Universal Extra Dimension model UED and its phenomenology

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Universal Extra Dimension model (UED) and its
phenomenology
?? ?? Shigeki Matsumoto
(KEK, Theory)
Plan of my talk 1. Minimal UED model 2.
Relic Abundance of dark matter in UED 3. Indirect
detection of dark matter in UED 4. Signature of
UED at LHC 5. Signature of UED at LC
M.Kakizaki, SM, Y.Sato, M.Senami Phys.Rev.D71
(2005) M.Kakizaki, SM, Y.Sato, M.Senami
Nucl.Phys.B (2006) SM, M.Senami Phys.Lett.B
(2006) M.Kakizaki, SM, M.Senami hep-ph/0605280
(to appear in PRD)
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1.Minimal UED model
TeV-scale extra dimension model
Appelquist, Cheng, Dobrescu, PRD67 (2000) 035002
UED postulates
All SM particles propagate a compact spatial
extra dimension.
Minimal setup
From a 4-dim point of view, UED contains
M4S1/Z2
SM particles and their
KK-modes (gauge) ?, W, Z, ?(n), W(n),
Z(n) (lepton) Li, Ei Li(n),
Ei(n) (quark) Qi, Ui, Di Qi(n),
Ui(n), Di(n) (higgs) h
H(n) nth-KK particles m
n/R
R
Z2-orbifolding is required for produsing the
chiral fermion at 0-mode.
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Interactions in UED models
All interactions in UED are determined by those
in SM.
No CP Flavor problems

• e.g. Gauge interaction of fermion

4D
SM
For

KK
5D
KK expansion
(minimal) UED has only two new-physics
parameters. R Size of extra
dimension, ?Cutoff scale
UED model is treated only as an effective theory,
valid up to some high-scale ?. mUED is defined
so that the coefficients of all boundary
interactions vanish at scale ?.
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Compactification on S1/Z2
UED has KK-parity ? (-1)n Single 1st KK
cannot be produced.
Constraint on 1/R from EWPO
Constraint is not so strong compared to
other extra-dimension models. 1/R gt 300
GeV
Large Higgs mass is allowed due to the
cancellation between Higgs contribution (-) and
KK quark contributions () in rho parameter.
Lightest KK particle (LKP) is stable. UED gives
the Cold DM candidate.
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Spectrum of KK modes
Mass difference comes from radiative corrections
1st KK spectrum

1st KK 2nd KK spectrum

DM
The spectrum of 1st KK modes is quite similar to
that of super-particles in MSSM (mSUGRA).
The mass of KK-particles are degenerate in each
KK-number. (m1 1/R, m2 2/R)
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2.Thermal relic abundance of LKP dark matter
DM density per comoving volume
Dark matter is in thermal equilibrium in the
early universe
After the annihilation rate becomes smaller
than the expansion rate, the DM number
density/ comoving volume is fixed
Increasing
Freeze-out
Relic density
The relic density is determined only by the
annihilation cross section.
WMAP observation
Constraint parameter region of models.
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Calculation of LKP dark matter abundance
All 1st KK particles are degenerated in mass. ?
We have to include the coannihilation processes.

• The mass of 2nd KK particles are twice the 1st KK
  particles.
• We have to include the processes in which the 2nd
  KK
• particles propagate in the s-channel.

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Sample processes
Self annihilation
Coannihilation
The diagram of this kind is suppressed
(1-loop) but enhance by the resonance. As a
result, the contribution to the annihilation
cross section is the same as tree-level ones
S-channel resonance
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All coannihilation processes
2nd KK resonant processes
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Result (Constraint from WMAP)
DM 600 1300 GeV Higgs lt 230 GeV
All region consistent with EWPO
?R 20
M.Kakizaki, SM, M.Senami hep-ph/0605280
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Indirect detection of LKP dark matter using e
Dark matter will be detected by observing e
produced in the galactic halo.
positrons
Annihilation
DM
l
Solar system
_
DM
l
Important quantity is the annihilation cross
section into charged leptons
Galactic halo
e do not travel in straight line, the signal is
observed as the Positron excess in cosmic rays.
e is absorbed and loses its energy by the
propagation in ISM. The flux at earth mostly
originates within a few kpc.
In the case of LKP DM, the cross sections
are expected to be large !!
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Annihilation cross section into charged leptons
helilcity
helicity
S-wave annihilation
For LKP DM
For neutralino DM

• Initial state Spin 2
• (CP 1)
• No helicity suppression !!

• Initial state Spin singlet
• (CP -1)
• helicity suppression !!

