A dark matter candidate from extra dimensions

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9/28/06
DESY WORKSHOP The Dark Universe
A dark matter candidate from extra dimensions
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
OUTLINE

• The Model
• Z2 symmetry
• Dark matter candidate
• Coannihilation process
• Resonant channels
• Results

Collaboration with M. Serone and P. Ullio
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
Scrucca, Serone, Silvestrini '03 Panico, Serone,
Wulzer '05 Panico, Serone, Wulzer '06
THE MODEL
5D gauge theory on S1/Z2 orbifold with
gauge-Higgs unification
G SU(3)C x SU(3)W x U(1)'
In 4D by orbifold projection
G' SU(3)C x SU(2)W x U(1)Y
MATTER CONTENT Couples of bulk fermions UP
in reps DOWN in reps Chiral fermions
localized at y 0 QL, uR, bR

( Y,Y )
-
( 3,3,1/3)
( 3,6,1/3)
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
THE MODEL (2)

• Explicit tree-level breaking of the Lorentz
  SO(4,1) symmetry

• Z2 mirror symmetry

G SU(3)1,C x SU(3)2,C x SU(3)W x U(1)'1 x U(1)'2
Lagrangian invariant under the Z2 symmetry 1
2
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
Z2 MIRROR SYMMETRY
Boundary conditions A1(y 2pR) A2(y) ,
A1(-y) hA2(y) (BC)

• Linear combinations A (A1 A2 )/v2 are
  periodic / antiperiodic

• Under the mirror symmetry A A

( Y1,Y1 )
Couples charged under G1 and
neutral under G2
Same couplings

( Y2,Y2 )
Couples charged under G2 and
neutral under G1
Y (Y1 Y2 )/v2 periodic / antiperiodic
Boundary conditions as (BC)
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
STABILITY
All SM fields are even under the mirror symmetry
The lightest antiperiodic field is absolutely
stable!
If it is neutral and weakly interacting could be
a good dark matter candidate (WIMP)
New parity in a ED model different from KK parity
can provide the stability of a DM candidate
No need of Universal extra dimensions
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
WHO IS THE LIGHTEST?
Mass of antiperiodic fields
Gauge bosons
Fermions
Suppose r' lt rS and r' lt k
The n 0 mode of the gauge boson A_ is the
lighest (with mass 1/2R)
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
A_ as DM CANDIDATE
It is the analogous of the first kk mode of the
hypercharge gauge boson in UED
A_ is the gauge boson of the abelian gauge group
U(1)_
Coupling only with bulk fermions.
But SM fermions are a mixture of bulk and
boundary fermions
Annihilation cross section is (highly) reduced
At the scale allowed from EW bound (i.e. 1/R
4-5 TeV) A_ overcloses the Universe!
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
STRONG COANNIHILATIONS
Is it possible to have a WIMP with Multi-TeV
mass? Yes, if the DM candidate coannihilates with
strong interacting particles (i.e. gluons or
colored fermions)
MUED example B(1) - COANNIHILATION WITH g(1)
Burnell, Kribs '05 Kong, Matchev '05
Wh2
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
COANNIHILATION WITH g_ (without resonances)

• The mass splitting is given by the ratio rs / r'
• The production of quark pairs in s-channel do
  not suffer of the suppression due to the fermion
  localization
• The dominant cross section comes from the
  process g_g_ gSMgSM
• The running of as is negligible

Wh2
A_ can be a good DM candidate!
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
RESONANCES
Kakizaki, Matsumoto, Sato, Senami '05
q
g_(0)
_
q
g(1)
g_(0)
This process can occur since
KK number violation at tree level (at loop level
in UED)
Localized fermions
And it is resonant because
g(1) mass 2 g-(0) mass at tree level
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
COANNIHILATION WITH g_ (including resonances)
_
The decay rate of g(1) q q is
significantly higher than the mass splitting
induced by radiative corrections.
Wh2
The resonance highly increases the thermally
averaged cross section!
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Regis Marco (SISSA, Trieste)
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9/28/06
DESY WORKSHOP The Dark Universe
CONCLUSIONS

• A new Z2 symmetry (different from KK parity) can
  guarantee the stability for a DM candidate.
• The Multi-Tev mass region for a WIMP is not
  excluded since strong coannihilations and
  resonances.
• There is a significant fraction of parameter
  space in which A_ is a DM candidate with the
  correct relic density.
• Need of a fine-tuning estimation (and possible
  other coannihilation processes) to have a better
  judgment of the results.

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Regis Marco (SISSA, Trieste)