Baryogenesis through singlet quarks:

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• Baryogenesis through singlet quarks
• Q-genesis
• ---Self-tuning solutions---
• 
  
• 
  29. 08. 2005
• 
  COSMO-2005
• 
  Bonn
• 
  J. E. Kim
• 
  

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Long history GUTS Yoshimura,
KolbTurner Sphaleron KuzminRubakovShaposhniko
v, EW baryogenesis cosmo-05
D. Grigoriev, T. Constandin
L. Fromme, M. Seniuch
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Use global symmetry(B) Scalars Affleck-Dine,
Davidson-Hempfling Leptogenesis
lets call N-genesis, FukugitaYanagida ?-genesis
Dick-Lindner-Ratz, here B. Katlai. Q-genesis
I will talk on this now. It looks like all three
fermion geneses are constrained, but any of them
are not ruled out so far.
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• 1. Introduction
  
• 
  

2. Heavy quark

• Q-genesis by heavy quarks

4. Lifetime
5. FCNC
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1. Introduction Observed facts in astroparticle
cosmology deal with CMBR Abundant light
elements(nucleosynthesis) Galaxies and
intergalacic molecules(baryogenesis) Dark
matter and dark energy(?)
In this talk, we present a new type the
barygenesis.
H. D. Kim, K. Morozumi, JEK, PLB 616, 108
(2005).
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Sakharovs three conditions for generating ?B ? 0
from a baryon symmetric universe Existence
of ?B ? 0 interaction C and CP violation
These realized in a nonequilibrium state
GUTs seemed to provide the basic theoretical
framework for baryogenesis, because in most GUTs
?B ? 0 interaction is present. Introduction of
C and CP viol. is always possible if not
forbidden by some symmetry. The third condition
on non-equilibrium can be possible in the
evolving universe but it has to be checked with
specific interactions.
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Thus, a cosmological evolution with ?B ? 0 and C
and CP violating particle physics model can
produce a nonvanishing ?B . The problem is How
big is the generated ?B?. Here, we need
?B ? 0.6?10-9 n?
For example, the SU(5) GUT with X and Y gauge
boson interactions are not generating the needed
magnitude when applied in the evolving universe.
In the SU(5) GUT, two quintet Higgs are needed
for the required magnitude. So, GUTs seemed to be
the theory for baryogenesis for some time.
But high temperature QFT aspects changed this
view completely.
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The spontaneously broken electroweak sector of
the SM does not allow instanton solutions. When
the SU(2)W is not broken, there are electroweak
SU(2) instanton solutions. Tunneling via these
electroweak instantons is extremely suppressed,
exp(-2?/aw). This tunneling amplitude is the zero
temperature estimate. At high temperature where
the electroweak phase transition occurs, the
transition rate can be huge, and in cosmology
this effect must be considered. (Kuzmin, Rubakov,
Shaposhnikov)
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This sphaleron effect transforms SU(2) doublets.
The t Hooft vertex must be an SM singlet.
l1
l2
q1
l3
q1
B-L conserved
q1
q3
q2
q3
q2
q3
q2
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The baryon number violating interaction washes
out the baryon asymmetry produced during the GUT
era. Since the sphaleon interaction violates BL
but conserves B-L, if there were a net B-L, there
results a baryon asymmetry below the weak scale.
The partition of (B-L) into B and L below the
electroweak scale is the following if the
complete washout of BL is achieved,
The leptogenesis uses this transformation of the
(B-L) number(obtained from heavy N decays) to
baryon number. The ?-genesis also uses this
transformation.
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Thus, in some L to B transformation model, we
need to generate a net (B-L) number at the GUT
scale (Q-genesis does not need this). The SU(5)
GUT conserves B-L and hence cannot generate a net
B-L. So, for the baryon number generation one
has to go beyond the SU(5) GUT.
Three examples from fermions proposed so far 1.
Leptogenesis, 2. Neutrino genesis, 3. Q-genesis
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2. Introduction of heavy quarks
SU(2) singlets avoid the sphaleron process.
So singlet quarks survive the electroweak era.
? They must mix with light quarks so that after
the electroweak phase transition they can
generate the quark(B/3) number. ? They must be
sufficiently long lived. ? Of course, a correct
order of ?B ? 0 should be generated.
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The SU(2) singlet quarks were considered before
in connection with ? FCNC (Kang-K,
Glashow-Weinberg) ? For the recent BELLE data
(Handoko-Morozumi)
For the absence of FCNC at tree level, the ew
isospin T3 eigenvalues must be the same. Thus,
introducing L-hand quark singlets will
potentially introduce the FCNC problem. But in
most discussions, the smallness of mixing
angles with singlet quarks has been overlooked.
Since the quark singlets can be superheavy
compared to 100 GeV, the small mixing angles are
natural, rather than being unnatural.
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For definiteness, let us consider Q -1/3 heavy
quark D.
1. ?D generation mechanism 2. 10 10 s lt tD lt
1 s 3. Sphaleron should not wash out all ?D
4. Satisfy FCNC bound
Theoretically, is it natural to introduce such a
heavy quark(s)? In E6 GUT, there exist Ds in
27F. Trinification also! 27 ? 16 10 1 ?
10 5 1 5 5 1 ?
(quce) N5 (ldc) (DL2) (DcL1) N10