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Positron signal from LKP dark matter
Hooper Kribs (2004) Hooper Silk (2005)
PAMELA
AMS-02
Near future
LKP dark matter will possibly be within the reach
of near future cosmic positron measurments. Range
(mLKP lt 900 GeV in AMS-02)
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Signature of UED at LHC
Discrimination between UED MSSM
Typical process for new physics
1stKK in UED SP in MSSM (Kinematics are
essentially same)
14 TeV
Furthermore,
P
1. The center of mass energy in each event is
unknown. 2. The momenta of (two) dark matters
in the event also unknown. (missing Energy
and moment !!)
P
New particles
Trouble in reconstruction
Difficult to discriminate UED and MSSM in the
process of this kind.
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Production of 2nd KK particles
What kind of the process should we focus on ?
What is a main difference between UED MSSM ?
I. Difference of spins between 1st KKs
Super-particles.
II. Existence of higher KK particles,
especially 2nd KK particles.
we can discriminate them
Difficult !! (the reason is same as those in the
previous slide.)
Production of 2nd KK
particles. (Among those particles, 2nd KK mode of
electroweak gauge bosons are
important because they decay into high-energy
leptons.)
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2nd KK gauge boson (Z(2) ?(2)) production and
detection
Production process for 2nd KK bosons
P
P
1-loop process
q
V2
Q2
(KK-parity 1 !!)
V2
P
P
Indirect
Direct
Detection of 2nd KK boson
L
?2, Z2 ? ll processes. (clean signal,
reconstruction) V2 decays are fully visible
V2
-
L
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Analysis of the LHC reach for Z2 ?2
They consider the inclusive production of Z2 ?2
and look for a dilepton resonance in both ee-
and µµ- channels.
Dilepton mass resolution in CMS detector ?mee/mee
1 (constant) ?mµµ/mµµ 0.0215 0.0128(mµµ/1
TeV)
The signal eficiency varies from 65 at 1/R 250
GeV and 91 at 1/R 1 TeV
The SM background have been calculated with the
PYTHIA generator.
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LHC reach (result)
Datta, Kong Matchev hep-ph/0509246
The total integrated luminosity L required for a
5s excess of signal over
background in the dilepton channels, as a functin
1/R.
DY ----- Direct production ALL ----- Direct
Indirect
One year running at low luminosity L 10
fb-1 Several years running at high lum. L 300
fb-1
In addition to the search for 2nd KK discovery,
1st KK search will be also performed.
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Diresonance structure in UED
The 2nd KK gauge bosons are a salient feature of
UED, however these resonance is not sufficient
discriminator.
Because it resembles an ordinary Z.
Can we discriminate UED and these models?
An important evidence in favor of UED is the
simultaneous discovery of several,
rather
degenerate, KK gauge boson resonances.
SUSY also accommodate multiple Z gauge bosons,
there is no good motivation behind their mass
degeneracy.
Direct only
Direct only
1/R 500 GeV
1/R 500 GeV
We can separately discover 2nd KK gauge bosons as
individual resonances !!
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Signature of UED at LC
After the discovery of the signatures in LHC, LC
will confirm the model beyond SM and determine
the new physics parameters precisely.
KK quarkonium
In UED, important quantities are masses of KK
particles.
I. 1st KK leptons ? direct pair production
II. 2nd KK gauge bosons ? 2nd KK resonances III.
1st KK quarks ? 1st KK quarkonium resonances
?(1)
e
L(1)
e
q(1)
q
?
Z(2)
q
e-
e-
q(1)
L(1)
1-loop
?(1)
I. 1st KK leptons (2 SM leptons E)
II. 2nd KK gauges (2 SM leptons E)
III. 1st KK quarks (2 SM quarks E)
These resonances does not appear in
supersymmetric models.
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Cross sections for creating KK particles
Battaglia, Datta, De Roeck, Kong, Matchev
hep-ph/0502041
K.Fujii, M.Kakizaki, SM, N.Okada, T.Yamashita
hep-ph/0608xxx
(pb)
ee- ?Z(2)? µµ- E
ee- ?b(1)b(1)? bb- E
ee- ? µµ- E
1/R 700 GeV
1/R 700 GeV
1/R 500 GeV
D
Includingbeam eff.
Includingbeam effects
S
s1/2(GeV)
s1/2(GeV)
s1/2(GeV)
Parameters such as mass of KK particles are
determined precisely by observing the threshold
regions. ? Beyond the UED model
c.f. SUSY s?ß3 at threshold region, no sharp
peak due to resonance
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Summary

• From the EWPO and thermal relics arguments, the
  compactification scale will be 600 lt 1/R 1300 GeV
  if UED is realized as physic beyond the SM.
• We can expect the strong signals in (near future)
  detection experiments of DM, especially in the
  indirect detection using e.
• LHC can cover the interesting region of the
  compactification.
• For confirming the model and searching high
  energy physics beyond UED, we need a multi-TeV
  linear collider.
• Using the collider, we can determine model
  parameters and mass spectrum by the measurement
  of threshold productions of KK particles.

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Properties of 2nd KK modes of electroweak gauge
bosons
Mass and Width of 2nd KK gauge bosons
MASS
Width
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Production process for 2nd KK bosons.
Direct production
Indirect production
P
P
1-loop process
q
V2
Q2
V2
P
(KK-parity 1 !!)
P
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Decay products of 2nd KK gauge bosons
Branching fractions are weakly Sensitive to 1/R.
P
Authors use the process ?2, Z2 ? ll
processes. (clean signal, reconstruction)
V2
P
V2 decays are fully visible
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Contrasting SUSY and UED at CLIC (Multi-TeV
collider)
Battaglia, Datta, De Roeck, Kong, Matchev,
hep-ph/0502041

• Comparison of

in UED
with
MSSM parameters are adjusted to UED parameters
in SUSY

• SM background

• Event seletion

• missing energy gt 2.5 TeV
• transverse energy lt 150 GeV
• event sphericity gt 0.05

(small polar angle)
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Angular distribution and spin measurements
UED
Spin 1/2
Factor
SUSY
Spin 0
at
signal background
signal
From Battaglia, Datta, De Roeck, Kong, Matchev,
hep-ph/0502041
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Discrimination of UED from SUSY

• Photon energy spectrum in

• Cross section for

resonance
Includingbeamstrahlung
From Battaglia, Datta, De Roeck, Kong, Matchev,
hep-ph/0502041
c.f. SUSY at threshold region, no
sharp peak due to resonance