CP violation in seesaw mechanism

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CP violation in seesaw mechanism
International Conference on the Seesaw Mechanism
(SEESAW25) 10-11
June 2004, Institut Henri Poincare, Paris.

• Junji Hisano (ICRR, Univ. of Tokyo)

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1, Introduction
Neutrino oscillation Finite, but small neutrino
mass
Seesaw model (Introduction of
right-handed neutrinos )
Baryon in Universe Leptogenesis (B-L violation
by Majorana mass )
Unification of Matter in SO(10) GUT
Superheavy We need Supersymmetry (SUSY)
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Charged Lepton-Flavor Violation in SUSY seesaw
model
Non-vanishing LFV slepton masses by radiative
correction
(BorzumatiMasiero)
And then,
The charged LFV,
, may be observed in near future experiments.
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SUSY GUT with right-handed
neutrinos
Matter unification GUT relation in flavor
physics
Colored Higgs
Flavor Higgs
( generic CP phase in GUT)
(moroi)
Flavor-violating right-handed current might
predict deviation of and so
on.
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Contents of my talk

• Introduction
• CP violation in SUSY seesaw model
• CP violation in SUSY SU(5) GUT with right-handed
  neutrinos
• Summary

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2, CP violation in SUSY seesaw model
Non-vanishing LFV slepton masses by radiative
correction
and where
Radiative decay processes
Sizable effect
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Bottom-up approach to seesaw model
Degrees of freedom of physical observables
In Seesaw model, M33, 6,CP4(mixing)2(Major
ana)
In (Hermitian) Real 6,Phase3
In light mass matrix M3, 3,
CP1(mixing) 2(Majorana)
We can take and for
parameterization of seesaw model, and neutrino
and charged lepton experiments give independent
information of seesaw model.
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CP violating observables in leptonic sector

• T-odd asymmetry in LFV decay,
• It depends on a a Jarlskog invariant,
• Electric dipole moments of electron and muon.
• When right-handed neutrino masses are
  degenerates,
• EDMs are suppressed so much, similarly to
  neutron EDM
• originated from CKM phase.
• However, if they are not degenerate, EDMs are
  proportional to

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T-odd asymmetry in LFV decay,
T-odd asymmetry in polarized muon decay.
This is smaller than 24. Various
contribution to and asymmetry
comes from the interference. (photon and Z
penguin, and box diagrams) However, photon
penguin tends to dominate due to phase space.
Thus, when and photon penguin
is suppressed accidentally, T-odd asymmetry is
sizable.
polarization vector
(Gouvea, Lola, Tobe)
Jarlskog inv.
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Branching ratios and T-odd asymmetry
(Ellis, JH, Lola, Raidal)
Accidental cancellation enhances T-odd asymmetry.
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Leptonic EDMs
Threshold correction to slepton mass due to the
non-degeneracy of right-handed neutrinos
enhances the leptonic EDMs. One-loop
correction to and .
(Ellis, JH, Raidal, Shimizu)
(Farzan and Peskin)
Thus,
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CP violation in SUSY SU(5) GUT with right-handed
neutrinos
the neutrino Yukawa induces the flavor violating
right-handed currents, ex,
Here, is the CP phase in colored Higgs
interaction. CP and flavor violation in the RH
currents give rich hadron physics
(2.7 sigma deviation observed in Belle
experiments.)
(1,2) mixing and (2,3) and (1,3) mixings are
constrained by and hadronic EDMs,
respectively.
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Hadronic EDMs
Current bounds on Mercury and neutron EDMs
constrain the SUSY models.
Choromoelectric dipole moments (CEDM) generate CP
violating hadron interaction, which generates
EDMs of Mercury and neutron.
Strange quark component in necleon is not
negligible. From baryon mass and sigma term in
chiral perturbation theory,
Thus, hadronic EDMs depend on the strange quark
CEDM via K or eta meson interaction.
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Hg atom EDM
199
Hg is a diamagnetic atom, and the EDM is
sensitive to CP- violating nuclear force induced
by pion and eta exchange, which generates T-odd
EM potential (Shiff momentum). Recent evaluation
of Shiff momentum reveals that contribution to
EDM from isoscalar channel for meson exchange is
suppressed by 0.01 compared with previous
estimate. From it, it is found that the strange
quark CEDM contribution comes from pi-eta
mixing.
(JH, Shimizu)
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Neutron EDM
This evaluation is a difficult task. The QCD
sum rule is useful for evaluation of only
contribution valence quarks. Here, we present
our result by a traditional calculation of the
loop diagrams.
(JH, Shimizu)
Strange quark contribution to neutron EDM is not
suppressed.
Here, Peccei-Quinn symmetry is assumed. Axion
suppresses strange quark CEDM contribution for
valence quarks, while above formula is not
changed so much even if no PQ symmetry.
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Hadronic EDM constraint on in SUSY
GUT
If the off-diagonal term in has a CP
phase, it contributes to CEDM in the
cooperation with the left-handed squark.
The off-diagonal terms in are induced
by the top quark Yukawa coupling with CKM.
Enhanced by heavier fermion mass
In typical model, the left-handed squark mixing
induced by top quark are
Here,
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Constraints on the flavor violation in squark
mass term
From neutron (Hg atom) EDM
(JH, Shimizu)
Constraints on (1-3) and (2-3) mixing for the
right-handed squark Mixings are stringent.
(1-2) mixing is constrained by and
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CEDMs in SUSY SU(5) GUT with right-handed
neutrinos
For
(JH, Kakizaki, Nagai, Shimizu)
Here, diagonal right-handed neutrino mass matrix
is assumed, and then parameters in neutrino
sector are given by oscillation data.
New technique for deuteron EDM may reach to This
corresponds to and
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Non-negligible may lead to the
deviation of CP asymmetry
since is a radiative
processes. The dominant contribution comes from
the gluon penguin diagram in the broad parameter
space.
The effective operator for induced
by
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CP asymmetry in v.s. Strange
quark CEDM
CP asymmetry in and strange
quark CEDM are strongly correlated.
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Assuming
(JH, Shimizu)
The neutron EDM bound is one or two orders of
magnitude stronger for a sizable deviation in
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Summary
Seesaw mechanism is the most fascinating model
for neutrino mass. However, it is difficult to
reconstruct it from the neutrino oscillation
data. In the supersymmetric extensions, the
flavor and CP violating processes are important
for the purpose. In this talk, we show the
aspect of the CP violation. In the SUSY
seesaw mechanism, CP violating observables are
T-odd asymmetry in lepton decay and leptonic
EDM. However, they tends to be suppressed except
for accidental cases. In the extension of SUSY
GUT, right-handed squark mixings are generated by
the neutrino Yukawa interaction. The hadronic
EDMs are good probes for (1-3) and (2-3) mixing
of the right-handed squark mixing. New deuteron
EDM measurement may give more stringent
constraints on them or find the signal.