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When we consider this kind of vector-like
quarks, there are three immediate related
physical problems to deal with. ?Heavy quark
axion?Nelson-Barr type?FCNC
Consider one family first. It gives all the
needed features. The mass matrix is
The entry 0 is a natural choice, by redfinition
of R-handed singlets.
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It can be diagonalized by considering MM
With vanishing phases,
Since J is the doublet VEV and M is a parameter
or a singlet VEV, the mixing angle can be
sufficiently small. This is the well-known
decoupling of vectorlike quarks.
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It can be generalized to three ordinary quarks
and n heavy quarks. (3n)x(3n) matrix
can take the form by redefining R-handed b and D
fields,
For the estimate, we express J as
J f mb
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3. Q-genesis by heavy quarks Hyung Do
Kim, Takuya Morozumi, JEK(PLB616, 108, 2005)
Generation of D number is done as usual in GUTs
cosmology through the Sakharov
mechanism. In the end, D number is identified
as 3B number.
The relevant interaction we introduce is
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uc
uc
X1
ec
X1
X1, X2
uc
Dc
Dc
Plus self-energy diagrams. The interference is
needed to generate a nonvanishing D number. The
cross term contributes as
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If we allow arbitrary phases in the Yukawa
couplings, the relative phases of gD1 and gD2 can
be cancelled only by the relative phase
redefinition of X2 and X1. The same applies to
ge1 and ge2 . Thus, the phase ? appearing
is physical. The D number generated by these is
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4. Lifetime
Decay of D proceeds via
D ? tW, bZ, bH0 from which we
obtain
The lifetime of D must be made longer than 2x10
11 s. And should be shorter than 1 s.
2x10 11 s , 1 s
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This gives
The mixing of D with b is of order e. For one
period of oscillation, we expect that a fraction
e 2 of D is expected to transform to b. Since
the period keeping the electroweak phase in
cosmology is of order,
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Thus, the following fraction is expected to be
washed out via D oscillation into b,
For mD of order gt 106 GeV, we need flt10-5 . In
this range, some heavy quarks are left and the
sphaleon does not erase this remaining D number.
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5. FCNC For the FCNC, we many consider the
following
Therefore, we obtain
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Z2 symmetry
To implement a small f naturally, we can impose a
discrete symmetry. Let us introduce a parity Z2.
The discrete symmetry forbid a mixing between
doublets. We introduce a soft term, violating the
discrete symmetry, which can mix them.
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The potential is given by
The soft term violates the Z2 symmetry. If the Z2
is exact, there is no mixing of D with b and
hence D is absolutely stable lt?gt v ? 0, lt?gt
0. But the existence of the soft term violates
the Z2 and a tiny VEV of ? is generated.
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Jfmb, eJ/MD Typical values for mD
is given by constraints. The mass of ?, M?2, can
be superheavy.
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FCNC
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Here, the B-L number is that of light fermions.
So, in the neutrino-genesis, one counts the
R-handed light neutrino(?R) number also in the
B-L number. In the Q-genesis, whatever
sphalerons do on the light lepton number, still
there exists baryon number generation from the Q
decay.
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The closest similar work is DavidsonHempfling
(PLB 391, 287 (97)), where SUSY is used with B
carrying singlet scalars S, WNR (1/MT) uc
dc dc S h.c. where T is our heavy quark D. But
here D is much heavier than S.
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5. Conclusion
We presented a new mechanism for baryogenesis
the Q-genesis.
There are constraints on the parameters. There
is a reasonable parameter space for this to be
realized. With a Z2 discrete symmetry, the
smallness of the parameters is implemented
naturally.
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N-genesis and ?genesis seem to be the
plausible ones since the observed neutrino masses
need R-handed neutrinos. Survival hypothesis
sides with N-genesis. Q-genesis depends on
the unobserved Q, but this may be needed in
solutions of the strong CP problem. Also, it
appears in E6 and trinification GUTs. One
should consider all possibilities of SM singlets
and vector-like representations for BAU
N, ?R fermion singlets QLQR vectorlike
fermion NLNR vectorlike fermion with
Dirac mass, not studied
yet but certainly possible S singlet
scalar carrying B number (cf. Colored
scalars Affleck-Dine)
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• A new type baryogenesis Q-genesis
• ---Self-tuning solutions---
• 
  
• 
  25.01.2005
• 
  Cambridge
• 
  
• 
  J. E. Kim
•