E6 GUT Models and FCNC Processes

1
E6 GUT ModelsandFCNC Processes

• Kazuki Sakurai

with S-G.Kim, N.Maekawa, A.Matsuzaki, T.Yoshikawa
(Nagoya Univ.)
Plan
I. Introduction
II. E6 GUT and Horizontal Symmetry
III. Search for E6Horizontal GUT
-- Lepton Flavor Violation
-- CPA in rare B meson decay
IV. Summary
2007/8/4 SI07_at_Fujiyoshida
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Problems in MSSM
Supersymmetry is promising candidates of New
Physics. However they have some phenomenological
problems.
Universal sfermion masses
SUSY Flavor Problem
Generally, SUSY breaking terms brake flavor
symmetry. They generate too large FCNCs.
Large SUSY breaking scale
SUSY CP Problem
Suppressed SUSY CP phases
Generally, couplings in SUSY breaking terms are
complex. Such couplings violate CP and induce too
large EDMs.
Large SUSY breaking scale
Little Hierarchy Problem
Not large stop masses
Up-type Higgs mass get a large quantum correction
which proportional to stop mass.
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Horizontal Symmetry
Flavor symmetry is natural idea, in order to
realize the universal sfermion masses.
First two generations are identified as SU(2)H
(or U(2)H) doublet. Third generation is singlet.
singlet
doublet
If SUSY breaking mediation scale is higher than
SU(2)H breaking scale, SUSY breaking terms should
respect the SU(2)H symmetry.
Universality in first two generations is realized
due to SU(2)H!!
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Horizontal Symmetry
However, if is lepton doublet
In mass eigenstate basis of fermion,
Neutrino oscillation suggest is large
mixing. Therefore large off-diagonal entries
arise after this unitary transformation.
Such large off-diagonal entries induce too large
Lepton Flavor Violation.
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E6 Unification
Guisey-Ramond-Sikivie, Aichiman-Stech,
Shafi, Barbieri-Nanopoulos, Bando-Kugo,
E6 GUT models are interesting, because
-- all one generation quarks leptons are unified
into 27.
-- realistic Yukawa hierarchies are obtained.
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E6 Unification
Guisey-Ramond-Sikivie, Aichiman-Stech,
Shafi, Barbieri-Nanopoulos, Bando-Kugo,
E6 GUT models are interesting, because
-- all one generation quarks leptons are unified
into 27.
-- realistic Yukawa hierarchies are obtained.
Cabibbo angle
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E6 Unification
Guisey-Ramond-Sikivie, Aichiman-Stech,
Shafi, Barbieri-Nanopoulos, Bando-Kugo,
E6 GUT models are interesting, because
-- all one generation quarks leptons are unified
into 27.
-- realistic Yukawa hierarchies are obtained.
up sector
down charged lepton
Cabibbo angle
Low energy three 5(Dc L) of SU(5) come from only
first two generation of 27 not 273.
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E6 Unification
Guisey-Ramond-Sikivie, Aichiman-Stech,
Shafi, Barbieri-Nanopoulos, Bando-Kugo,
E6 GUT models are interesting, because
-- all one generation quarks leptons are unified
into 27.
-- realistic Yukawa hierarchies are obtained.
up sector
down charged lepton
neutrino sector
Cabibbo angle
Low energy three 5(Dc L) of SU(5) come from only
first two generation of 27 not 273.
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Horizontal Symmetry on E6
N.Maekawa. 02, N.Maekawa, T.Yamashita 04
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Horizontal Symmetry on E6
N.Maekawa. 02, N.Maekawa, T.Yamashita 04
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Problems in MSSM
SUSY and GUT are promising candidate of New
Physics. However they have some phenomenological
problems.
Universal sfermion masses
SUSY Flavor Problem
SUSY breaking terms brake flavor symmetry
generally. They generate too large FCNCs.
Large SUSY breaking scale
SUSY CP Problem
Suppressed SUSY CP phases
SUSY breaking terms have complex coupling. Such
couplings violate CP and induce too large CPV
observables (EDMs,...).
Large SUSY breaking scale
Little Hierarchy Problem
Not large stop masses
Up-type Higgs mass get a large quantum correction
which proportional to stop mass.
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Search for E6Horizontal GUT
Next question is, how can we confirm this model
experimentally?
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Lepton Flavor Violation
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Lepton Flavor Violation
Lepton Flavor Violations (LFVs) are good process
for search the New Physics, because LFV processes
are forbidden in Standard Model.
In E6 models, LFV
processes take place with picking up the
off-diagonal entries
respectively.
We can get parameter independent prediction,
Since 10 of SU(5) contain not , final
state lepton have right-handed chirality. We can
check this by measuring angular distribution of
final state lepton.
spin


