547 hep-ph
R. Adhikari, J. Erler and E. Ma
NuGoa09
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Effective Dimension five operator which
generates neutrino mass
S. Weinberg, Phys. Rev. Lett, 43, 1566 (1979)
There are three tree level realization E. Ma,
Phys. Rev. Lett, 81, 1171 (1998)

Type I
Type II
Replacing in (Type I) by
heavy Majorana fermion triplet
Type III
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Extra U(1) gauge symmetry
Consider fermion of Standard Model plus
and under new
gauge symmetry
are required to generate masses to leptons and
quarks. However some of them may be same
depending on anomaly-free solutions
Ref E. Ma, Mod Phys Lett A17, 535 (2002) E. Ma
D. P. Roy, Nucl. Phys B644,290 (2002) S.M.
Barr I. Dorsner, Phys. Rev.D 72,015011 (2005)
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(Considering three families of quarks and leptons
and
)
Conditions for absence of axial vector anomaly
(1)
(2)
(3)
(4)
(5)
Ref Adler, Phys. Rev 177, 2426 (1969) Bell
Jackiw, Nuovo Cemento, A60, 47 (1969) Bardeen,
Phys Rev, 184,1848 (1969)
Condition for absence of mixed gravitational-gauge
anomaly
(6)
Ref Delbourgo Salam, PLB 40, 381 (1972)
Eguchi Freund, PRL, 37, 1251 (1976) Alvarez-Gau
me Witten NPB, 234,269 (1984)
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From (1) , (3) (4) (which are independent of
) two solutions
Solution (I)
For
, (2) implies
No new gauge symmetry
From (5) (6) Gauge symmetry
and
are possible.
Here
Type I Seesaw
Solution (II)
From (5) (6) one solution is (a)
Type III Seesaw
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Another solution (b)
Type I III Seesaw

However, in this case to cancel anomalies
additional singlets are to be considered.
Four possible models in this case
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Radiative neutrino masses are possible here
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Model B
Model C
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X gauge boson mixes with Z boson
For zero mass mixing
which requires
for
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If X gauge boson is observed at LHC , then r
may be determined from its decay branching
fraction
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One loop radiative contribution to neutrino mass
In Model C the 3X3 Majorana neutrino mass matrix
receives tree level contribution from the
coupling of to a linear
combination of through as well as
radiative contribution from and
. This is a natural hierarchical scenario.
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Lightest particle of odd is dark matter
candidate. It may be a scalar boson - the
lighter of and
Conclusion
(1) In the context of U(1) extension of the
Standard Model we have discussed consequences of
having one or more Majorana fermion triplets
generating neutrino mass through Seesaw mechanism.
(2) Associated neutral gauge boson has
prescribed couplings to the usual quarks and
leptons in terms of and
The exclusion limit of
from low energy
data has been obtained showing that may
be accessible to LHC if is of the
order of
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(3) In case of one triplet (Model B) one Higgs
doublet couples to quark and the other to
leptons in case of two triplet (Model C) there
is third scalar doublet which allows natural
implementation of radiative neutrino mass and
dark matter.
Thank You