spin


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Can we discover the LFVs
at future experiments?
S.-G.Kim, N.Maekawa, A.Matsuzaki, K.S,
T,Yoshikawa 06
(exp. bound)
(exp. bound)
super-KEKB
may be discovered in KEKB or super-KEKB, If
lt 250GeV.
may be discovered in MEG, If lt 300GeV.
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CP asymmetries in rare B meson decay
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CP asym. of B?fKs, B??Ks
Time dependent CP asymmetry of B?fK, B??K are
composed of two part, B-Bbar mixing part and
direct decay part.
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Numerical Results
(preliminary)
total
total
chargino
chargino
gluino(C8)
gluino(C8)
gluino(C3-6)
gluino(C3-6)
Deviations from SM can be large(0.15)!!
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Numerical Results
(preliminary)
Scanning in SUSY CP phase
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Summary
E6Horizontal GUT models can solve some problems
in MSSM.
We analyze the Lepton Flavor Violations.
Parameter independent predictions
Final state lepton have right-handed chirality.
There are large parameter region in which LFV
decays can be discovered in near future
experiments.
lt 250 GeV
KEKB or super-KEKB
lt 300 GeV
MEG experiment
We analyze the CP asymmetry in rare B decays.
Gluino and chargino always interfere with same
sign, which makes CPA large enough to be able to
detect in future experiments.
Deviations from SM of Time Dependent CP Asymmetry
of Bd?f,? Ks
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Numerical Results
(preliminary)
total
total
chargino
chargino
gluino(C8)
gluino(C8)
gluino(C3-6)
gluino(C3-6)
chargino
gluino(C8)
Deviations from SM can be large(0.15) and non
decoupling for m !!
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Neutrinos
Right-handed neutrino masses
Seasaw mechanism
Mass scale
decouple
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Lepton Flavor Violation
Lepton Flavor Violations (LFVs) are good process
for search the New Physics, because LFV processes
are forbidden in Standard Model.
In E6 models, LFV
processes take place through the off-diagonal
entries respectively.

We can get parameter independent prediction,
Since 10 of SU(5) contain not , final
state lepton have right-handed chirality. We can
check this by measuring angular distribution of
final state lepton.
spin


spin


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Non Decoupling Features
If we raise overall SUSY scale m
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Characteristic Feature of Decay
Chirality flip is required from operator form.

• Chirality flip take place at first vertex and
  intermediate state is right-handed.
  initial lepton left-handed, final lepton
  right-handed

spin
spin
We can check this feature experimentally by
measuring the angular distribution of final state
lepton for spin direction of initial lepton.
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Numerical Results
Non decoupling features
In gt 800 GeV region,
the
Branching ratios are independent of .
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Time Dependent CP Asymmetry
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Bd ? fKs, ?Ks
Loop SM NP
SM (gtgtSUSY 3?1 transition.)
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OPE
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Gluino-Chargino Interference
Gluino
Chargino

• Chargino contribution have a same CP phase as
  gluinos one.
• Strong interference (additive or negative)

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Numerical Results
(preliminary)
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b?s? constrant
Chargino with CKM
Chargino with ?SUSY
Charged Higgs
b ? s? constraint requires large SUSY phase.
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E6 GUT
Guisey-Ramond-Sikivie, Aichiman-Stech,
Shafi, Barbieri-Nanopoulos, Bando-Kugo,
Symmetry Breaking
Fields and Rep.
E6 GUT
MSSM
generation
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E6 R parity invariant interactions
SM interactions
assumption
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E6 GUT
M.Bando, N.Maekawa. 01 N.Maekawa, T. Yamashita 02
assumption
up sector
Good for up sector due to the assumption
Bad for down and charged lepton sectors
Desired Yukawa structures are obtained in E6 GUT
model !!
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Up quark mass ?
Experiments
Models
eigenvalues
Disagreement !?
Naïve order of up quark mass is larger than the
experimental value about 10.
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FCNC induced EDM
finite
Non decoupling !
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(No Transcript)
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Gauge invariant Interactions
SU(5) invariant Yukawa interactions
SU(5) GUT relations
Not Bad
at GUT scale (1016GeV)
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SO(10) GUT
SU(5) representations
Grand Unified Theories unify not only the forces
but also matters and interactions !!